Refractive Surgery (Instant Clinical Diagnosis in Ophthalmology)

Instant Clinical Diagnosis in Ophthalmology Refractive Surgery INSTANT CLINICAL DIAGNOSIS IN QPHTHALMOWGY REFRACTIVE...

Author: Garg Ashok | Rosen Emanuel | Goes Frank Jozef | Bovet Jerome Jean | Pajic Bojan | Wang Yan

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Instant Clinical Diagnosis in Ophthalmology

Refractive Surgery

INSTANT CLINICAL DIAGNOSIS IN QPHTHALMOWGY

REFRACTIVE SURGERY Series Editors Ashok Garg MS PhD FI AO(Bel) FRSM FAIMS ADM FICA International and National Gold Medalist Chairman and Medical Director Garg Eye Institute and Research Centre 235-Model Town, Dabra Chowk Hisar-12500S

Emanuel Rosen MD Medical Director Rosen Eye Associates Harbour City, Salford Quays M503 BH

UK

In di a

Editors Frank Jozef Goes MD Medical Director Goes Eye Centre W Klooslaan 6 B 2050 Antwerp Belg ium

Jerome Jean Bovet MD Consultant Ophthalmic Surgeon FMH , Clinique de L'oei l 15, Avenue Du Boi s-de-Ia-Chapelle CH-1213,Onex Switzerland

Bojan Pal Ie MD Chief of the Corneal and Refractive Surgery Department Vision Care, Klinik Pallas, Louis Giraud Sir. 20 4600 Clten Switzerland

Yan Wang MD Professor Tianjin Medical University Director, Refractive Surgery and Vision Correction Centre, Tianjin Eye Hospital and Eye Institute, No.4, Gansu Road Tianjin 300020 Ch ina

8elquiz A Nassaralla MD PhD Consultant Ophthalmic Surgeon, Department of Cornea and Refractive Surgery , Goiania Eye Institute, GOiania, GO Brazil

Foreword Jorge L Alia

JAYPEE BROTHERS MEDICAL PUBLISHERS (P) LTO New Delh i · Ahmedabad· Bengaluru • Chennai • Hyderabad • Kochi Kolkata • Lucknow • Mumbai • Nagpur

PUbfisfJeq ..by

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USA Office 1745, Pheasant Run Drive, Maryland Heights (Missouri), MO 63043, USA, Ph: 001-6366279734 e-mail: [email protected]. [email protected] Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) © 2009, Editors All rights reserved. No part of this publication should be reproduced, stored in a retrieval system , or transmitted in any form or by any means: electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the editors and the publisher. This book has been published in good faith that the material provided by contributors is original. Every effort is made to ensure accuracy of material , but the publisher, printer and editors will not be held responsible for any inadvertent error(s). In case of any dispute, all legal matters are to be settled under Delhi jurisdiction only. First Edition: 2009 ISBN 978-81-8448-452-6 Typeset at JPBMP typesetting unit Printed at Ajanta Offset & Packagings Ltd., New Delhi

Preface In modern day busy and fast life ophthalmologists are glued to their clinical

and surgical practice and have little time to read large volume books. The need of hour is to have pocket size ready recokners enriched with complete and upto-date information of the diseases in a comprehensive manner. At present very few quality ready reference books are available at an International level. After detailed research regarding the needs of ophthalmologists, we have developed a series of 10 Volume ready reference books termed as Instant Clinical Diagnosis in Ophthalmology. Th is series covers Oculoplastic and Reconstructive Surgery, Retina, Lens, Glaucoma, Refractive Surgery, Pediatric Ophthalmology, Strabismus, Anterior Segment diseases, cornea and Neurophthalmology. Present series has been designed to provide up-to-date information of concerned disease in a comprehensive and a lucid manner along w ith high quality clinical photographs in an easy to read format. International Masters of concerned subject have contributed chapters in this series covering Pathophysiology, clinical signs and symptoms, Investigations, differential diagnosis, treatment and prognosis in a simiplified manner. Present volume has been formatted with an aim to provide complete up-todate information about state-of-art Corneal Refractive Surgery and high tech Lenticular refractive surgery under one roof in a compreh ensive manner. Basic

optics and physiology of Refractive errors, advanced Surface Ablation procedures (PRK, Epilasik, Lasek, SBK), Lasik Surgery (Aspheric, customized and wavefront Presbyopic), Phakic rOLs (AC and PC Phakic IOLs, Multifocal lenses, ICL and customized IOLs), Presbyopic surgery lenses (Accommodating and Aspheric lenses) and complications have been covered beautifully by International panel of experts in this field. We are highly thankful to our publisher M/ s Jaypee Brothers Medical Publishers (P) Ltd. specially ShJitendar P Vij (CEO), Mr Tarun Duneja (Director of Publishing) and all staff members for their dedication and hard efforts put in the preparation of this high quality series of Instant Clinical Books. We hope this 10 volume set of ready reference pocket size books shall provide complete and useful clinical information to ophthalmologists all around the world and shall help them to accurately and precisely diagnose, treat and manage their clinical case confidently to the satisfaction and expectations of their valued patients. We also hope this ready reckoner shall serve as useful companion on every clinician's desk. Editors

Contents Section 1: Corneal Refractive Surgery 1. Refractive Errors of the Eye ......................................................................... 2 Grove fD, David Meyer (South Africa) 2. Basic Optics of Refractive Surgery ........................................................... 10 Yan Wang, Ming Liu, Kanxing Zhao, Lihua Fang, Feng Rao, fie Hou (China) 3. Pathophysiology of Various Refractive Errors Like Myopia, Hyperopia, Astigmatism, Accommodation and Presbyopia .............. 18 Ahmad K Khalil ( Egtjpt) 4. Orbscan .......................................................................................................... 24 Amar Agarwal, Nilesh Kanjiani, Athiya Agarwal, Sunita Aganval, Ashok Garg (India) 5. Photorefractive Keratectomy with Mitomycin C for High Myopia ........................................................................................... 36 Belquiz A Nassaralla, foao f Nassaralla fr (Brazil) 6. Photorefractive Keratectomy after Penetrating Keratoplasty ............ 42 Belquiz A Nassaralla, foiio f Nassaralla fl" (Brazil) 7. Phototherapeutic Keratectomy on Recurrent Corneal Erosions ....................................................................... 46 Belquiz A Nassara lla, folio f Nassaralla fr (Brazil) 8. Myopic Photorefractive Keratectomy Using Solid State Laser .......... 50 Nikolaos S Tsiklis, George D Kymionis, George A Kounis, Ioannis G Pallikaris (Greece) 9. Photorefractive Keratectomy for Residual Myopia following Radial Keratotomy .................................................................... 62 Belquiz A Nassaralla, foiio f Nassaralla fr (Braz il) 10. Recent Advances in Photorefractive Keratectomy ............................... 70 C Banu Casar (Turkey) 11. Painless EpiLASIK ...................................................................................... 80 Chu Renyuan, Zltou Xingtao, Wu Ying (Ch ina) 12. Wavefront-guided Photorefractive KeratectomyToday and the Future .................................................................................. 86 Weldon W Haw, Edward E Manche (USA) 13. Presby-EpiLASIK in Pseudophakic Eyes with the Wavelight Allegretto ................................................................... 92 Frederic Hehn (Fra nce)

xx Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) 14. EpiLASIK with Mitomycin C ................................................................... 110 D Ramamurthy, Chitra Ramamurthy (India) 15. One-shot Epithelium-rhexis: Personal Technique ............................. 118 Roberto Pinelli (Italy) 16. Surface Ablation after Laser In Situ Keratomileusis; Retreatment on the Flap ........................................................................... 126 Jeroen JG Beerthuizen (Netherland) 17. Wavefront Analysis and its Clinical Significance .............................. 130 Yan Wang, Lihua Fang, Boyan Li, Kanxing Zhao (China) 18. Wavefront LASIK ...................................................................................... 134 Mark Wevill, Emanuel Rosen (UK) 19. Aspheric Ablation with Nidek Platform ............................................... 148 S Bharti IIndia) 20. Costumized Excimer Laser Treatment Using the Wavelight Allegretto Eye Q Laser .......................................................... 156 Johan A de Lange (South Africa) 21. Advances EpiLASIK and LASEK ........................................................... 192 Bojan Fajic (Switzerland) 22. Wavefront Optimize and Astigmatism correction with the Allegretto Excimer Laser .......................................................... 202 Jerome Jean Bovet, Auguste Chiou (Switzerland) 23. Aberropia: A New Refractive Entity ...................................................... 214 Amar Agarwal, Nilesh Kanjiani, Soosan Jacob, Athiya Agarwal, Sunita Agarwal, Tahira Agarwal, Ashok Garg (India) 24. Topographic and Aberrometer Guided Laser ..................................... 226 Amar Agarwal, Sunita Agarwal, Athiya Agarwal, AS/10k Garg IIndia) 25. Refractive Change after RK ..................................................................... 236 Frank JozefGoes (Belgium) 26. LASIK Complications and Management .............................................. 242 Yan Wang, Wenxiu Lu, Kanxing Zhao, JinZing Yu, Jianmin Gao (China) 27. Cross-linking Plus Topography-guided PRK for Post-LASIK Ectasia Management .................................................... 258 A John Kanellopoulos (Greece) 28. PRK for Low to Moderate Myopia ......................................................... 270 Michael 0' Keefe, Caitriona Kirwan (Ireland) 29. LASEK Procedure with the Use of Mitomycin C ................................. 276 Iwona Liberek, Justyna Izdebska (Poland) 30. Transepithelial Cross-linking for the Treatment of Keratoconus ....................................................................... 286 Roberto Pinelli, E Milani (Italy) 31. Sub Bowman's Keratomileusis: Combining the Best of PRK and LASIK for Optimal Outcomes ................................................................ 292 Daniel S Durrie (USA)

Contents

xxi

32. cTEN™- Custom Transepith elial "No-touch, One-step, All-laser" Refractive and Therapeutic Ablations with the iVISTM suite .............................................................................. 312 Carlo Francesco Lovisolo, Charles Wm Stewart (Italy) 33. Astigmatism ................................................................................................ 330 Frank Jazef Goes (Belgium) 34. Customized LASIK for Presbyopia: PMLTM (Presbiopic Multifocal LASIK Technique) ........................................... 334 Roberto Pinelli (Italy) 35. Amblyopia .................................................................................................. 348 Frank JozefGoes (Belgium) 36. Laser Scleral Ablation for True Accommodation for Presbyopia ............................................................. 352 JT Lin (Taiwan) 37. Solid State Lasers for Refractive Surgery ............................................. 360 Emanuel Rosen (UK), Tarak Pujara (Australia) 38. Dry Eye after Refractive Surgery ............................................................ 394 Belquiz A Nassaralla, Joao J Nassaralla Jr (Brazil) 39. Corneal Biomechanical Properties ......................................................... 402 Jorge L Ali6, Mohamed H Shabayek (Spain) 40. Future of LASIK Surgery .......................................................................... 406 Arun C Gulani, Tracy Schroeder Swartz (USA)

Section 2: Lenticular Refractive Surgery 41. Refractive Management of Hyperopia ................................................. 416 Ahmad K Khalil (Egypt) 42. Restoration of Accommodation by Capsular Bag Refilling .............. 420 Okihiro Nishi, Kayo Nishi, Yutaro Nishi, Shiao Chang (japan) 43. Custom ICLs ............................................................................................... 430 Carlo Francesco Lovisolo (Italy) 44. Mini Incision IOL Implantation-Current Scenario .......................... 448 Roberto Bellucci, Simonetta Marselli (Italy) 45. Monofocal HOA Free IOL to Correct Secondary Presby-LASIK ..... 456 Frederic Hehn (France) 46. Man aging Intraoperative Floppy Iris Syndrome ................................ 470 David F Chang (USA) 47. Artisan, Toric Artisan an d Artiflex Phakic Intraocular Lenses ........ 478 Johan A de Lange (South Africa) 48. Orthok eratology ......................................................................................... 504 Antonio Calossi, Carlo Francesco Lovisolo (Italy) 49. Aspheric IO Ls (Wavefront Based IOLs) ............................................... 518 Sanjay Chaudhary (India)

xxii

Instal1t Clinical Diagl10sis ill Ophtllnllllology (Refractive SlIrgenJ)

50. Dual Optic Accommodative IOLs .......................................................... 528 GU Auffartll (Germany) 51. Anterior Chamber Phakic IOL with Angle Fixation ........................... 532 Juan C Rocco (Argentina) 52. Advacnes in Microphakonit for Refractive Lens Exchange (MIRLEX)-A New Technique ............................................................... 542 Arturo perez-Arteaga (Mexico) 53. Blue Light Filtering Intraocular Lenses ................................................. 554 Swati Piluljllele, Lalit Alok, Anand Aga rwal, Tanuj Dada (India) 54. Refractive Lens Exchange: Current Perspectives ............................... 560 T Howard Fine, Richard S Hoffman , Mark Packer, (USA ) 55. Advances in Optic Designs to Reduce PCO ......................................... 574 WoifBuehl, Oliver Findl (Austria) Index ...... ............... ............................... ... ...................................................... 583

5

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~J

ION

1 Refractive Errors ,. of the Eye Grove JD, David Meyer (South Africa)

INTRODUCTION

A refractive error (ametropia) is defined as failure of parallel light rays to focus on the retina w ith the eye in a non-accommodating state. Three conditions of ametropia are found , namely myopia, hypermetropia and astigmatism. Although not adhering to the true definition of ametropia, presbyopia (agerelated inadequacy of accommodation) is often included. MYOPIA Optical Principles

Parallel light ra ys focus anterior to the retina. Axial myopia - axial length too long for the optical power of the eye, e.g. posterior staphyloma, buphthalmos. Refractive (index) myopia -Optical power too strong for the axial length of the eye, e.g. keratoconus, nucleosclerosis, lenticonus, spherophakia. Clinical Signs and Symptoms Symptoms

Decreased ("blurred") vision for distant objects Asthenopia "Squinting" (piJ1hole effect). Signs

Decreased visua l ac uity Visual field - Contracted Ring scotoma An terior segment - Cornea might be slightly larger Anterior chamber deep Lens -Early cataract formation common abnormalities, e.g. spherophakia, lenticonus occasional phacodonesis. 2

Refractive Errors of the Eye

Fig. 1: Myopia- Parallel light rays ente ring the eye come to a point focus anterior to the retina

Fig. 2: Hype rmetropia- Parallel light rays entering the eye come to a point focus posterior to the retina

Sturm's conoid

Fig. 3: Astigmatism-The optical power of the eye varies in different meridians thus replacing a focus point with orthogonal focus lines (StOrm's conoid)

3

Ills tall t Clillical Diagl/osis ;" Opirtlralmologrj (Refractive SlIrgenj) Fundus: Disc -

Large Tilted Myopic crescent Choroidal crescent Tesselated Chorioretinal atrophy Lacquer cracks Coin hemorrhages Choroidal neovascu lar membranes

Fuch's spots Complications: Staphylomas - macula hole foveal retinoschisis Peripheral degenerations with retinal hole formation. Rhegmatogenous retinal detachment.

Physiological myopia - associated with nor ma l growth of th e refractive components of the eye resulting in mild to moderate nearsighted ness. Pathologic myopia -excessive growth of the axial length with normal growth of other componen ts of the eye resulting in severe nearsightedness. INVESTIGATIONS

Visual acuity - Near Distance

Pinhole test, Potential aguity (PAM) Refraction - Objective Subjective Visual fields Biomicroscopy - An terior segment and dilated fundus examination. Corneal topograph y Pach ymetry Anterior chamber depth analysis Wavefront aberometry. Differential Diagnosis

Hysteria Drugs - Anticholinesterase Pathologic myopia - Choroideremia Gyrate atrophy Diffuse choroida l atrophy Progressive bifocal chorioretinal atrophy. 4


5

E "'c o

Decline in amplitude of accommodation

'~

'S;

ro

~ 10

'0 C

'0

"- 20

ro

~ 40

Presbyopia

o

10

20

30

40

50

60

70

Age in years

Fig. 4: Presbyopia- Difficulty or discomfort with near vision tasks due to age related reduction in accommodation amplitude and subsequently near point of clear vision

\

5

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) Treatment

Spectacles Contact lenses Surgical- Corneal surgery - Radial Keratotomy (RK) - Laser refractive - Laser-assisted in situ kera tomileusis (LASIK) Laser assisted sub-epithelial keratomileusis (LASEK) Photorefractive Keratectomy (PRK) - Onlays and Inlays - Epikeratoplasty - Intrastromal Ring Segments - Intraocular surgery - Phakic IOL - anterior chamber posterior chamber - Clear Lens Extraction with or without multifocal intraocular lenses. Prognosis

Physiological myopia - usually stabilized by the age of 21 years. Pathologic myopia - tends to progress with or without resultant complications. prognosis dependant on type and degree of pathology. HYPERMETROPIA Optical Principles

Parallel light rays focus posterior to the retina. Axial hypermetropia - Axial length too short for the optical power of the eye. Refractive hypermetropia - Optical power too weak for the axial length of the eye, e.g. aphakia, microphthalmos, cornea plana. Clinical Signs and Symptoms

Symptoms: Decreased (blurred) vision especially for near objects. Asthenopia Signs: Decreased visual acuity Anterior segment: - Cornea plana Anterior chamber might be shallow Fundus: Disc - Small Crowded Shot silk retina Vessels - Tortuosity Abnormal branching Types: Total: (hypermetropia under total cycloplegia) Latent - Disguised by ciliary muscle tone Manifest - Facultative - correctable by accommodation Absolute - remaining hypermetropia not correctable by accommodation. 6

Refractive Errors of tile Eye Investigations

Visual acuity

- Near - Dis tance

Pinhole tes t, PAM Refraction - Objective - Subjective - Cycloplegic Biomicroscopy - Anterior segment and dil ated fundus exa mination. Gonioscopy Corneal topography Pachymetry Anterior chamber depth analysis Wavefront aberometry. Differential Diagnosis

Drugs Tumors

- cycloplegics - Orbital - In traocular.

Macular edema Treatment

Spectacles Con tact lenses

Surgica l - Laser refractive - LASIK LASEK

PRK - Corneal surgery

- Onlays and Inlays - Thermokeratoplasty

- Intraoc ular surgery

- Phakic IOL

-

Keratophakia Epikeratoplasty Laser Cond ucti ve

- Anterior chamber - Posterior chamber

- Clear Lens Extrac tion Prognosis

Good prognosis with all modalities of treatment. Increased risk of angle closure glaucoma. Ea rly onset presbyopia.

7

Installt Clillical Diagnosis ill Opl.thall11ologlJ (Refractive SurgenJ! ASTIGMATISM Optical Principles

Optical power of the eye varies in different meridians thus rep lacing a focus point w ith orthogonal focus lines (Sturm's conoid). Regular as tigmatism - principal meridians 90° to each other. Oblique astigmatism - meridians not near 90° and 180°. Irregular astigmatism - principal meridians not at 90° to each other. Clinical Signs and Symptoms

Symptoms: Decreased vision. Asthenopia Signs: Diagnosed during objective or subjective refraction an d corneal topography. Simple astigmatism - one meridian = emmetropic other meridian ;:::: either myopic or hypermetropic

Compound astigmatism - both meridia either myopic or hypermetropic Mixed astigmatism -one meridian myopic and the other hypermetropic. Investigations

Visual acuity

- Near - Distance

Pinhole test, PAM Refraction - Objective - Subjective Biomicroscopy - Anterior segment and dilated fundus examination. Corneal topography Pachymetry Anterior chamber dep th analysis Wavefron t aberometry. Treatment

Spectacles Contact lenses Surgical - Laser refractive - Corneal surgery

8

LASIK, LASEK, PRK (wavefront guided) Transverse keratotomy Arcuate Keratotomy Thermokeratoplasty - Laser - Conductive Intraocular surgery - Toric Phakic 10L - anterior chamber - posterior chamber - ToricJOL during cataract surgery -

InstalltClinical Diagllosis ill Ophthall1lo1oglJ (Refractive SurgenJ) ASTIGMATISM Optical Principles

Optical power of the eye varies in different meridians thus replacing a focus point with orthogonal focus lines (Sturm's conoid). Regular astigmatism - principal meridians 90° to each other. Oblique astigmatism - meridians not near 90° and 180°. Irregular astigmatism - principal meridians not at 90° to each other. Clinical Signs and Symptoms

Symptoms: Decreased vision. Asthenopia Signs: Diagnosed during objective or subjective refraction and corneal topography. Simple as tigmatism - one meridian = ernmetropic other meridian = either myopic or hypermetropic Compound astigmatism - both meridia either myopic or hypermetropic Mixed astigmatism - one meridian myopic and the other hypermetropic. Investigations

Visual acuity

- Near - Distance

Pinhole test, PAM Refraction - Objective - Subjective Biomicroscopy - Anterior segment and dilated fundus examination. Corneal topography Pachyrnetry Anterior chamber depth analysis Wavefront aberometry. Treatment

Spectacles Contact lenses Surgical - Laser refractive - Corneal surgery

8

-

LASIK, LASEK, PRK (wavefront guided) Transverse keratotomy Arcuate Keratotomy Thermokeratoplasty - Laser - Conductive Intraocular surgery - Toric Phakic IOL - anterior chamber - posterior chamber - ToricIOL during cataract surgery


Prognosis Regular astigmatism - Good prognosis with all modalities of treatment. Irregular astigmatism - Hard contact lenses or Keratoplasty required.

PRESBYOPIA Optical Principles Difficulty or discomfort of near vision due to age related reduction in accommodation amplitude.

Clinical Signs and Symptoms Symptoms: Decreased vision for near objects/ tasks. Asthenopia Signs: Decreased near visual ac uity. Decreased amplitude of accommodation.

Investigations Visual acuity

- Near - Distance Pinhole test, PAM RAFrule Refraction - Objective - Subjective Biomicroscop y - Anterior segment and dilated fundus examination. Corneal topography Pach ymetry Anterior chamber d epth analysis.

Differential Diagnosis Drugs - Parasympatholytics Tranquilizers Neurologic disorders - encephalitis closed head trauma.

Treatment Spectacles

- Reading . Multifocal/ progressive Contact lenses - Multifocal monovision Surgical - Laser refractive- LASIK - Corneal surgery - Intraocular surgery

- Monovision presby-LASIK - Thermokeratoplasty - Accommodative IOL Diffractive multifocal IOL Refractive multifocal IOL.

9

2 Basic Optics of Refractive Surgery Yan Wang, Ming Liu, Kanxing Zhao, Lihua Fang, Feng Rao, Jie Hou (China)

LIGHT, PHYSICAL OPTICS, GEOMETRICAL OPTICS

Light is a part of e lectromagnetic wave, and electromagnetic wave is a travelin g tran sverse wave of electric and magnetic fi eld. Physical optics views light as waves. Three principa l charac teristic of a wave are its wavelength, amplitude and frequen cy. Wavelength is determined by the distance between the nearest crests of the wave (A,). Amplitude is the maximum value attained by the electric field as the wave propagates (A ), determining the inten sity of the wave. Frequency is the number of wave crests tha t pass a fixed point per second. Geometrical optics conceives of ligh t as ra ys and en ables us to deal w ith the imaging properties of lenses and mirrors. REFLECTION, REFRACTION, DIFFRACTION, SCATTERING OF LIGHT

At the optical interface, the direction of the reflected ray bears a definite relation ship to the direction of the inciden t ray. 111e angle between the incident ray and th e norma l is known as the angle of incidence. The angle between the reflected ray and the normal is known as the angle of reflection . The law of reflection states as following: 1. The reflected ray lies in the sa me plan e with the incident ray and the surface normal; 2. The an gle of reflection equ als the angle of the incidence. As light passes from one transparent medium to another, its speed and bends are changed. The angle between the light ray and the normal is called the angle of refraction. The law of refraction consists of two parts: 1. The incident ray, surface normal and refracted ray lie in the same plane; 2. The an gle of incidence is related to the angle of refraction by the following formula: nj sine; = n, sine, Where: " i is the refractive index of the medium the light is leaving; OJ is the incident angle; II , is the refractive index of the medium the light is entering;O,is the refractive angle. 10

Basic Optics of Refractive SlIrgenj

1

A

_I

Fig . 1: Electromagnetic wave

n, n,

Fig . 2: Reflection and refraction

11

Instant Clillical Diagnosis ill Ophthalmology (Refractive Surgery) In the eye, the refraction shows the ability of the eye to bend light so that an image is focused on the retina. Diffraction is the slight bending of light as it passes around the edge of an object. All waves are subject to diffraction when they encounter an obstruction, an aperture or other irregularity in the merliurn. The mount of bending depends on the relative size of the wavelength of light and the object. The shorter the relative size, the less the diffraction is. Scattering of light occurs at irregularities in the light path, such as particles or inclusions in an homogeneous medium. Scattering caused by very small particles, such as the molecules in the atmosphere, is called Rayleigh scattering. Rayleigh sca ttering is generally very weak, and it varies according to wavelength, with greater at shorter wavelengths. The sky appears blue because blue light from the sun is scattered more than sunlight of longer wavelengths. Larger particles, such as dust in the air, scatter light more intensely and w ith less dependence on wavelength. ABERRATION, WAVEFRONT ABERRATION, CHROMATIC ABERRATION

In paraxial optics, all paraxial rays focus to a point. With nonpar axial rays,

the focus is not stigmatic. Deviations from stigmatic imaging are called aberrations.

A wavefront is a surface along the light path that contains all points of equal phase. Light from a point object will emit perfectly spherical wavefronts. When these wavefronts go through an optical system, the wavefront curvature is changed. If the optical system is perfect, the wavefronts that leave the exit pupil are also perfectly spherical; if the optical system is aberrated, the wavefronts that leave the exit pupil are also aberrated. The difference between the perfectly spherical wavefront and aberrated wavefront is wavefront aberration. Aberration that results in distortion of color is called chromatic aberration. There are two types of chromatic aberration. Longitudinal chromatic aberration is the inability of optical system to focus different wavelengths of light onto the exact same focal plane. Transverse chromatic aberration is caused by the optical system magnifying different wavelengths differently. EMMETROPIA, MYOPIA, HYPEROPIA, PRESBYOPIA

Emmetropia is the refractive state in which parallel rays of light from an object at infinity focus exactly onto the retina. The far point of the emmetropic eye is at infinity, and infinity is conjugate with the retina.

12

Basic Optics of Refractive SlIrgenJ

Fig . 3: Diffraction

Fig. 4: Chromatic aberration

Fig. 5: Emmetropia

13

Jllsta/lt Clinical Diagnosis ill Ophthalmol0:5lJ (Refractive SurgenJ)

In myopia, para llel light rays from an object at infinity con verge too soon and thus focus m front of the reti na, forming a blurred image on the retina. The far pomt of ti1e eye is in frontof the eye, between the cornea and optical infinity. In h yperoPIa, parallel hght rays from an object at infinity focu ses behind the retma. The vIrtual far point of the eye is behind the retina. Presbyopia is the gradual loss of accommodati ve response resulting from loss of elasticIty of the lens. Accommodative amplitude diminishes inexorably WIth age. It becomes a clinical problem when the remaining acco mmodate amplItude IS msuffi Clent for the patient to read and carry out nea r-vision ta sks.

CURVATURE, RADIUS OF CURVATURE At position s, the curvature is the magnitude of the change in w1ite tangent vector per W1i t change in distance along the curve, which is defined by: x:(s) = I dT~;s))1

Where, the vector T being a unit vector has no dimension; that is, it is W1affected by a lllliforn1 change in scale of aUcoordinates. s is a length; therefore dT - has the dimension of the reciprocal af a length, that is, of the reciprocal of

ds

a distance.

The radius of curvature is the reciprocal af curvature, which is a length. If the curvature is 0, a straight line, the radius of curvature is infinite, or wldefined .

Refractive surgery ma y involve altering the curvature of the cornea. Q-FACTOR, PROLATE, OBLATE

The curvature of an ellipsoid can be expressed as an asphericity quotient, called the Q-facta r. The Q-factor far a sphere is 0, the Q-factor for a prolate ellipsOid is negati ve and the Q-factor for an oblate ellipsOid is positive. OPTICAL AXIS, VISUAL AXIS

The human eye is not a centered optica l system. The optica l axes af the cornea and lens are not coincident (i.e. the centers of curva ture of their refracting surfaces do not all fall on one straight line). Nevertheless, we can define an approximation to the optical axis of the eye as the straigh t line that by best fit passes closest to all of the centers of curvature. The visua l axis is usually defined as the broken line that connects the fixation point with the fovea and passes through the nodal points.The fovea of the retina is not on even the approxin1ate optical axis of the eye. The visual axis of the eye extends from the fovea through the nodal point of the eye and out throug h th e cornea to an object, a poi.nt at "infinite" distance, such as a star. 14

Basic Optics a/Refractive SlIrgenJ

Fig. 6: Myopia

Fig . 7: Hyperopia

Aspherical surface

Spherical surface

Prolate shape

f\\

0=0 Radius (mm)

Oblate shape

~ 00

Fi g. 8: Q -fac tor

15

Illstallt Clillical Dingllosis ill OplttlwlmologtJ (Refractive SlIrgenJ) MTF, PSF

The modulation of an image is defined as modulation

Lmax - Lmin Lmax + Lmill

Where Lmax and Lmill are the nlaximum and minimum lunlinance of the

image, respectively. The modulation transfer function (MTF) is d efin ed as the modulation of the image M, divided by the modulation of the object M o' M. MTF= - '

Mo

Modulation transfer function is a quantity representing a relationship between the sample and result image. Consider a very small point of light. If the visual system had perfect optics, the image of this point on the retina wou ld be identical to the original point of light. However, the eye's optics is not perfect. So the point has a blurred image on the retina, and the relative intensity of the image is distributed across the retina, which is d efined as a function of d istance, called the po int spread fun ction (PSF).

16

Basic Optics of Refractive SlIrgenJ

Fig. 9: Visual axis and optical axis (a) Center of pupil , (b) Center of cornea , and (c) Visual axis

17

3 Pathophysiology of Various Refractive Errors Like Myopia, Hyperopia, Astigmatism, Accommodation and Presbyopia Ahmad K Khalil (Egypt)

18

Inability of the human eye to bring a focused image on the retina in various situations w ith subsequent blur and visual discomfort is the hallmark of various refracti ve errors. Hyperopia occurs \,,,hen the rays come to a focus behind the retina, myopia when the rays come to a focus in front of the retina. 111 astigm atism, rays come to differen t foc i due to difference in the power of the eye in diffe rent meridians, and in presbyopia, the eye is unable to bring rays emanating of near objects to focus on retinal level. The commonest cause of hyperopia is probably a shortened eye; eyes with short axial lengths. Flat keratometric readings and decreased refractive index of the lens are other causes. A combination of several factors often co-exist. In younger age, much of the hype ropia can usually be corrected by the patient's own accommodation, which ll1creases the effecti ve power of the eye brin ging incident rays to a focus on the retinal leve l (facultative hyperopia). With advancing age the accommodative effort cannot be sustained and symptoms of hyperopia with blurring and eyestrain become more and more manifest. Symptom atic h yperopia are trea ted by glasses, con tact lenses. As explained else were in this book, laser vision correction is useful for hyperopia degrees up to plus 6.0. Phakic lens implanta ti on and refractive lens exchange are suitable for higher degrees. Long axia l length, increased curvature of the cornea and increased refractive index of the lens are main causes of myopia. Blurring of distance vision is u niversal and proportionate to the degree of myopia. Patients with lower degrees of myo pia have the advantage of clear near vision, as the divergent rays from the near object come to focus on the retina with no need for accommodative effort or need for correction. This is an added ad van tage ll1 middle age, negating the ll1Cidents of presbyopia. Concave lenses in glasses or contacts help bring the raise to focus back on the retina laser vision correction is very useful in correcting myopia degrees

PatilOphysiologtj of Variolls Refractive Errors Like Myopia, Hyperopia

Focal point is behind the retina

Fig. 1: Hype ropia

Focal point

~~~:;:;;;!~i"-- is in fron t

of the retina

Fig. 2: Myopia

Multiple focal

~~~~~~"'-_ points· images -

on retina are blurry

Fig. 3: Astigmatism

19

Instal/t Clinical Diagnosis ill OplrtlralmologtJ (Refractive SlIrgenJ)

up to -10.0. Phakic lens implantation and refractive lens exchange are suitable for higher degrees. Difference in power in various axes is casused mainly by corneal curvature errors. Commonest cause is congenital curvature astigmatism. Others involve

keratocon us, scarred cornea, surgica lly induced, and lenticonus. [n simple astigmatism, the focus in one axis fa lls in the retina, and in front or behind the retina in the perpendicular axis. In compound astigmatism, both foci lie together in front or behind the retina, while in mixed astigmatism, one focus lies in fron t and the other behind the retina. H orizon tal corneal diameter (12 mm) is slightly larger than its vertical diameter (11.5 mm), with co-incide nt sli ght fla ttening of the horizontal meridian. This is caused by the continuous movement and slight pressure of the eye lids increasing the vertica l curvature in most subjects by about 0,12 D. Therefore, astigmatism associated with increased curvature of the vertical merid ian is called 'with the role astigma tism", expressed in horizontal lninus cylinder. Astigmatism can be treated with both glasses and hard contact lenses. Soft toric contact lenses are often less satisfactory because of the potential rotation-movement of the lens on the eye surface. Laser vision correction is usually very effective in ma naging asti gmatism not associated with other corneal pathology. Recently, toric ICLs began to be used satisfactorily. ACCOMMODATION AND PRESBYOPIA

The ability of a distance-corrected human eye to see at near depends on 2 components; true accommodation (o ptical change in power of the eye), and to a lesser extent; pseudo-accommod ation caused by increased depth of field (myopic astigmatism, vertical coma and other highe r order aberrations; HOAs and Pinhole vision) Theories of Accommodation

Along the centuries and up to this very moment, many theories have sprung out to explain the actions taken by the eye to change its power and bring images of near objects to proper focus on the retina. Theories involving changes in lens thickness, consistency, elasticity or changes in Ciliary muscle contracti lity or distribution of fibers, or changes in zonular fibers have been proposed. The most accep ted theories discussed in recent literature are the time honored Helmholtz theory and the new Schacher theory. Helmholtz Theory was proposed in the mid-nineteen th century, and with minor modifications, has stood the test of time. Developing modern techniques have 20 proven many of its constituents. Briefl y, contraction of the ciliary muscle

Pathophysiology of Various Refractive Errors Like Myopia, Hyperopia

Fig . 4 : Helmholtz theory of accommodation

Fig . 5: Schacher theory of accommodation

21

Installt Clinical Diagllosis ill Oplrthalmologtj (Refractive SlIrgenj) causes narrowing of the ciliary mu scle ring with relaxa tion of zonu lar fibers and subsequent decrease in the lens equatorial diame ter, an increase in lens

axial thickness, and the lens anterior and posterior central surfaces undergo an increase in curvature of the elastic lens increasing its power. Loss of accommod ation is mainly caused by senile hardening of the lens substance, preventing it from changing shape. In the mid 1990s, Schacher proposed his new theo ry of accommodation. He suggested that equatorial zon ules insert into the an terior cil iary muscle at the root of the iris, while an terior and posterior zonules insert into the posterior ciliary bod y. During ciliary mu scle con tracti on, it curls toward the sclera at the iris root increasing tension on the equatorial zonular fib ers (opposite ac tion to that in Helmholtz theory!), and releasing tension on the anterio r and posterior zonular bund les, causing flattening of the peripheral lens surfaces w hile increasing the central anterior and posterior lens surface curva tu res. Modern investigatin g techniques, however, like UBM, high resolution M RI have, however, proven severa l of the compone nts proposed by H elmholtz, like re lease of zonular tension during accommodation, lens equatorial movement away from sclera with accommodation. Zon ular fiber d istribu tion proposed by Schacher could not be demonstrated in humans. Failure of Accommodation ; Presbyopia

With growing age, the amplitude of true accommodation decreases, beginning early in life-in childhood or adolescence. Typically, between the ages of 38 and 43 years, these changes reach the stage at which accommodative loss is sufficien t to cause the blurred-vision symp toms of p resbyopia. The word presbyopia is based on a Greek word that means "aging eye". Incipient Presbyopia: It rep resents the earliest stage with nocturnal presbyopia (wider pupil with less dep th of foc us), distance blur fo llowing near work. This d istance blur is caused by a slowed response of the lensciliary body com plex during relaxa tion from near foc us (which has been attained with considerable effort). Typica lly, the patien t's history suggests a need fo r a reading additio n, but the patient perfo rms well visuall y on testing and, given the choice, ma y actuall y reject a near vision prescription. Functional Presbyopia: The age at which presbyopia becomes symptomatic varies. So m e patients are symptoma tic at an earlier age (premature p resbyo pia); others later than ex pecte d, largely d ue to va r ia tion s in environment, task requirements, o r nutrition. Absolute Presbyopia : As a result of the continuous grad ua l decline in 22 accommod ation, functional p resbyopia progresses to absolute presbyopia.

Pathophysiology of Various Refractive Errors Like Myopia, Hyperopia

Absolute presbyopia is the condition in which there is virtually no accommodati ve ability. SimjJar to accommodation, the etiology of presbyopia remains elusive in many aspects. There are theories incriminating the lens and its capsule, ciliary muscle and choroid, or changes in the geometry of zan ular fibers attachment. The lens has won the most theories and duly so for ca using presbyopia. Changes in its sagittal thickness, equator diameter, degree of anterior curvahu e, internal lens structure (decrease in nucleus ref index, increase in water soluble crystallins), Lens Biomechanics; (sclerosis), capsule thickness, and atrophy of the ciliary muscle have been proposed with various levels of evidence. [n the past decad e, refractive su rgeons have gone through various innovative approaches to tackle presbyopia, often calling it ' the last frontier" using various approaches; corneal approach (presby LASIK) playing on the theme of increasing pseudo-accommodation. Platforms are being developed by various researchers, and achieving reasonable success rates. Lenticular app roa ch invol ves impl anta tion of accommodative and pseudoaccommodative lenses. Scleral expansion surgery have also been tried based on the concept of Schacher in which lost accommodation is caused by equatorial expansion of the lens. Thls surgery, however, have met ve ry limited wd-long-term success so far.

23

4 Orbscan Amar Agarwal, Nilesh Kanjiani, Athiya Agarwal, Sunita Agarwal, Ashok Garg (India)

INTRODUCTION

Keratometry and corneal topography with placido disc systems were originally invented to measure anterior corneal curvature. Computer analysis of the more

complete data acquired by the latter has in recent years has been increasingly more valuable in the practice of refractive surgery. The problem in the placido disc systems is that one cannot perform a slit scan topography of the cornea. This has been solved by an instrument called the Orbscan that combines both slit scan and placido images to give a very good composite picture for topographic analysis. Bausch and Lomb manufacture this. PARAXIAL OPTICS

Spectacle correction of sight is designed only to eliminate defocus errors and astigmatism. These are the only optical aberrations that can be handled by the simplest theory of imaging, known as paraxial optics, which excludes all light rays finitely distant from a central ra y or power axis. Ignoring the majority of rays entering the pupil, paraxial optics examines only a narrow thread-like region surrounding the power axis. The shape of any smoothly rounded surface wi thin this narrow region is always circular in cross-section. Thus from the

paraxial viewpoint, surface shape is toric at most: only its radius may vary with meridional angle. As a toric optical surface has sufficient flexibility to null defocus and astigmatism, only paraxial optics is needed to specify corrective lenses for normal eyes. Paraxjal optics is used in keratometers and

two-dimensional topographic machines. RAYTRACE OR GEOMETRIC OPTICS

The initial objective of refractive surgery was to build the necessary paraxial correction into the cornea. When o utcomes are less than perfect, it is not just

because defoc us correction is in adequate . Typica lly, other aberrations (astigmatism, spherical aberration, coma, etc.) are introd uced by the surgery. These may be cau sed by d ecentered ablation, asy mmetr ic healin g, biomechan ical response, poor s urgical planning, and inadequate or 24 misinformation. To assess the aberrations in the retinal image all the light rays

Orbscatl

Fig . 1: Orbscan

Incident

Reflected

Fig. 2: Specular reflection. This is used in keratometers . This is angle dependent

25

InstantClillical Diagllosis in Oplttl/almologtJ (Refractive SlIIgenJ)

entering the pupil must properly be taken in acco unt using ray trace (or geometric) optics. Paraxial optics and its hypothetical toric surfaces must be abandoned as inadequate, w hich e linunates the need to measure surface

curvature. Ray trace optics does not require surface curvature, but depends on elevation and especially surface slope. The Orbscan uses ray trace or geometric optics.

ELEVATION Orbscan measure elevation, which is not possible in o ther topographic machines. Elevation is especially important because it is the only complete scalar measure of surface shape. Both slope and curvature can be mathematically derived fro m a single elevation map, but the converse is not necessarily true. As both slope and curvature have different values in different directions, neither can be completely represented by a Single map of the surface. Thus, when characterizing the surface of non-spherical test objects used to verify instrument accuracy, elevation is always the gold standard. Curva ture maps in corneal topog raphy (usually misnamed as power or dioptric maps) only display curvature measured in radial d irections from the map center. Such a presentation is not shift-invariant, which means its values and topograph y change as the center of the map is shifted. In contrast, elevation is shift-invariant. An object shifted with respect to the map center is just shifted in its elevation map. In a meridional curvature view it is also described. lbis makes e levation maps more intuitively understood, making diagnosis easier. To sumn1arize: 1. Curva ture is not relevant in ray trace optics.

2. Elevation is complete and can be used to derive surface curvature and slope. 3. Elevation is the standard measure of surface shape. 4. Elevatio n is easy to understand . The problem we face is that there is a cost in converting elevation to curvature

(or slope) and vice ve rsa. To go from elevation to curvature requires mathematical differentiation, which accentuates the high spatial frequency components of the elevation function. As a result, random measurement error

or noise in an elevation measurement is Significantly multiplied in the curvature resul t. The inverse o pe rationr mathematical integration used to convert curvature to elevation, accentuates low-frequency error. The Orbscan helps in

good mathematical integration. This makes it easy for the ophthalmologist to understand as the machine does all the conversion.

ORBSCANlANDII Previously, Orbscan I was used. This had only slit scan topographic system. Then the placido disc was added in Orbscan I. Hence, Orbscan II came into the 26 picture.

Orbscan

Incident

Scattered

Fig. 3: Back-scatter reflection. This is used in orbscan . This is omni-directional

\+- --1

Triangulate an edge point in camera object space (x, y, z) by mathematically intersecting the diffuse renected camera edge ray with the calibrated slit-beam surface.

Fig. 4: Direct triangulation

27

]IIstall tClillical Diagnosis ill Ophth almol0:5'J (Refractive Surgery) SPECULAR VS BACK-SCA TIERED REFLECTION

The keratometer eliminates the anterior curvature of the pre-corneal tear film. It is an estimate because the keratometer only acquires da ta w ithin a narrow 3 mm d iameter annulus. It measures the anterior tear-film because it is based on specular reflection, which occurs primarily at the air-tear in te rface. As the keratometer has very limited data coverage, abnormal corneas can produce misleading or incorrect results. Orbscan can calculate a variety of different surface curvatures, and on a typical eye, these are all different. Only on a properly aUgned and perfectly spherica l surface are the various curvatures equal. The ta bulated SimK values (magnitu des and associated meridians) are the only ones designed to give keratome ter- like measurements. Therefore, it only makes sense to compare kera tometry reading with SimK values. Orbscan uses slit-beams and back-scattered light to triangulate surface shape. The derived mathematical surface is then ray traced using a basic keratometer model to produce simulated keratometer (SimK) values. So it is the difficulty of calculating curvature from triangulated data, the repeatability of Orbscan I Si mK values is usually not as good as a clinica l keratometer. But when several readings of the same eye are averaged, no d iscernable systematic error is found.

So if one reading is taken and a comparison is made, the d ifference may be significant enough to make you believe the instrument is not working properly. So when the placido illuminator was added to Orbscan 11 to increase its anterior curvature accuracy, it also provided refl ected data similar to that obtained with a keratometer. This reflective da ta is now used in SimK analyses, resulting in repeatabilities similar to kera tometers and other placido based corneal topography instruments. Keratometry measures the tear-film, while slit-scan tr ian gu lation as embodied in Orbscan sees through the tear- film and measures the corneal surface directly. Thus, an abnormal tear film can produce significant differences in kerato metry but not in Orbscan II. Curva ture measures the geometric bending of a surface, and its natural uni t is reciprocal length, like inverse millinleters (l / mm). When keratometry was invented this wuamiliar Wlit was replaced by a d ioptric interpretation, making kera tometry values equi valen t on average (i.e. over the original population) to the paraxial back-vertex power of the cornea . As it has become increasulgly more important to distingu ish optical from geometric properties, it is now more p roper to evaluate keratometry Ul "keratometric di opters". The keratometric d iopter is strictly defined as a geometric unit of curvatu re with no optical significance. One inverse millimeter equals to 337.5 keratometric d iopters. 28

Orbscmt

Fig. 5: Beam and camera calibration in the orbscan

Fig. 6 : Ocular surface slicing by the orbscan slit

cornea reflex cornea reflex lens Limbus

Anterior iris

Fig. 7: Detai led orbscan examinat ion

29

Instant Clinical Diagnosis in OplttltalmologtJ (Refractive Surgery) IMAGING IN THE ORBSCAN

In the Orbscan, the calibrated slit, wh ich fa ll s on the cornea, gives a

topographical information, which is caprured and analyzed by the video carnera. Both slit beam surfa ces are determined in camera object space. Object space luminance is determined for each pixel va lue and framegrabber setting. Forty Slit images a re acquired in two 0.7-second periods. During acq uisition, involuntary sacca des typically move the eye by 50 microns. Eye movement is measured from anterior reflections of stationary slit beam and other light sources. Eye tracking data permits saccadic movements to be subtracted form the final topographic surface. Each of the 40 slit images triangulates one s]jce of ocular surface. Before an interpolating surface is constructed, each slice is regis tered in accordance with measured eye movement. Distance betw"een data

slices averages 250 microns in the coarse scan mode (40 slits limbus to limbus). So Orbscan exam consists of a set of mathematical topograph ic surfaces (x, y), for the anterior and posteriGf cornea, anterior iris and lens and backscattering

coefficient of layers between the topographic surfaces (and over the pupil). MAP COLORS CONVENTIONS

Color contour maps ha ve become a standard method for displaying 2-D data in corneal and an terior segment topogra phy. Although there are no wuversally standardized colors, the spectral mrection (from blue to red) is always orgm1ized in definite and intuiti ve way. Blue = low, level, flat, deep, thick, or aberrated. Red = high, steep, sharp, shallow, thin, or focused. ANALYSIS OF THE NORMAL EYE BY THE ORBSCAN MAP

The general quad map in the Orbscan of a normal eye shows 4 pictures. 111e upper left is the anterior float, which is the topography of the an terior surface of the cornea. The upper right shows the posterior float, wluch is the topography of the posterior surface of the cornea. The lower left map shows the keratometric pattern and the lower right map shows the pachymetry (thickness of the cornea). The Orbscan is a three-din1ensional slit scan topographic machine. If we were doing topography with a machine, which does not have slit scan imaging facility, we would not be able to see the topography of the posterior surface of the cornea. Now, if the patient had an abnormality in the posterior surface of the cornea, for example, as in primary posterior corneal elevation this would not be diagnosed. Then if we perform Lasik on such a patient we would create an iatrogenic keratectasia. The Orbscan helps us to detect the abnormalities on the posterio r surface of the cornea. Anothe r facility, wluch we can move onto once we have the general quad map, is to put on the normal band scale fil ter. If we are in suspici on of any abnormali ty in the general quad map then we put on the normal band scale filter. This highlights the abnormal areas in the cornea in orange to red colors. 30 The normal areas are all shown in green. This is very helpful in generalized screening in pre-operative examination of a Lasik patient.

Orbsca1l

OR8SCAN

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31

Instant Clinical Diagnos;s in OplrtlralmologtJ (Refractive Surgery) CLINICAL APPLICATIONS

Let us now understand this better in a case of a primary posterior corneal elevation. If we see the General quad map of a primary posterior corneal elevation we wi ll see the upper left map is normal. The upper right map shows abnormality highlighted in red. This indicates the abnormality in the posterior surface of th e cornea. The lower left ke ratometric map is normal and if w e see

the lower right map, which is the pachymetry map one will see slightly, thin cornea of 505 microns but still one calU10t diagnose the primary posterior corneal elevation only from this readi ng. Thus, we can understand that if not for the upper right map, which denotes the posterior surface of the cornea, one would miss this condition. The Orbscan can only diagnose this. Now, we can p ut on the normal band scale fil ter on and this will highlight the abnormal a reas in red. Notice in Figure 12 the upper right m ap shows a lot of abnorma li ty denoting the primary posterior corneal elevation . One can also take the three-dimensional map of the posterior surface of the cornea and notice the a lTIOlUlt of elevation in res pect to the normal reference sphere shown

as a black grid. In a case of a kera toconus all four maps show an abnormality, which confirms the diagnosis. If we take a Lasik patients topograph y we can compare the pre- and the post- Lasik. This helps to understand the pattern and amount of ablation done on the cornea . The picture on the upper right is the p re-operative topographic picture and the one on the lower right is the post-Lasik pictu re. The main picture on the left shows the difference between the pre- and post-Lasik topographic patterns. One can detect from this any decen tered ablations or any other complication of Lasik surgery. Corneal topography is extremely importan t in cataract surgery. The smalier

the size of the incision lesser the astig1l1atism and earlier stability of the astigmatism will OCCllr. One can reduce the ashgmatisnl or increase the astigmatism of a patien t afte r cataract surgery. The simple rule to follow is that-wherever you

make an incision that area will fiat ten alld wherever you apply sutures that area wili steepen. One can use the Orbscan to analyze the topography before an d after ca taract surgery. For instance in an Extracapsular cata ract extraction one can

check to see w here the astigmatism is most and remove those sutures. In a phaco the astigm atism will be less and in Phakon.it where the incision is sub 1.5 mm the as tigmatism will be the least. We can use the Orbscan to determine the anterior chamber depth and also analyze where one should place the incision when one is performing astigmatic keratotomy. The Orbscan can also help in a good fit of the contact lens with a fluoresce in pattern. SUMMARY

The Orbscan h as changed the wor ld of top ograph y as it gives us an understand ing of a slit scan three-dimensional picture. One can use this in 32 lmderstanding variolls conditions.

Orbscall DrAg-.1 Agarwal Eye Hospital CtMm-'

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33

Instant Clinical Diagnosis ill Ophth alm ology (Refractive S/lrgery) P . Mah",lekshmi 00071 6 CD· 813.'02, 11 :" 5:4 1 AM

ORBseAN

Fig. 12: Three dimensional map of primary posterior corneal elevation. This shows a marked elevation in respect to a normal reference sphere highlighted as a black grid. Notice the red color protrusion on the black grid. This pictu re is' of the posterior sur1ace of the cornea

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34

Orbscan

OABSCAN Differen ce - Anterior Elevati on 0.080 0.070 0 .060 0.050 0.040 0.030 0 .020

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Fig . 15: Pre- and postoperat ive photos of a Phakon it with a Thinoptx ro llable IOL

35

5 Photo refractive Keratectomy with Mitomycin C for High Myopia Belquiz A Nassaralla, Joao J Nassaralla Jr (Brazil)

INTRODUCTION

Excimer laser photorefractive keratectomy (PRJ_.-_

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Fig. 3 C: Corneal topography map (8 and L Orbscn) of the same eye as in Figs 3A and B demonstrating a high irregular astigmatism (-13.6 x 26°) and excessive corneal flatten ing, '1 years after AK plus AK

ORBSCAN

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Fig. 3 0 : Corneal topography map (8 and L Orbscan) of the same eye as in Figs 3A and C shows a progression in the irregular astigmatism (-14 .2 x 171 ") and central corneal flattening, 17 years afte r RK plus AK

68

PlIO to refractive Keratectomy for Residllal Myopia

Fi g. 4 A : SIiHamp photograph of the right eye of a 45 -year-old woman who underwent an Bcui RK in 1990, for moderate myopia (-5.25 -1.50 x 90°). She was undercorrected (-1.75 0. 75 x 165°) and underwent PRK with a sing le topical application of MMC 0.02 % for 2 minutes, in 2003 . No corneal haze was noted during follow-up

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ORBSCAN

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Fig . 4 B : Corneal topography map (8 and L Orbscan) of the same eye as in Fig. 4A, 18 years after RK and 5 years after PRKlMMC. Note the well centered central applanation and the satisfactory postoperative K values

69

10 Recent Advances in Photo refractive Keratectomy C Banu Casar (Turkey)

INTRODUCTION

Photorefractive keratectomy (PRK) was first successfully applied ina n ormally sighted eye by Mc Donald in 1988. The use ofPRK as a main stream refractive modality declined during the late 1990s and early 21st century due to the dramatic increase in laser il1-situ keratomileusis (LASIK). However, there has been a resurgence of interest in the PRK procedure, especially because of the increased number of post-LASTK ectasia cases. In this chapter, recent advances in PRK such as mitomycin C (MMC) and ascorbic acid use, customized PRK (wavefront-guided, topography-guided, and Q factor cu stomized), PRK with solid state lasers and presbyopia treahnent with PRK are discussed. PRKWITH MMC Haze after PRK

H aze is characterized by subepithelial fibrosis caused by an abnormal wound healing response, confirmed by hi stologic studies that show epithelial hyperplasia, disruption of Bowman 's layer, presence of newly formed type III disorganised collagen, vacuoliza tion of keratocytes and abnormal activation of fibrocytes. Although common, the definite etiology of corneal h aze remains obscure. It has been postulated that apop tosis occurs in keratocytes immediately after PRK, w hen the activated migrating keratocytes from the remaining strOlna

produce increased amounts of disorganized collagen and cellular n1atrix, severely red ucing corneal tran sparenc y. It has been suggested, but not conclusjvely confirmed, that the development of postoperative corneal haze after PRK is associated with the removal of the epithelial basement membrane. There are likely many factors related to haze formation. These may include the depth of ablation, the smoothness of the stromal surface, and the time required for the closure of the epithelial defec t. The current genera tion of excimer lasers are characterized by sn100ther ablation profiles and reduced treatment times, 70 which may be associated with reduced risk of haze formation.

Recent Advances in Photo refractive Keratectomy

Hyperbola

Fig. 1: A conic section is the inte rsection of a plane with a cone . By changin g the angl e and location of intersection , a circle , ellipse, parabola , or hyperbola can be produced

71

Illstallt Cliu ical Diagnosis in Opllthalmo[0iJ'J (R efra ctive SlIrgenJ)

Clinically insignificant corneal haze is present in most eyes tha t h ave PRK and may last fo r 1 to 2 years after su rge ry. Clinicall y significant haze onl y occurs in a small percentage of eyes, usually less than 0.5 to 3%, d epending on the level of correction and other factors. Two types of haze are observed alte r PRK. The more common type of ha ze is the typical tra nsitory haze that is noted between 1 and 3 months after surgery. Th is type of haze is rarely associated w ith clinical symptoms and usuall y disappears within the first year after the surgery. The other type of haze (late haze) is much less conunon and is usually noted between 2 and 5 months after the procedure in an eye that has otherwise had a normal outcome after surgery. Late haze may severely compromise vision due to a marked decrease in transparency and regression of the refrac ti ve correctio n. Late ha ze, along wi th

the refracti ve regression associated with it, also resolves over time. Late haze usually persists longer than the more com mon type of earl y haze and in some cases may take more than 3 years to reso lve. Disappearance of haze is associated

with disappearance of myofibrob lasts and remodeling 01 disorga nized stromal collagen. Mitomycin C use as Prophylaxis and Treatment for Haze

Mitomycin C, a potent antiproliferative agent with alkylaling properties, inhibit the proliferation of fibrobl asts and kera tocytes. Mitomycin C inhibits DNA synthesiS, prelerentially affecting rapid ly dividing cells, is fast-acting, and induces long-lasting suppression of ke ra tocyte activity afte r a single dose. Mitomycin C is used prophylactically with PRJ< to prevent haze. MMC is also effecti ve for the treatment of haze after a previous PRK.1n this situation, the epithelium is d ebrided an d MMC is applied with out laser ablation. For the prophylaxiS of haze; MMC is used with: • Primary PRJ0 -0. 22

>1 1 O<e : ,:. ,

D!ssectlon _ ___ ~ ... ".. ;:-. _._ ..-.. : . _. __ : .• : .. _. . _ in lasik

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Fig. 1: The red arrow indicates the plane of cleavage for EpiLASIK

Fig. 2: Moria Epi K

111

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) HISTOLOGICAL FINDINGS

Transmission electron microscopy of the ha rvested epithelial sheets showed minimal evidence of trauma in the basal epithelial cells, the intracellular organelles and intercellular desmosomal connections as well as the hemidesmosomal connections w ith the basement membrane appeared closer to normal with only focal disruptions. Alcohol assisted epithelial separations take place within the basement membrane affecting its integri ty. The intact basement membrane has been found to be important to control the fibro tic activation of keratocytes and faster epithelial wo und healing. To this end, Epilasik with the clean cleavage at the level of basement membrane faired better over LASEK. PRINCIPLE OF EPILASIK

A blw1t epikerotome moves on the eye providing a clean cleavage between the basement membrane and Bowman's layer, lifting an epithelial sheet of 50 - 60~ followed by surface laser ablation requisite for the refractive error. Procedure

leepacks need to be placed on either eye for 15 minutes prior to the procedure. This preoperative step contributes significantly in lessening the pain component following the surgery. The operative eye is prepared w ith three drops of topical propacaine hydrochloride (applied every 5 minutes before the procedure) and povidone iodine and is covered w ith a sterile drape. The epikeratome unit needs to be checked for all its parameters including vacuum build u p and a trial run prior to the procedure. The cornea could be marked wi th the usual markers as in all corneal refractive procedures for a proper flap alignment. Different epikeratomes are presently available in the market. The popular epikeratomes are the Amadeus, Moria, Centurion and Nidek. The Amadeus epikeratome allows a consistent flap diame ter 01 9.0mm, variable hinge width of 1.0, 1.1 and 1.2 mm, 11,000 rpm with an ad vance rate of 3-5 nun /sec and a vacu um build up of 21.5 inch/ Hg The epikeratomes include a blunt plasti c separator instead of the blade in the LASIK microkeratome which have different angles of entry and slide along a path 01 least resistance. A speculum is placed on the eye and copiously irriga ted with chilled BSS or saline. Anesthetic drops are reapplied. The epikeratome assembly is placed on the eye and the vacuum built up. Following adequate vacuum build up Signal and cross check with applanation tonometer, the epikeratome is rW1 on its trac k by pressing on the foot peda l. The assis tant should continuously irrigate with chilled BSS throughout the forwa rd and reverse reill. This crucial 112

EpiLASIK with Mitomycin C

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Fig. 3: Amadeus Epi keratome holders and separators

Fig. 4: Copious ch illed BSS irrigating the track during Epi keratome run

113

Instant Clinical Diagnosis in Opl1tl1alll1olol5l} (Refractive SlIrgen})

measure sign ificantl y a lleviates pain in the postoperative p e ri od. The microkeratome pushes the thin epithelial sheet creating a nasal h inged flap. The epikera tom e is lifted off the eye and the thin flap gently n udged to the periphery. The laser pa rameters fed in the laser machine for the requisite correction is activated, the usual preca utions for centered treatment applied and the surface ablation is performed. After laser ablation, mitomycin C a t 0.02% concentration is applied w ith a merocoel sponge for a duration of 12 sec. The concentration of 0.02% is arrived by a simple dilution measure. 2 mg of mitomycin is mixed w ith 5 ml of sterile water. 2.5 ml of this reconstituted mixture is discarded. The rema ining 2.5 ml is fur ther dilu ted with 2.5 ml of sterile wa ter. From this final reconstituted 5 ml soluti on, 1 ml is taken in a syringe to wet the merocoel which is p laced on the stromal bed. Different exposure times is suggested by different surgeons but a la rge r consensus fa vors 0.02% nlitomycin concentration. Application of mitomycin has been accep ted to significantl y reta rd the cytokine induced in flammatory cascade in the tear film . The exposed surface is then copiously w ashed to remove any remnant of mitomycin. A blunt cannula is then used to gently reposit the thin rolled up epithelial flap opposed to the nasa l hinge. The epithelium is found to extend beyond the epithelial gutter because of the mechanical stretch induced by the cut. The periphery of the flap should be stroked smoothly to remove all the fold s. The epithelial flap shou ld be given adeq ua te time to settle on the underlying stroma. A bandage con tact lens (preferably 8.6 - 8.7 mm diameter) is gentl y placed on the eye and aga in given sufficient time to settle on the flap gently nu dgin g the air bubble awa y under the BCL. The speculum is removed once the flap integrity is checked and BCL is left in place. INTRAOPERATIVE COURSE

The sequence of events may not be smooth in all situa tions. The fl ap may get torn or a buttonhole ma y present. Attempts to salvage the flap, if fail ed, allows remova l of the flap in toto and gently scraping any epithelial tags. Remo val of this thin flap is no quanda ry as in a Lasik fl ap. Su rgeons at different centres have studied the results w ith and w ithou t the flap and the final visual outcome is comparable. Rarely, a stromal incursion could occur (as low as 1% incidence) because of high vacuum and the procedure needs to be aborted. POSTOPERATIVE TREATMENT

As re-epithelialization progresses, the separa ted epithelial sheet shrinks in the central part and has a hazy appearance. 114


Fig. 5: The thin epithelial flap is nudged to the nasal periphe ry

Fig. 6: Merocoel sponge soaked with mitomycin placed on the stromal bed

115

Installt Clinical Diagnosis ill Ophthalmol0:5'J (R efractive Surgery)

The presence of the epithelial fla p itself is lmderstood to ac t as a bandage contact lens preventing the marked in flammator y cascad e of cytokine production. However the epithelium tend s to die out with the new epithelium migrating in from the periphery rep lacing the separated epithelial sheet. Significant epithelial haze is seen in the first 3 days tiLl a newly synthesized transparent epithelial sheet is laid d own. The time of epithelial healing ranges from 3 to 5 days. The patient is started off on a postoperative regime of frequent topical steroids coupled with fourth generation fluoroquinolones for the first couple of weeks. The topical steroids a re gradually tapered off over the 6 weeks. Presence of a mild subepithelial haze may warrant continuation of s teroid drops upto 3 months w ith comp lete clearing of the haze. Artificial tear substitutes are maintained for 6 weeks or longer. The bandage contact lens is removed after 5 da ys by which time th e epithelial healing is complete. Mild analgesics are indicated for 3-5 days. Different studies favo r the usage of vitamin c (500 mg - BD dosage) over the 6 weeks period. Clinical Deductions

The present generations ofepikeratomes are very safe involving intact epithelial flaps. The 60 ~ thin flap expand the range of correc tion leaving significant residual stroma l bed. However, as of, now, mild to moderate myopes do perform favourably w ith epi procedures. The visual outcome is comparable to Lasik after the initialS days. The wow effect of Lasik, however, is missing. The superficial lamellar fibres show a more predictable biomechanical response then in the thicker flaps . Wavefront ablation performs better as the flap induced aberra tions of a thick Lasik flap are obviated. The initial corneal thickness of 480 - 500 ~ and the residual bed of 300 + ~ is a safe limit as of today. CONCLUSION

TIle armamentarium of refractive surgery, at the present day scenario, provides varying options for differing corneal parameters. The final onus falls on the

surgeon to a nalyse the preset criteria and adopt a rational approach providing the requisite customized treatment with optimal visual outcome. The future awaits for a customized biomechanical wound response to be tailored to our h'eahnent stra tegy.

116


Fig. 7: Bandage CL placed on the reposited epithelium

Fig. 8: Damaged epithelial flap could be discarded

Fig. 9: As reepithelia lization progresses, the separated epithelial sheet shrinks in the central pa rt and has a hazy appearance

117

15 One-shot Epithelium-rhexis: Personal Technique Roberto Pinelli (Italy)

INTRODUCTION

The surface ablation technique through excimer laser is a procedure in use since long time. In the last 25 years this technique has h ad an evolution and many surgeons in the world gave their contribute to develop different sub-techniques of surface ablation. The most important issue is to remove regularly the epithelium and obtain a smooth surface in order to perform excimer laser in a safe and effective way. Questions

1. H ow to remove the epithelium in order to obtain a regular surface and perform the excimer laser and obtain a pure abla tion without central islands or irregularity? 2. H ow to manage the post-operative phase? 3. Is the post-operative pain rela ted to the removal of the epithelium? 4. The re-epithelialization depends on the technique? At the beginning of this procedure, the most common technique was to remove the epithelium ll1echanically with surgical instruments: different spatulas to remove the epithelium were designed b y a lot of surgeons but the problem of the technique is the timing of this maneuver and the elegance of this delicate part of the surgery. Alcoholic solution is another technique which is able to separate the epithelium from the Bowman' s melnbrane and consequently to relTIOVe it more easily. Once that the epithelium is treated with the alcoholic solution, the problem is how to remove it: aga in it is possible to remove it with more soft instruments, not necessarily surgicaL EDiLASIK and LASEK are two techniques able to remove the epithelium and then, after the ablation, to put the epithelium again in its natural position. Description

In our experience at Istituto Laser Microchirurgia Oculare, Brescia (Italy), surface ablation is around 10% of the procedure, being the 90% of our corneal procedure 118 the thin-flap LASIK.

One-shot Epithelium-rhexis: Personal Technique

Fig. 1: The metal ring surgical instrument is applied on the cornea

Fig . 2: The alcoholic solution is adm inistered on the cornea with a metal ring surgical instrument

119

Instant Clinical Diagnosis in Ophthalm ologtJ (Refractive Surgery)

Our favourite approach to surface ablation, called "Epithelium-rhexis ASA" (Advanced Surface Ablation) is to remove the epithelium with a maneuver that we call "epithelium - rhexis". This technique is very similar to the Capsulorhexis Technique in the cataract surgery. As you can see in the images we usually use a dry merocel after 25 seconds application of alcohol solution on the epithelium and we detach epithelium with one circular induced maneuver in order to have only one single approach to the epithelium and less trauma. If we are able to remove the epithelium circularly in one n1aneuver we will have not only less problems but even an optical zone around 8 mm read y to the ablation with a perfect smooth surface. The epithelium detachment from Bowman's membrane is very crucial in this technique; after the alcohol solution treatment the epithelium is more soft and once broken the epithelium membrane with the merocel we can choose a clockwise movement or an anticlockw ise movement (it depends on the surgeon's attitude), and in one circular shot we can remove the epithelium at 8 mm optical zone. As you can see by the figures and in the CD-rom the maneuver is relatively simple and clean. An interesting question can be: why we remove the epithelium at 8 mm optical zone and we do not go to the limbus? In our experience we compared one eye (8 mm optical zone disepithelialization treated) with another (10 mm optical zone of disepithelialization) and as far as transparency of the cornea, visual acuity post laser excimer and absence of haze is concerned, we can observe that the refractive result was in the two eyes very similar. The eye treated with 8 mm optical zone epithelium-rhexis was significantly better as far as less pain for the patient and more fast re-epithalialization: 3 days only compared to the 5 days of the collateral eye with the disepithelialization at 10 mm optical zone. We think that touching the cornea with the merocel and not with a surgical instruments we cause less trauma to the epithelium : less surgery in the classic meaning of the word is giving to the eye less microtraumas and consequently less complain as far as pain is concerned. The proced ure to epithelium-rhexis and the surface ablation is in our Institute always bilateral and in topical anesthesia. To perform a correct epithelium-rhexis very important are: • the quality of the alcoholic solution; • the timing of preparing the solution; • the concentration of alcohol in the solution (with BSS - balanced salt 120 solution, we use 20% solution of alcohol).


Fig. 3: The epithelium-rhexis is performed with mera-cell in an anti-clockwise movement

Fig . 4 : "One -shot" epithelium-rhexis is totally performed

121

Instant Clillical Diagnosis ill OplttlwlmologtJ (Refractive SlIrgery)

The patient is prepared before with three drops of Propacaine and three drops of Tetracaine in each eye at the fo llowing intervals of time: • 10 minutes before surgery • 5 minutes before surgery • some seconds before the surgery. The alcoholic solution is administered on the cornea with a metal ring (E. Janach sri, Como -Italy), a surgical instrument, actually very easy to find in the surgical instruments market. After we drape the eye lashes (the upper and not the lower eyelashes). After the classical bilateral epithelium-rhexis ASA ( in the CD-rom you can see all the maneuvers) we put in the eye some drops of Oftacilox (SA AlconCouvreur NV- 2870 Puurs - Belgium) and then the soft contact lens. After the excimer laser abla tion, a soft con tact lens is enough to protect the ablation, and contact lenses after a bilateral treatment are removed usually on day 4th postoperatively. Second eye is performed immediately after the first eye just operated. Finally we cl,eck the both operated eyes at the slit lamp in the consultation room in order to be sure that the con tact lenses are in the proper position. When the patient will come back to the Institute, on day 4th postoperatively, we remove the two contact lenses, and we check the complete re-epitilelialization of the cornea. After a learning course, which can be different from surgeon to surgeon, usually no t more than 10 hours, this teclulique can be easily performed by every refractive surgeon.

It is easy, simple and well accepted by tile patients.

lil the last five years of use of this teclmique no haze was detected in our patient, no problems of re-epithelialization and no central is lands were observed on the surface of the cornea and the new epithelium was extremely reg ular. Also the satisfac tion questionnaire of the patient reported as high satisfaction level very close to LASIK procedure. So the patients are accepting this teclmique of Advance in Surface Ablation with grea t confidence. We started to perform this techniq ue five years ago beca use the classical mecha nical epithelial removal was not well accepted by the patients although the v isua l acuity postoperative was extremely positi ve: th e satisfaction question naire of th is patient by th e classical surface ab la ti on w ithout epithelium-rhexis was very different from the satisfaction questiolU1aire of

122

LASIK procedure; now the sati sfaction questionnaires of LASIK procedure


Fig. 5: Afte r the laser ablation , a contact lens is applied

Fig. 6: Specu lum removed. At this point the surgery is over

123

Instant C/ittical Diagttosis in OphthalnwlogtJ (Refractive Surgery)

and of Advanced in Surface Ablation Technique through epithelium-rhexis are very close. In our Institute the popularity of this surface technique is very high and also the patient' s reaction to it: when we decide for this technique, generally due to the pachymetry < 500 microns (which is the limit of our thin flap LASIK and our Advances in surface Ablation Teclmique) results are very positive. Patient selection of one-shot-epithelium-rhexis compare to the LASIK thin flap technique is substantially focused on the visual defect and the pachymetry: • If the pachymetry is < 500 microns we decide for Advanced in Surface Ablation Technique; • If the visual defect is from - 0.5 to -60 of myopia, with or without as ti gm atism and from + 0.5 to + 3 of h yperopia, w ith or without astigmatism, as far as myopic population, and we have> 500 microns we switch to thin flap LASIK Technique; • In hyperopia also, when we have central pachymetry of > 500 microns, we switch to thin flap LASIK Teclmique. • Phakik IOL' s also, and their implantations, are covering the population ACO with higher visual defects in presence of an anterior chamber (minimum3mm). "Epithelium-Rhexis ASA " Technique Different phases: 1.

T he patient is prepared before with three drops of Propacaine and three drops of

Tetracaine in each eye at the following intervals of time: 10 minutes before surgery • 5 minutes before surgery ~

2.

some seconds before surgery Alcohol solution is administrated on the cornea

3.

Upper eyelashes are draped

4. 5.

7.

Epithelium is removed with one circular maneuver by using a dry merocel Excimer laser ablation is pertormed Some drops of Oftacilox are administered in the eye and then a soft contact lens is inserted Both operated eyes are checked at the slit lamp

8.

On 4th day postoperatively the contact tenses are removed

6.

124

One-shot Epithelillm-rhex is: Personal Technique CONCLUSION

We will see in the next years what will be the destiny of the surface ablation bein g thinner and thiJuler the flap of the LASIK and growing the implantation of Phakik IOL. But we think that the surface abla tion with soft and nice epithelium-rhexis ASA technique is reducing the pain and giving to the eyes of our patients bri ll iant and visual acuity and the regular absence of hazes still remains an issue and an option for OU f patients. In the CD-rom you can see all the maneuvers of this technique, from the begiJUling of the surgery to the end and in the box you will see a summary of the most important phases in order to pe rform a correct epithelium-rhexis in one shot and in order to obtain a perfect advanced disablation.

125

16 Surface Ablation after laser In Situ Keratomileusis; Retreatment on the Flap Jeroen JG Beerthuizen (Netherland)

The most common complication of laser il1 situ keratomileusis (LASTK) is postoperative overcorrection or undercorrection. Such residual ametropia can be bothersome to a patient and laser re trea tment can be considered. There are

different ways to retreat a post-LASIK cornea. The flap can be relifted, even years after the original LASIK p rocedure, although this might be challenging at times. It is also possible to recut a new flap, although this is less safe and effective than a relift. In both p rocedures, the underlying stromal bed is being treated and the amount of residual stroma should be sufficient to p revent ectasia. Disadvantages regardin g safety include an increased chance of epithelial ingrowth after a relift and the risk for diffuse lamellar keratitis and flap striae. To avoid problems with residual stromal thickness, ablation can also be p erformed on the tmdersid e of the fla p or on the surface of the flap. Surface ablation options include intra-epithelial or subepithelial photorefractive keratectomy (PRK) and laser-assis ted subepithelial keratectomy (LASEK). Subepithelial PRK j LASEK w ill be discussed in this chapter. Surface ablation has additional adva ntages. Superficial abnormalities such as map-dot-fingerprint lesion s are likely to benefit from a superficial approach. Microstriae in the flap tend to smooth en out after surface ablation, whichrnight improve quality of vision. Patients in need of a hyperopic retreatment 'with a small flap can be treated without the need of recutting a larger flap. FLUthermore, wavefront-guided treatment of flap-induced higher-order aberrations is more

logical when the flap is left in place. Finally, patients with a history of postLASIK dry-eye syndrome are better off wi thou t a relift. The biggest disadvantage of surface ablation retreatment is the chance of developing haze. Carones et al found severe haze in 14 of 17 eyes after PRK retreatment for regressed myopic LASIK. The average amount of corrected myopia in tha t study was -2.48 ± -0.74 D (range -1.50 to -3.75). 111e wound reaction was much more aggressive than expected and seemed to be related to

126

Swfaee Ablatioll after Laser In Si tu Keratomileusis; Retreatmellt 011 tile Flap

Fig . 1: Severe haze after PRK on the flap

127

Instant Clinica l Diagnosis in Ophthalmology (Refractive Surgery) the lamellar cut. It is hypothesized that app lying laser energy to a stromal area with previously actived keratocytes, which can be found arow1d the flap interface, leads to an exaggerated wound-healing response. This would imply that the combination of flap thickness and amount of ablated flap stroma relates to the chance of developing haze. Problems with severe haze have not been seen after PRK treatrnentof patients with LASIK flap complications and PRK retreatment after complicated LASIK. In more recent studies, good results regarding safety and efficacy were fOW1d for correcting low amounts, less than -1.50 D and -2.00 D respectively, of residual ametropia. Caution should be ta ken with hyperopic corrections. In both studies, no Mitomycin-C (MMC) was used. The use of MMC might be considered in treating higher amounts of residual ametropia if surface ablation is still preferred. TECHNIQUE

The epitheliW11 is trephined with the LASEK flap hinge opposite to the LASIK flap hinge. Application of 20% ethanol for 20 to 30 seconds is advisable to suffiCiently loosen up the epithelium. After rinsing away the ethanol, a LASEK flap can be created by moving epithelium away from the LASIK flap hinge. By moving in that direction, changes of accidentally dislocating the LASIK flap are extremely low . lNhen the epithelium is removed and Bm,vn1an' 5 membrane dried, the appearance of microstriae is very common, also in eyes that did not shm,v microstriae preoperatively at the slitlamp. Laser ablation can be performed

in the usual manner. After the abla tion, the cornea is rinsed with chilled balanced salt solution (BSS) and th e e pithelial flap is either repositioned or removed. A bandage contact lens is placed on the eye. Postoperative medications and follow -up visits are the same as fo r a regular surface ablation .

128

Surface Ablation after Laser III Situ Keratomileusis; Retreatmellt on the Flap

2 12 eyes 12 rno postop

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-2,5 -3 Attempted correction (0 ) Fig. 2 : Attempted versus achieved correction in sur1ace ablation after LASIK

129

17 Wavefront Analysis and its Clinical Significance Yan Wang, Lihua Fang, Boyan Li, Kanxing Zhao (China)

THE CONCEPT OF THE WAVEFRONT ABERRATION

Wavefront aberration, which is originated from Physical Optics, is defined as the difference between the actual aberrated wavefront and the ideal wavefront. It is illustrated in Figure l. METHODS OF DESCRIBING WAVEFRONT ABERRATION

Wavefront map, which can display d istortions in phase on the differe n t positions of the pupil, is considered the most visualized mode to describe the wave aberration of the human eye. This wa y is similar w ith the corneal topography. Wavefront aberration map can be also reconstructed w ith mathematica l fun ctions, such as Taylor polynomia ls, Zernike polynomials and Fourier transform polynomials. 111e comm on use for fitting ,-v ave aberrations is the Zernike p o lynom ial eq uatio n s ince Ze rn ike aberrations have several

advantages. The Zernike polyno mial is a set of basis functi ons and each function has a coefficient the relative va lu e of which corresponds to the an10unt of that particular aberration. In addition, the Zemike polynomials area complete set of polynomials that are orthogona l over a circular pupil, and then the variance is directly given by the sum of the square of the Zernike coefficients. Formally, it has the form k

W( p , B) =

L L" C"'Zm(P, B) 11

11 = 0

Il

m =- II

lI-l ml=I'H'lI

Where the index n is the order of the Zernike polyno mial, m the meridiona l frequency of the sinusoidal component of the Zernike polynomial and k the maximum order of the polynom ial series. The distribution of Zernike terms is shown in Figure 2.

130

Wavefront AI/alysis al/d its C/il/ical Significance

Pupil

Pupi l

•

Idea reference

~""ro~r"\

Wavefront error W(x ,y)

Fig. 1: Wavefront aberration

,

z-6

,

z-4

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z,0

z,'

z,'

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Fig. 2: The distribution of Zernike terms

131

Instant Clinical Diagnosis in Ophtlralmologtj (Refractive Surgery) THE SIGNIFICANCE OF ZERNIKE ABERRATIONS

The Zernike term with n=O is referred to piston (z~ ).It does not induce image distortion. The Zernike terms with n=l are referred to tilts including vertical tilt (Z,-' ) and horizontal tilt (Z: ). They only make the whole wavefront tilt relative to its original position. The Zernike terms w ith n::::2 are referred to second-order aberration . The

central term is defocus ( Z~ ). On either side of it are the astigmatisms including oblique astigmatism (Z - 2) and with-/ against-the-rule astigmatism ( Z 2) . 2

2

The Zernike terms with n::::3 are referred to third-order aberration including vertical coma ( Z;' ), horizontal coma (Z~) , obligue trefoil (Z;3 ) and horizontal trefoil ( The Zernike terms with n=4 are refe rred to fourth-order aberration. The middle one of these is called spherica l aberration (Z~ ) . Spherical aberration is defined as the difference between the focalization of light from the margin of the entrance pupil and that of light from the central portion. The Zernike terms with n=5 are referred to fifth-order aberration. The middle two tenns are defined as second horizontal coma (Z~) and second vertical coma ( Z ; l), respecti ve ly. The other fO llr terms are not specific definition in the classical aberrations.

Z: )

INTERACTION AMONG WAVE ABERRATIONS

I. Interactio" among wave aberratio"s for the complete eye: Mathema tical independence of the Zernike modes does not mean their inopact on visual performance is independent. Acuity varies significantly depending on which modes are mixed and the re lative value of each mode. II. Interaction between cornea and len s for specifiC terms of aberrations: The wavefront aberrations produced by the internal optics (primarily the crystalline lens) offset, or compensate for, the aberrations produced by the cornea to reduce ocula r wavefront aberrations. This effect is illustrated in Figure 3. The spherical aber ration (Z ~) is well compensated regardless of refractive

error. Also horizontal coma (Z~) is found well compensated. Clinical Examples

Figures 4A to C show three wavefront maps of high-order aberrations for the real eyes after refractive surgery. The total RMS in Figures4A to C is l.13, l.03 and 0.91 ,U In, respectively. 111e most components of high-order aberrations are trefoil (A), coma (B), and spherica l aberration (C), with RMS being 0.41, 0.88 and 0.82 ~m, respectively. Figure 5 d emonstrates point spread function (PSF) for the eyes correspond to Figu re 4. 132

Wav efront Ana lysis and its Clinical Significance

+ Cornea

Internal

Tota l

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Trefoil (RMS o0.41 )

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Spherical aberration (RMSoO.82 )

Figs 4A to C: (A) Trefoil (RMS = 0.4 1) Wavefront maps of (S) Coma (RMS = 0.88) highorder aberrations for postoperative (C) Spherical aberration (RMS = 0.82) eyes

Trefoil

Coma

Spherical aberration

Fi g. 5 : PSF for the high-order aberrations of the real eye corresponding to Fig . 4

133

18 Wavefront lASIK Mark Wevifl, Emanuel Rosen (UK)

INTRODUCTION

LASIK has proved effective in reducing refractive errors, but it is known to cause higher order aberrations (HOA's), specifically spherical aberrations and coma. Patients may have reasonable Snellen visual acuity yet may con1plain about debilitating visual synlptoms s lich as nig ht vision disturbances and

ghosting. Therefore, quantifyin g and improving quality of vision after LASIK has become important. Contrast sensitivity testing has been helpful, but more recently wavefront measurements have been used to assess higher order

aberrations (HOAs). The link between HOAs and visual symptoms is the subject of ongiong studies, but spherical abe rra ti ons have been linked to starbursts.

Wavefront-guided ablations can red uce u nwa nted side effects of LASIK especially in low light conditions, red uce enhancement rates, improve the

quality of vision of patients who are dissatisfied with the result of U1eir treatment, reduce fear of LASIK and offer patien ts excellen t vision . The sources of image blur in the human eye are diffract ion, aberrations and scatter. Scatter is relevan t in the ageing eye. Diffra ction is significant w ith

small pupils, is less significant with larger pupi ls, but cannot be eliminated. But aberrations can be modified . The goal o f Wavefron t-guided LASIK (Wg LASIK) is to correct all optical aberra tions o f the eye, which reduce vis ual quality leaving only the spatial resolution of the neuroretina as the lin1iting factor for Optimtffi1 vision . In other words the concept of "supervision" may be achievable. Knowledge and technology are progressing rapidly and there are already a number of benefits of Wg LASIK. ADVANTAGES OF WAVEFRONT GUIDED LASIK

Wg LASIK can be directed to reduce o r eliminate all or certain HOA's and it can be customized to the individ ual eye. Among the benefits are the poten tial to in1prove the quantity of vision (e.g. the Snellen visual acuity), and the quality (e.g. contrast sensitivity). Wg LASIK m ay also reduce post-LASIK n ight-vision problelTIS, w hich are frequently caused by an i.ncrease in aberrations. Stud ies

have shown increases in pre-existing H OA's after standard LASIK, reductions in HOAs after Wg LASIK and studies compa ring standard versus Wg LASIK 134 have shown the benefits of Wg LASIK. H owever there is limited evidence that

W avefrollt LASIK Pre: Wavefront maps: Total aberrations

HOA's

Post:

Total aberrations

HOA's

Fig . 1 (eonld .. .)

135

Instant Clinical Diagnosis in Ophthalmology (Refractive SurgenJ)

136

Wg LASIK consistently outperforms con ventional laser in sit1l keratomileusis that incorporates broad ablation zo nes, smoothing to the periphery, eyetrackers, and other technological refinements. It is evident that wavefrontcustomized ablation holds a promising future and merits ongoing investigation. Figures 1 and 2 illustrate the potential benefits of Wg LASIK (Data courtesy of the Kirkwood-Fyfe Clinic, Aberdeen, Scotland). Preoperatively the patient had low myopia with refractions of -1.5 DS (6 / 6) in the right eye and -2.25 DS (6 / 6) in the left eye. He had Standard LASIK in the right eye with an Alcon Ladarvision 4000 laser. He complained postoperatively of poor vision, which is reflected in the increase higher order aberrations in the postoperative data in Figure 1. Therefore, his left eye treatment was delayed until Wg LASIK (Ladarwave) was available. Three months after treatment of his left eye and a year after treatment of his right eye his refractions were +0.50 / - 0.25 x 44 (6/ 6) in the right eye and 0.00 DS (6/4) in the left eye. His HOAs and point spread function in the left eye were reduced, subjective visual quality and best corrected Snellen acuity had improved, and the patient was happy with the result. This is an isolated case report and does not represent the experience of all Standard or Wg LASIK patients . Studies have shown that HOAs can increase in eyes that have received Wg LASIK, particularly eyes with low amounts of preoperative HOA's. In addition, comparison of the efficacy of different laser platforms has shown differing degrees of improvement, with some showing improvement in all HOA's and others showing improvement only in some HOA's. This may indicate a need to improve the algorithm. Therefore, there are limitations to the effectiveness of standard and Wg LASIK w hich contribute to good or poor outcomes with either procedure. Patients who are dissatisfied with the ou tcome of their LASIK may require repeat surgery to achieve a satisfactory visual outcome. Reoperation rates for primary myopic keratorefractive surgery range from 5.5 to 8.3%. Wavefront technology can measure and trea t optical aberrations that could not be addressed previously with standard refractive surgery and, as such, offers an additional method for enhan cement in patients who had not achieved satisfactory outcome with traditional keratorefractive surgery. A number of studies using different laser platforms and Wg LASIK have claimed better results with wavefront-guided enhancement compared to standard LASIK enhancement. Studies have shown improved efficacy, predictability, and safety, a decrease in aberrations, expanded optical zones and improved subjective symptoms of glare and halos with Wg LASIK. H owever once again there are differences in outcomes with different platforms and a study by Jin showed conventional LASIK retreatment was superior to wavefront-guided LASIK retreatment in both efficacy and safety. Therefore there are limitations that

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137

Instant Clinical Diagnosis in Ophthalmologtj (Refractive Surgery) affect the efficacy of enhancements and further study is required to consistently deliver better results with Wg LASIK compared to standard LASIK. Wavefront data capture is more difficult in highly aberrated eyes. Some post LASIK eyes have significant HONs, and in these eyes topographically guided treatments, or perhaps an initial treatment with th e fluid masking technique may be more beneficial. More study is required to optimize QutcOlnes of these complex treatments.

LIMITATIONS OF WAVEFRONT GUIDED LASIK

To acheive supervision a number of limitations of current wavefront data capture and delivery systems have to be overcome. There are many factors that affect the amount of postoperative aberrations present after Wg LASIK. The flap cut, the flap lift, and the subsequent biomechanical and postoperative healing responses of the cornea, dynamic eye movements that occur during the ablation, constant offset errors of ablation centration and the efficiency of a laser pulse when striking differ,ent areas of the cornea play roles. Inhomogeneities in the cornea, fluctuati'"ons in the laser's intensity, and changes in humidity and other factors affect the ac tual ablation profile applied to the cornea for each individual eye. A study by Buhren and Kohnen showed that the overall change in H OAs using the Zyoptix 3.1 system was a result of simultaneous increases and reductions in HOAs. Various factors determined the net effect. The wavefrontguided algorithm had a strong effect on the reduction of H OAs. Larger pupil diameters reduced the p redictability of HOA reduction. The benefits of the wavefront-guided algorithm were minimised by the induction of spherical aberrations and coma. It follows that the high er the attempted spherical error correction and the smaller the optical zone, the higher the amount of induced spherical aberration and coma is induced. Age, preoperative cylinder and right or left eye did not correlate with induced changes. LASER FACTORS

Laser factors including hot or cold spots in the laser beam, inaccurate registration or tracking can also playa role. Hersch et al developed a mathematical model of the change in asphericity of the cornea when undergoing laser ablation . They concluded that the angle of incidence of the laser beam across the ablation area causes the change in spherical aberration. Therefore changes in laser algorithms are need ed, which deliver more ablation to the 138 peripheral optical zone, preserving the p rolate shape of the cornea. In addition,

Wavefront LASIK Pre: Wavefront maps: Total aberrations

HQA's

Post:

Fig, 2 (eonld ... )

139

Inst ant Clinica l Diagnosis in Ophthalmology (Refractive Surgery) to correct other aberrations w ith wavefron t treatments, fluence variability across

the optical zone has to be considered . BIOMECHANICAL ISSUES

Biomechanical effects of the flap and wavefront-guided laser ablation induce postoperative optical aberrations that are not explained by the ablation profile. These effects are dependant on man y fac tors incuding the type of procedure (surface treatment, femtosecond LASIK or microkeratome LASIK), depth and diameter of ablation and corneal h ysteresis. Corneal hysteresis refers to the integrity and elasticity of the cornea, which is difficult to measure and varies from patient to patient. There are 2 m ain components of the biomechanical response of the cornea to laser refractive surgery, namely structural instability and biomechanical remodelling of the anterior surface. Structural instability or increased distensibilty of the cornea is important in terms of the risk of developing post LASIK ectasia. Ectasia produces a number of higher order aberrations including coma. The biom echanical remodelling produces central fla ttening accompanied by mid peripheral steepening and thickening caused by severing of circumferential tension bearing lamellae. This produces a hyperopic shift and probable spherical aberration. The creation of the LASIK flap alone can modify the eye's optical characteristics in low-order aberrations and HOAs. A significant increase in HOAs was found in Hansatome LASIK patients compared to an IntraLase group. This may have significant clinical implications in wavefront-guided LASIK treatments, which are based on measurements made before flap creation. Better UCYA and manifest refractive outcomes after LASIK with the femtosecond laser compared to the Hansatome have been noted. This may be the result of reduced postoperative astigmatism and trefoil and ma y have clinical significance for wavefront-guided treatments. Therefore the corneal biomechanical response to ablative surgery m ay significantly affect outcomes, and should be taken into account when plalU1ing customized procedures.

ROLE OF THE PUPIL

The pupil plays an important role in the quality of vision after laser refractive surgery. Diffraction through the pupil causes image blur. Also postoperative aberrations can be caused by the static offset of a wavefront-guided ablation due to pupil shift. Shifts in pupil center location can occur between preoperatively aberration measurements of the dilated pupil and when the 140 Wg LASIK is done with an undilated pupil. On some laser platforms wave

Wavefrollt LASIK

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f - - - - - - - - Zoom' 10 "or hlgn Ofdot tonn. r - - - -___--< Jr90%] ca n be trea ted successfully with the Stan dard [Wavefront Optimized] progra 111 . Indications for the Standard or Wavefront Optimized [WFO] Treatment

The WFO treatment is also desc ribed as the Standard Treatment Strictly spoken WFO trea tment is also custom ized treatment because it is adjusted according to the pa tient's refraction as well as the patient's K-readings. Most eyes with no Significant aberrations and normal pupil sizes can be very successfully treated with the Wavefront Op timized [WFO] treatment. Various studies have demonstra ted that the patients treated with the WFO ablation will have better n.ight vision as we ll as better contrast sensitivity than pa tients treated with conventional excimer laser trea tment. Indications for Custom Q Treatment [F-CAT]

Some surgeons will do Custom Q [F-CAT] for all primary eyes, because they 166 believe it is ideal to give every patien t the ad va n tage of maximum asphericity.

Customized Excimer Lase,. Treatment 50

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Fi g . 11 : Sche-matic representati o n of an ablat ion creating an obJate cornea . The red line dep icts the preoperat ive cornea and the black li ne the postoperative ob late cornea

167

Instant Clinical Diagnosis in OplttltalmologtJ (Refractive SurgenJ)

Eyes with large mesopi c pupil s are pron e to have poor nightvision postoperative and can be very successfully treated with the Custom Q program. Custom Q treatment with little or no refractive change is a good option for enhancement treatment in patients with good snellen acuity who still complain of poor vision.

111ese patients may have 1.0 [20/ 20] VA after recent LASlK but are not satisfied with their night vision and / or their contrast sensitivity. After the Custom-Q enhancement treatment, they w ill achieve better contrast sensitivity as well as

better nightvision and they will experience better subjective quality of vision. Indications for T-CAT: These eyes usually cannot be corrected to 20/20 BSCV A pre-operatively because of significa nt lowe r and higher order aberrations of the cornea. The most common and impo rtan t indications in this group include:

Previous penetrating keratoplasty [PKP]. Previous radial keratotomy [RK] Small optical zones after previous LASIK. Decentered optical zones after previous refracti ve surgery. Any irregu lar corneal astigmatism. T-CAT ca n also be used to create asphericity in primary LASIK treatments. T-CAT Following Previous PKP

These eyes can be treated with LASIK or ASA [ad vanced su rface ablation] When there is no contra-indica tion, it is better to do LASIK because of the rapid, pa infree recovery. T-CAT LASlK fo r PKP has a few problems: Firstly it is difficult to obtain good maps, mainl y because the peripheral donor cornea is often so distorted tha t the topolyzer carmot measure the peripheral cornea. This, in turn, reduces the tota l information available to the surgeon and prevents the use of the T-CAT. Secol1dly we have the induced myopia after T-CAT willch has to be anticipated and pre-empted. The patient should be forewarned abou t this myopia and the patient should be expecting a second laser treatmen t 3-6 months after the first treatment to compensate for the induced myopia. Thirdly , some transplanted corneas ha ve a slight haze even if the transplant was otherwise successful, and this will also red uce the fina l visual acuity. T-CATafter Previous RK

These are some of the most difficult eyes to treat w ith T-CAT mainly because it is extremely difficult to get good maps of the peripheral cornea. Reason being 168 that the RK-cuts have so distorted the peripheral cornea that good readings are

Customized Excimer Laser Treatme1lt

Fig . 12: Patient view of tracker and lights

Fig, 13 : Decentered ablation as a result of eye rolling. The patient did not manage to fixate on the fixation light during surgery

169

Illstant Clinical Diagnosis ill Ophthalmolo?;!) (Refractive Surgery)

often impOSSible with the placid o d isc based Topolyzer. 1f good maps are obtained it is easy to treat these eyes. Once again it is mandatory to get good repeata ble maps of the cornea. Once this is done the most impo rtant other problem is to precalculate the induced myopia and to compensa te fo r it. The TNT [Topography Ne utralisa tion Test] is performed to do this. 1f the TNT is successful the patient will have emmetropia post-operative. If not, the eye will be myopic and will require another treatmen t after about 3 months to correct the residual myopia. Indications for Oculink Ablation Based on the Oculyzer

It is very sim ilar to the indications for T-CA T, b ut the Oculyzer should be so much better than the Topolyzer that it should re nder the Topolyzer obsolete. We repeat indications [same as for T-CATI again: Previous PKP Previous RK Sm all optical zones after previous LASIK. Decentered optical zones. Any irregular corneal astigm atism. Indications for A-CAT

The A-CAT is Wavefront guided Lasi k based on the wavefront analyzer data. The ma in advantage of A-CAT is that it will correct for lenticular as well as corneal aberrabons. Off course this w ill have certain disadvantages too, because

len ticular aberrations may change as the patien t becomes older. Another important hmc tion of A-CAT is that it will correct most HOA 's as well as lower order refractive errors. [Obtai ning Maps for custom ablation for d iscussion of HOA's] Correcting of HOA's only gives a small im p rovement of snellen VA because snellen VA is measured at high contrast levels with relatively small pupils. Correcting HOA's has more effect on contrast sensitivity and night v ision than

on snellen acuity. HOA's are usually situated peripherally and only have significant effect on vision at lower levels of illumina tion w hen the pupils are relatively wide. A-CAT is usually indica ted for: Eyes with exceptionally wide p upils. Patients with poor con tras t sensitivity and known poor night vision. Enhancement Lasik for eyes w ith small residual refractive errors. 170 Eyes with known abnorma l amoun ts of higher order aberration.

Customized Excimer Laser Treatment

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Fig. 15: Shows the decentered optical zone after previous RK. Note the poor quality of the superior nasal area of the map. This is quite a common finding in previous RK eyes and is caused by the severe irregularities of the RK incisions

171

Instant Clinical Diagnosis in Ophtlra lmologtJ (Refractive SlIrgenJ)

A-CAT can also be done for primary Lasik, if the surgeon elects to do it. The reason it is not done regularly is that it takes a lot longer than standard wavefront optimized treatment. OBTAINING MAPS FOR CUSTOM ABLATION TREATMENT Measuring Technique

During the measurement of any Topographical or Wavefront map a number of requirements must be met. 1. Good patient cooperation. 2. Pe rfect patient head posi tion and s tabi li ty of the head during measurements. 3. An excellent tear film is important. Artificial tears without preservative

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can be used. Accurate alignment of the eye and visual axis. Management of the position of the brow, nose or other possible obstructing factors. For Wavefront measurements the pupil must be dilated. For Topolyzer it is better to have a small p upil. Peripheral map data is importan t and care should be taken to acquire enough peripheral da ta.

DIFFERENT MAPS Topolyzer Maps

The Topolyzer maps the cornea . It onl y evaluates the cornea and is inherently different from the wavefront maps. Th e Topoly zer uses a placido disc to project placid o rings onto the cornea. 22000 points are sampled on the reflected ring pattern. The Topolyzer measures slope which is converted to height da ta. It combines keratom etric and topographic measuring methods in a single unit. The reflected altered image is captured by a CCD camera and sent to the computer which calculates the topography of the cornea. This produces a topographical map which is shown on the computer screen. Topolyzer data becomes more inaccurate the further peripherally it is measured. In addition, no useful da ta is obtained inside the central placido disc ring projected onto the cornea . The ring projections of the placido disc can be obscured by the nose, brow and eye lashes. To avoid this, the patient's head should be well positioned and 172 the tearfilm must be good.

Customized Excimer Laser Treatment

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Instant Clinical Diagnosis ill Ophthalmology (Refractive Sllrgery) Shack devices are outgoing testing devices in that they evaluate the light being bounced back out through the optical system. A narrow laser beam is focused onto the retina to generate a point source. The out coming light rays which experience all the aberrations of the eye pass through an array of lenses which detects their deviation. The wavefront deformation is calculated by analyzing the direction of the light rays using this lenslet array. Parallel light bea ms indicate a good wavefront and non-parallel light beams indicate a wavefront w ith aberrations, which does not g ive equidistant focal points. This image is then captured onto a ccd camera and the wavefront is reconstructed . The data is explained mathematically in three dimensions with polynomial functions. Most investigators have chosen the Zern ike method for this analysis although Ta ylor series can also be used fo r the same purpose. Data from the wavefront map is presented as a sum of Zernike polynomials each describing a certain deformation. At any point in the pupil, the wavefront aberration is the optical path difference between the actual image wavefront and the ideal spherical wavefront centered at the image point. Any refra ctive error which cannot be corrected by sphero-cylindricallens combinations is referred to by physicists as higher order aberrations, i.e. comma, spherical aberration, chromatic aberration. The Zernike Polynomials, which describe ray points, are used to obtain a best fit toric to correct for the refractive error of the eye. The points are described in the x and y coordinates and the third dimension, height, is described in the z-axis. The local refractive correction of each area of the entrance pupil can be determined by calculating from the wavefront polynomial the corresponding local radii of curvature and hence the required spherocylindrical correction. Thus each small region of the entrance pupil has its own three parameters that characterize the local refractive correction: sphere, cylinder and axis. The global aberrations of the entire optical system including the cornea, lens, vitreous and the retina are thus measured. The great advantage of wavefront analysis is that it can describe these other aherra tions.

The first order polynomial describes the spherical error or power of the eye. The second order polynomial describes the regular astigmatic component and its orientation or axis. Third order aberrations are considered to be coma and

fourth order aberrations are considered to be spherical aberration. Zernike polynomial descriptions for wavefront analysis typically go up to the tenth order of expression. The first and second orders describe the morphology of a no rmal straight curve. More local maximum and minimum points require

220

higher orders of the polynomial series to describe the surface. No rmal eyes exhibit spherical and coma aberrations in addition to exhibiting defocus and astigmatism. Ideally, the difference in the magnitude of the local refractive correction of eac h area of the en trance pup il s hould not exceed 0.25 D. Lowe r spherocylindrical corrections are generally associated with lower wavefront aberrations. These observations regard ing va riation in local ocular refraction

A berropia: A New Refractive EI1 tin)

Visual acuity in percentage in aberropic post zyoptix patients

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221

Instant Clinical Diagllosis in Ophthalmology (Refractive Surgery) along different meridians are also confirmed by Ivanoff and Jenkins. Van den Brink also commented on the change in refraction ac ross the pupil. Clinically significan t changes of at least 0.25 0 in one or both components of the spherocylindrical correction might normally be expected for decentrations of abou t 1 mm. Rayleigh's quarter wavelength rule states that if the wavefront aberration exceeds a quarter of a wavelength, the quality of the retinal image will be impaired significantl y. Thus the aberration in eyes starts to become significan t when the pupil diameter exceeds 1-2 mm. Thus it is not possible to correct the entire wavefront aberration with a single spherocylindrical lens. As conventional refractive procedures such as Lasikalso reduce only the second order aberrations, the visual ac uity w ill still be lim ited by aberrations of third and higher order aberra tions. These patients are likely to undergo tremendous improvement in their BCVA after correction of their aberrations by Zyoptix. in the Zyoptix system, the aberrometer and the orbscan, which checks the corneal topography, are linked and a zylink created. An appropriate software file is created which is then used to generate the laser treatment file. The truncated gaussian beam shape used in Zyoptix combines the advantages of the common beam shapes, i.e. flat top beam a nd the gaussian beam, creating a maximized smoothness and mininlized thermal effect. Thus Zyoptix gives a smoother corneal su rface, reducing glare and increasing visual acuity. The larger optical zones reduce haloes. Zyoptix also causes a reduction of the ablation depth by 15-20 % and a reduced enhancement rate. [n a patient with higher order aberrations, lasik does not remove the higher order aberrations and the pOint-spread function is a large blur. Zyoptix on the other hand, performs customized ablation and removes the higher order aberrations thus minimizing the wavefront deformation. The point-spread function is therefore a small spot of light. In our study, the mean preoperative spherical equivalent improved from -4.78 D to -0.16 D ± 0.68 and the mean preoperative cylinder improved from -1.34 D to -0.08 D ± 0.24. The aberra tions were reduced drastically in all the eyes and the BCY A improved in all cases by 2 two li nes. Reduction of the aberrations of the eye can thus result in an improved BCY A postoperatively. Improving the optics of the eye by removing aberrations increases the contrast and spatial detail of the retinal image. Reduction of higher order aberrations may not improve high contrast acuity much more in eyes where spherocylindricallenses alone improve the BCV A to 6/ 3 (2.00) or better. In contrast, in otherwise normal eyes where the BCY A is limited to 6/9 (0.50) or 6/ 6 (1.00) due to optical aberrations, reduction of higher order aberrations should improve visual acuity. Realization of the best possible wlai ded visual acuity may be limited at the cortical, retinal and the spectacle, corneal, or implant level. All maculae may not be able to support 6/ 3 (2.00) vision. insufficient cone denSity or sub-optimal orientation of cone receptors or a sub-optimal Stiles-Crawford profile of the 222 macula may make 6/ 3 (2.00) vis io n impossible. Clinical or sub-clinical

Aberropia: A New Refractive Ell tin}

Wavefront defomlatiol1

(~m)

Pre Eye OD NL: 3

o Wawfront defonnation (flm) Post Eye 00 Nr.: 1

Fig. SA

223

Instant Clinical Diagnosis in OphthalmologIj (Refractive Su rgenj) amblyopia ll1ay make achievement of super vision impossible. But in spite of this, there may be a certain patient population who have the potential for an improved BeVA on removal of their \,vavefront aberrations. The corneal topography does not account for the decreased preoperative visua l acuity in these patients, neither do they have any other identifiable cause for the decrease in acuity except for an abnormal wavefront. It is important that this subgroup of patients are identified and their optical aberrations neutralized so that they are not deprived of the opportunity to gain in their BeV A. Wavefront sensing technology, at present, does not in most cases define the exact locale of the pathology causing the aberration. Hence, clinical examination and other refractive tools, such as corneal topographic Inapping, along with sound clinical judgment is required for proper understanding of the eye and its individual refractive status. Also, wavefront aberrations may not relnain static. Numero us authors have sho,vn that ocular optical aberrations probably remain constant between 20 and 40 years of age but increase after that. Aberrations also ch ange during accommodation and may be affected by mydriatics. Thus, the patient should be informed about these possibilities while taking the consent for the procedure. Long-term studies are required to detennine the stability of the postoperative refraction, residual aberrations and changes in BeV A if any. The question of magnification facto r improving visual acuity does not arise as these patients preoperatively did not improve with contact lenses. Further the refractive error in some of these patients was not very large. CONCLUSION

Tn conclusion, removal of the wavefront aberration may extend the benefit of an improved BeV A to patients with an abnormal wavefront. The subgroup of patients vl'ith higher order aberrations, normal corneal topography and no other knm,v n cause for decreased vision may thus benefit immensely with \vavefront guided refractive surgery. Customized refracti ve surgery tailor-made for these individual patients, aimed a t neutralizing the wavefront aberrations of the eye is safer, more predictable, provides better visual acuities and reduces the incidence of w1satisfactory outcon1es. Further studies are required to assess the long-term outcomes. Till nm,v, when we discuss refractive errors we discuss about spherical and a cylindrical correction. But in todays world we have to think of a third parameter \vhich is the aberrations present in the eye which can be anyvvhere in the optical media. These can be corrected in the corneal level by the laser treatment.

224

Aben'opin:A New Refrnc tive E/ltih}

Wavefront defonnation (pm) Pre Eye OS Nr.:4

o WIl'.'l:front deformation (pm) Post Eye OS NT.:

Fig, 56 Figs SA and B: Pre and postoperative aberrometry of the right and left eye of the same patient showing removal of higher order aberrations

225

24 Topographic and Aberrometer Guided laser Amar Agarwal, Sunita Agarwal, Athiya Agarwal, Ashok Garg (India)

INTRODUCTION

Since as early as middle of 19th century it has been known that the optical quality of human eye suffers fro m ocula r errors (aberrations) besides the commonly known image errors such as myop ia, hyperopia and asigmatism. In early 1970's Fyodorov introdu ced the ante rior radial incisions to flatten the central cornea to correct myop ia. Astig matic keratotomy , Keratomileusis and Keratophaki3, Epikeratopha ki a and currently Excimer Laser have been used to manage the various refractive errors. These refractive procedures correct lower order aberrations such as sphe rical and cylindrical refractive errors however higher order aberrations persist, w hich affect the quality of vision but may not significantly affect the Snellen visual acuity . Refractiv e corrective p rocedures are known to ind uce aberrations. It is the subtle dev iations from the id eal optical system, which can be corrected by wavefront and topography gu ided (customized ablation) LASIK procedures. ABERRATIONS

Optical aberration custom iza tion can be corneal topography guided which measures the ocular aberrations detected by corneal topography and treats the irregularities as an in tegra ted part of the laser treatment plan. The second m ethod of optical aberra tion customization n1easures the wav efront errors of the entire e ye and treats based on these measurelnents. Wavefront analysis can be done either using How land's aberroscope or a Hartmann Shack wavefront sensor. These techniques measure all the eye's aberrations including second-order (sphere and cylindrical), third -order (coma- like), fourt h-order (spherical), and higher order w avefront aberrations. Based on this information an ideal ablation plan can be formulated w hich treats lower order as well as higher order aberrations. ZYOPTIX LASER

226

Zyoptix TM (Bausch and Lomb) is a system for Personalized Vision Solutions, which incorporates Zyvvave ™ HartrnalU1 Shack aberrometer coupled \vith

Topographic and Aberrometer Guided Laser

FIg. 1: Hartmann shack aberrometer

Fig. 2: Zywave projects low-intensity HeN e infrared light into the eye and use the diffuse reflection from the retina

227

b,stallt Clillical Diagnosis ill Ophthalmology (Refractive Surgery) Orbscan ™ II z multi-dimensional device, which generates the individual ablation profiles to be used with the Teclmolas® 217 Excimer Laser system. Thus this system utilizes combination of wavefront anal ysis and corneal topography for optical aberration customization.

ORBSCAN The Orbscan (BA USCH and LOM B) co rn eal topograph y sy stem uses a scanning optical slit scan that is fund am entally different than the corneal topography that analyses the reflected images from the anterior corneal surface. The high-resolution video camera ca p tures 40 light slits at 45 degrees angle projected through the cornea similarly as seen during slit lamp exan1inatiol1. The slits are projected on to the an terior segm ent of the eye: the anterior cornea, the posterior cornea, the anterior iris and anterior lens. The data collected from these four surfaces are used to crea te a topographic Inap . This technique provides more information about an terior seglnent of the eye, such as anterior and posterior corneal curvatu re an d corneal thickness. It in1proves the diagnostic accuracy and it has passive eye-tracker frOln fralne to frame, 43 fran1es are taken to ensure accu racy. It is easy to interpret and has good repeata-

bility. Three different maps are ta ken, and the one featuring the least eye rnovelnents is used. The maximum movements considered acceptable are 200 p.

ABERROMETER ZywaveTIvl is based on Hartmann - Shack aberrometry in \,v hich a laser diode (780 nm) gene rates a laser beam tha t is focused on the retina of the patient's eye. An adjustable collimation system compensates for the spherical portion of the refractive error of the eye. Laser diode is turned on for approximatel y 100 milliseconds. The light reflected fro m the focal poin t on the retina (source of wavefront) is directed through an a rra y of small lenses (lenslet) generating a grid like pattern (array) of focal points. The position of the focal points are detected by Zywave™ Due to de via tion of the points from their ideal position, the w avefront can be reconstruc ted . Wavefron t display show s (a) higher orde r aberrations (b) predicted phoropte r refraction (PPR) calculated for a back vertex correction of 15 mm. (c) Simulated point sp read function (PSF). Zywave™ examinations are done with (a) single exa mi nation with undilated pupil (b) five examinations with dila ted pupil (mydriasis) non-c ycloplegic, using 5% Phenylephrine drops. One of these five measurements, which matched best with the manifest refraction of the undila ted p upil, is chosen for the treatment.

ZYLlNK Information gathered fro m Orbscan and Z ywa ve are then translated into treatment plan using ZylinkTM software and copied to a flopp y disc k. The 228 floppy disc is then inserted into the Technolas 217 system, fluence test carried

Topographic alldAberrometer Gllided Laser

Fig. 3: Schematic illustration of the Bausch and Lomb Zywave aberrometer. A low-intensity HeNe infrared fight is shone into the eye; the retlee-ted light is focused by a number of small lenses (Ienslet-array), and pictured by a CeO-came ra. The capture image is shown on the bottom left

~.

Fig. 4: Technotas 217 z excimer laser system

229

II/stal/t Clil/ical Diagllosis ill Ophtha lmologtJ (Refractiv e SlIrgery) out and a Zyopitx treatmen t card was inserted. A standard LASIK procedure is then performed with a superiorly hinged flap. A HansatomeT>1 rnicrokeratome is used to create a flap. Flap thickness varied from 160).1111 to 200 ).1111. A residua l stromal bed of 250 ).lm or more is left in all eyes. Optical zone varied from 6 mm to 7 mm depending upon the pupil size and ablation required. Eye tracker is kept on d uring laser ab lation. Postoperatively all patients are followed up for at least 6 months. RESULTS

We did a study comprising 150 eyes with myopia and compolmd myopic astigmatism. Preoperatively, the patients underwent comeal topography wi th Orbscan II z ™ and wavefront ana lysis with Zywave ™ in addition to the routine pre-LASrK work up. The results were assimilated using Zylink T", and a customized treatment plan was form ula ted. LAS IK was then performed with Technolas® 217 system. All the patients were fol lowed up for at least six months. Mean preoperative Be VA (in deci mal) was 0.83 ± 0.18 (Range 0.33- 1.00). Mean postoperative (6 mo nths) BeVA was 1.00 ± 0.23 (Ran ge 0.33-1.50). Difference was statistically significa nt (p = 0.0003). Out of 150 eyes that underwen t customized ab lation, 3 eyes (2%) lost two or more lines of best spectade corrected visual ac ui ty (BSeVA) . Safety Index = Mean postoperati ve BSeVA/Mean preoperative BSeVA = 1.20. Mean preoperative UeVA was 0.06 ± 0.02 (Range 0.01-0.50). Mean postoperative UeVA was 0.88 ± 0.36 (Ran ge 0.08 - 1.50). Difference was statistically Significant (p = 0.0001). Efficacy index =Mean postoperative uev A / Mean preoperative uev A = 14.66. Preoperatively, none of the eyes h ad ueVA of 6 \6 or more and one eye (0.66%) had Ue VA of 6/ 12 or more. At 6 months post-operatively, 105 eyes (69.93%) had UeVA of 6\6 or more and 126 eyes (83.91 %) had UeVA of 6/ 12 or more. Mean preoperative spherical equiva lent was -5 .25 0 ± 1.68 0 (Range - 0.87 0 to -15 0). Mean postopera tive sphe rical equivalent (6 months) was - 0.36 0 ± 0.931 0 (Range - 4.25 0 to +1.25). Difference between the two was statistically significant (p < 0.05). 132 eyes (87.91 %) were within ± 1.000 of emmetropia willie 120 eyes (79.92%) were within ± 0.050 of emmetropia. 1 eye (0.66%) was overcorrected by > 0.5 0 and 1 eye (0.66%) was overcorrected by >10. The mean pupil d iameter was 5:1 mm ± 0.62 mm. Preoperatively, 95 eyes (63.27%) had third order aberrations.42 eyes (28%) had second order aberration alone, while 13 eyes (8.65%) had fo urth and fifth order aberrations. Postoperatively, 60 eyes (40%) had third order aberration.75 eyes (50%) had second order alone while 15 eyes (10%) had hig her order aberrations.

230

Topographic alld Aberrollleter Guided Laser

Safety-Change in BSCVA 6 months Postoperative

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100 90 ~ 80 ~ 70 '0 60 ~ 50 ~ 40 1$ 30 ffi .o"t»> 0,05 T-Student test). On the grounds of the 2 years long observation we conclu ded as follows 1. Th e use of mitomycin C allows qualifying for the LASEK p rocedure patients with large errors for w h om it would be dangerous to undergo the LASIK p roced ure due to insufficient cornea thickness. 2. N o side-effects of mitomycin C on the eye structure was observed in the studied group. 3. Based on the two years observa tion, the use of mitomycin C seems to be a safe method to prevent such comp lications as haze (confirmed by the confocal microscope examination). We did also resea rch on the process of cornea healing after the use of LASEK with the intraoperative MMC application in the correction of remaining refracti ve errors persisting after the LASlK procedure. We accepted the following indications for the use of LASEK after LASlK method in the correction of residual

280

refractive errors:

LASEK Procedure with the Use of Mitomycin C

Fig. 6: Anterior stroma 1 month after LASEK surgery- remains of scar tissue is visible

Fig. 7: Anterior stroma 1 month after LAS EK with adjunctive mitomycin C- no scar tissue remaining

281

Instant Clinical Diagnosis in Ophthaltnologt) (Refractive Surgen)

1. Stable refractive error from -1.0 0 , to -4.0 0 , astigmatism from - 1.0 0 to 2.5 0 2. Lack of patient's acceptance of the offered optic methods 3. Symptoms of dry eye syndrome in the period of 3 months after the LASIK procedure (contraindicated classic reopera tion) 4. Massive OLK after the primary procedure 5. Conditions after remova l of epithelium in case of ingrowth's under the flap 6. Irregular circular scar in the fla p's cut place Disorders of corneal structure were not demonstrated in preoperative confocal microscopy examina tion excluding presence of depOSits of medium and high reflectivity on level of interface and reduction of keratocytes density in this place. In some of the cases anomalies in the course of nervous fibers were stated. Postoperative confocal microscopy examination showed the presence of scar tiss ue under the epithelium and in the anterior part of proper substance in operated patients. On examinations performed 3 months after the procedure almost no scar forma tion w ar observed. Presence of pathological changes such as augmented number of excited keratocytes, presence of need le-like formations or infiltrative cells were not noticed either in examination 3 months after the procedure. Appearance of the epithelium did not differ from the phYSiologica l one except from insignificant thinning in the superficial layers in par t of the cases. It indicates the proper course of healing process No corneal haze was noted in the slit-lamp examination after LASEK reoperation in the analysed group . LASEK with MMC in our opinion seems to be a safe method for correction of residual errors after previous LASIK. SUMMARY

"According to Dr. Liberek, they perform LASEK when the cornea is less than 500 fIm thick, and they apply MMC when the patient is abou t -5 0 and the ablation depth needs to be more than 60).UIl . "Without MMC, [LASEK] would not be possible because [the case] wo uld be high myopia, and with high myopia, we observed haze," If MMC is not availab le, and the patient has more than -10 0 of myopia, phakic IOL use is indicated "To choose the phakic IOL or LASEK with MMC, so it depends on the cornea and the pachymetry, and it depends on the high refractive error." 282

LASEK Procedllre with the Use of Mitomycill C

Fig. 8: Unchan-ged endothelium in patient 12 month after LAS EK with adjunctive mitomycin C surgery

Fig. 9: Before LASEK surgery-very hyper-reflective deposits at l ASIK interface depth, the

keratocytes density is locally decreased

283

Installt Clinical Diagnosis in Ophthalmology (Refractive SlirgenJ)

Fig. 10: Sub-epithelial opacities (scar tissue) is reflecting light under healthy basal epi - thelium~ 1 month after LASEK surgery

Fig. 11 : Anterior stroma 3 months after LASEK surgery, no scar tissue detectable

284

LASEK Procedure with the Use of Mitomycill C

90% 77.70%

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22.30%

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285

30 Transepithelial Cross-linking for the Treatment of Keratoconus Roberto Pinelli, E Milani (Italy)

INTRODUCTION

Keratoconus is a non-inflanlmatory cone like ecstasia of the cornea, which is

usually bilateral and progress over time, with consequent central or paracentral thinning of the stroma and irregular astigmatism. The relevance of keratoco n us in the general population seems to be relatively high, with approximately 1 in 2000, even if the diffusion of new diagnostic means will permit to find prevalence rates certainly greater. In nearly all cases both eyes are affected, at least from a topographic point of view. The cause of keratoconus is unknown, but it seem s that enzymatic changes in corneal epithelium, such as a decrease of the levels of the inhibitors of proteolytic ezymes and an increase of the lysosomal enzymes can be involved in the cornea degradation. At the begirming, glasses are sufficient to correct myopia and astigmatism still regula r or slightly irregular; successively, in cases of high astigmatism, it becomes necessary to apply hard contact lenses. Epikeratoplasty is effica cious in patients which do not end ure contact lenses and which do not show a significant central corneal opacity, but, due to its v isual outcomes not perfect,

it was dropped. Intracorneal rings also can be an option, but all these described techniques unfornmately only correct refractive errors and do not treat tl,e cause underlying the corneal ecstasia and therefore they do not permit to stop the progression of keratoconus.

In 1996 some theo retical studies sta rted investigating more deepl y the underlying causes of keratoconus and the possible parasurgical techniques to stop its progression. In all patients affected by keratoconus a reduced degree of cross-links in the corneal collagen fibers has been observed; that is, the aim of those studies was firstly to determine how to increase those cross-links to obtain an improved mechanical stability of the cornea and increase the resistance against enzymatic degradation.

286

Trallsepitllelial Cross-linkingfor the Treatment ofKeratoconlts

Fig . 1: Keratoconus

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Fig . 2 : Collagen triple helicoidal chain

287

Instant Clinical Diagnosis in Ophthalmologt) (Refractive SlIrgen)) CORNEAL COLLAGEN NETWORKS

Collagen is a structural protein organized in fibers. Those fibers are responsible of limiting the tissue deforma tions and preventing mechanical brakes. The collagen fibers are chemically stable and have high mechanical properties. Inside the connective tissue, fibroblasts synthetize tropocollagen molecules, the base blocks of collagen fibers. Those molecu les have a typical weight of 300 kDa, a length of 280 nm with an average diameter of 1.5 nm. The molecule is composed by 3 helicoidal chains (alpha-chains) interlaced each other like a rope. The fac tors of stabilization of those collagen molecules are related to the interactions between the 3 helics and are due to Hydrogen links, Ionic links and intra-chain reticulations (cross-links) The stroma, composed mainly by collagen lamellae, gives to cornea 90% of its thickness. Between the lamellae keratocites can proliferate, migrate and turn into their active state. Integri ty of corneal epitheli um for the switch of keratocites (resting cells) in fibroblasts (active cell) is very important. Cheratansulphate type I is the most important mucopolysaccharide present in corneal stroma: it plays an important role for the orientation of collagen mashes and lamellae (corneal clarity, tensile strenght) and for corneal hydration (corneal edema). PHOTOCHEMICAL CROSS-LINKING

There are many different possibilities of cross-linking: • Lysyl oxidase (LOX) cross-links collagen enzymatically • Transglutaminase (12 h, pH=3) • Sugar aldehydes (d iabetes - Advanced Glycation Endproducts AGEs) • Chemical cross-linking (glutaraldehyde, formaldehyde, DPPA) • Photochemical cross-linking (UV, ionizating radiation) The interaction between organic tissues and radiation depends on the type of radiation used. The ionizing radiation has enough energy to turn out electrons from the atomsofthe tissues. Other types of radiation, i.e. UV radiation, ha ve not enough energy to turn out electrons but to make them jump to higher energy levels (exciting radiation). In the human biologic tissues, water molecule is present at a rate of 70 to 90% so it is clearly the main target of radiation . During the water radiolysis process, the energy applied to water molecules ionizes them ad generate free radicals molecu les. Free radicals are continuously produced in tissues and quickly inactivated by chemical or enzymatic transformation. In the eye, ascorbic acid absorbs UV radiation (a t cornea, lens and vitreolls

288

body d istricts); it is a cofactor of several enzymes, the best known of which are

Trallsepitheliai Cross-linking/or the Treatment o/Keratoconus

Fig . 3: UVA sou rce (Courtesy of Peschke GmbH)

1·Combined application of UVA and riboflavin Riboflavi n (Vii. 8 2) Ultraviolet irradiation O-H /

H, C

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Collagen fibril

Collagen fibril

Fig . 4: Photochem ical induction of cross-links

289

Instant Clinica l Diagnosis in Oplrtlralmolofflj (Refractive Surgenj)

prlyne hyd roxylase and lysine hydroxylase, enymes involved in byosinthesis of collagen. In vitreous body, after cataract surgery (absence of glutathione), ascorbic acid (in ascorbate form) absorbs UV not stopped by lens, resulting in the formation of free radicals, d isaggregation of hyaluronic acid and increase in cross-linking of collagen fiber networks. RIBOFLAVIN-UVA TREATMENT

A photo sensitizer is a substance which is activated by the absorption of light ata given wavelength and which can induce free radical reactions in its activate form. This substance can amplify light radiation effects on biologic tissues. The basic mechanism of the photochemical treatment of ke ratoconus is to use riboflavin as a photo sensitizer and apply on it UV irrad iation at a determined wavelength to induce free radicals reactions and increase this way the cross-links in the collagen fibers. Riboflavin has a high UV absorption between 360 nm and 450 nm; due its additional shielding all structures behind the corneal stro ma, including corneal endothelium, anterior chamber, iris, lens and retina, are exposed to a residual UV radiant exposure less than 1)1 cm2 (in

accordance with safety guidelines). The UV source is typically a group of 3 to 5 Light Emitting Diodes producing a radiation of 370 lUll wavelength and 3rnW Icm 2 intensity. The cross-linking effect is obtained in 3 steps. CORNEAL EPITHELIUM

The w idespread technique of cross-linking is based on a central corneal abrasion (with a diameter of 8 mm). This abrasion is made because the epithelium is believed to be a barrier to the correct diffusion of riboflavin so a possible factor of decreased effectiveness of the treatment. What has been observed during the different studies is that free radicals mediated by the riboflavin irradiated with UV light can create cell damage. Keratocytes showed (in both laboratory and clinical studies in epitheliumremoved eyes) cells dea th upto a 350 J.lm depth. After 6 months the area is repopulated by keratocites which, differently from corneal endothelium, can reproduce. To preserve the endothelium a minimum corneal thickness of 400 nm should be assured. The news in this treatment is represented by the possibility of realizing cross-linking keeping the epithelium unaltered. This natural barrier protect the cornea but it is not an impermeable stratus: it is an osmotic membrane thru which the riboflavin can penetrate to the cornea. Of course the riboflavin itself can not penetrate eaSily so the question is, at this stage, abo ut the real effectiveness of the treatment, compared with the "official" one. If we combine 290 the riboflavin drops w ith a tense-active substance, we can have a more efficient

Transepith elial Cross-linking/or the Treatment o/Keratoconus

Fig. 5: Patient eye under C3·R treatment

penetration to the cornea. This substance act as a vector for riboflavin, w ith a

double effect: reaching the cornea and filling the epithelium, contributing so far to its strengthening. The advantages of this particular technique is tha t all the macroscopic side effects related to the epithelium-removal technique are not present: no pain, no stromal edema (due to the ab rasion) and, more important, the possibility to treat both eyes in the same session (85% of patients has bilateral keratoconus, so the treatment is in most cases necessary in both eyes). Even if we assume that the riboflavin can no t penetrate efficiently the epithelium, we think that as the photo sensitizer is distributed homogeneously on the trea ted eye, we can at least obtain an increased rigidity of the corneal epithelium, thus a decreased instability in visual acuity of the patient. The rea l question is abo ut the effectiveness of the treatment, as the safety issues are not a worry of this technique: keeping the epithelium unaltered means reducing most of the side effects of the trea tment (included the death rate of keratocites and the number of endothelial cells). We continue our studies in this way because we believe that the epithelium removal is something that could be avoided in the treatment and transepithelial tecnique will become the standard in Cross-linking treatments. 291

31 Sub Bowman's Keratomileusis: Combining the Best of PRK and LASIK for Optimal Outcomes Daniel S Durrie (USA)

Photorefractive keratectomy (PRK) and laser in sit" keratomileusis (LASIK) have drawbacks in terms of technique and outcomes that are well known to both consumers, as well as physicians. Which begs the question-what if we could create a procedure that combines the best of these two techniques while leaving behind the negatives? Could a procedure like this win over skeptics and help create renewed interest among consumers in corneal refracti ve surgery? Sub Bowman's Keratomileusis (SBK) is a hybrid of PRJ< and LASIK that is designed to provide a superior method for performing corneal refractive surgery. This technique involves the use of a customized corneal flap of between 90 and 110).lm with diameter that is closely matched to the ablation zone of the excimer laser being used, typically 8.5 mm or less. Although there are mechanical microkeratomes capable 01 the creation of the thin corneal flap, the critical component in SBK is the use of a femtosecond laser for flap creation. This is due to the ability to the femtosecond laser to create an almost planar corneal flap. This allows for better predictability, as well as flap creation having less of an impact on the excimer laser ablation, as has been shown in studies wi th mechanical nticrokeratornes. With mechanical microkeratomes, the cornea l flaps are more meniscus in shape and are thinner in the center and thicker in the periphery. This chapter will explore the evolution that has led to SBK, the biomechanics of the procedure and then review a clinical study com paring a myriad of outcomes of SBK vs. PRK. The Evolution The argu ments in favor of PRK and LASIK are well documented. Some of the pros for LASIK include the patient pleaSing benefits of quicker visual recovery and less postoperative pain. On the con side of LASIK are dry eye, 292 flap comp lications, as well as the risk of cornea ectasia - although this last

Sub Bowman's Keratomilellsis: Combining tile Best of PRJ( and LASIK

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293

Instant Clinica l Diagnosis in Ophthalmology (Refractive SurgenJ) point remains up for debate. On the pro side for PRJ< are fewer complaints of dry eye, better correction of high-order aberrations (HaAs) and better quality of contrast sensitivity and night vision. On the can side are slower visual recovery, more pa in particularl y in the immediate postoperative period, as well as the risk of haze. Advocates of LASIK and PRK, as well as newer procedures such as epiLASIK and laser epithelia l keratomileusis (LASEK), claim superiority when it comes to visual results. However, the published literature indica tes that visual outcomes are relatively equal between surface ablation techniques and LASIK, and that LASIK patients demonstrate better visual results during the first 4 postoperative weeks. The most notable of these papers is a Cochrane Collaborntion Methodology meta-analysis/ systemic review conducted by Shortt and Allan. As part of this analYSiS, the authors reviewed all published prospective and randomized controlled studies, along with the database of the US. Food and Drug Admini stra ti on of all LASIK and PRK studies conducted for US approval. Shortt and Allan concl ude that LASIK is safer and more accurate than PRK, however, taking note tha t most published studies are pre-200l and do not involve current technology or algorithms. A number of studies published in the latter half of 2006 and 2007 do compare LASIK against LASEK, epi-LASIK and PRK . A control -match comparison of LASIK and LASEK done at the Massachusetts Eye and Ear Infirmary looked at outcomes in a matched group of LASIK and LASEK eyes and foun d that the results were relatively similar with a mean postoperati ve UCVA of 20/ 21 in the LASEK group and 20/ 23 in the LASIK group. Two studies explore postoperati ve pain in surface ablation procedures. The first, from Mexico, looked differences in early postoperative pain between epi-LASIK and PRJ< in a prospective, comparative, bilateral study. The results showed that patients had similar pain in their epi-LASIK and PRJ< eyes on Day 1, but that the epi-LASIK eye was more painful On Days 3 and 6. The second stud y, from lreland, compared pain response in epi-LASEK, LASEK or PRJ 6/6.

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383

Ills tallt Clillical Diagn osis ill Oplltl1flll1lo1ogtJ (Refractive Surgery) HINGE PROTECTION

This is a special feature available with the PULZAR Zl, which au tomatically protects the hinge in LASIK or Epi-LASIK trea tments. After selection of the position of the limbus the surgeon can enter the distance of the flap hinge from the limbus then the software will not fire a single pulse from the limbus to the hinge. Advantages of Hinge Protection

• No need to constantly monitor flap. • No laser pulses w ill be fired on the hinge, decreasing the chance of astigmatism or over-correction being induced by laser ablation over the hinge. • More predictab le and accurate results can be achieved. AUTO-CENTRATION

The PULZAR Zl software provides an automated beam-centration procedure that allows the user to align the laser beam if it is observed to be decentered during the da ily system checks. It takes empirical measurements through the eye-tracking system to ensure that the beam is correctly positioned at the treatment plane. AUTO-CALIBRATION

The system ca libration is an automa ted procedure in the PULZAR Zl. This ensures accuracy of the system's laser output and automatically adjusts the internal operating parameters accordingly if required. Advantages of Auto-calibration

• Being an automated proced ure it avoids chances of human error. • No need to have expensive fluence plates as required by excimer lasers • Set up time is fast as calibration time is about one minute - no need to

manually adjust fluence of laser FREEDOM TO SELECT TREATMENT CENTER

The PULZAR Zl allows the surgeon to select the treatment center for standard treatments accord ing to their preference. An image is captured while the patient is on the bed and the surgeon is free to select the pupil-center, corneal vertex (center of the ring light) or any other location they deem appropriate.

384

Solid State Lasers for Refractive SlIrgenJ Hyperopia and mixed astigmatism Postoperative UCVA Al lalest foltow ·up of 3 months (n; 195)

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385

II/stant Clil/ical Diagnosis in Ophtha/mol0I5'J (Refractive Surgery) CORNEAL HYDRATION DURING ABLATION

213 run has a special characteristic. As 213 nm lase red pulse is deli vered on to the corneal bed it will produce a fluid over the corneal surface. 193 run laser (Excimer Laser) behaves in the exact opposite way by drying ou t the cornea. As 213 run is less affected by the hyd ration or fluid on the cornea, there is no need to contin uously wipe acc umu lated fluid. Fl uid over cornea will allow patient to have a more clear view of the fixation target than 193 run lasered dry cornea. It allows patients to fix their eye very well during whole treatment reducing chances of decentered treatmen t and increases comfort for patient and surgeon. Figures 14A to D clearl y show the production of fluid over corneal bed as 213 nm laser fires. NOMOGRAM ADJUSTMENT

The 213 nm laser wavelength has increased penetra tion depth through sodilun chloride and balanced salt solution. It proves to be very good fo r laser vision correction as it has very little effect from hydra tion. These allow us to compensate as best we can for hydration issues related to surgeon techniques. While 193run excinler laser resu lts depend on the corneal hyd ration or environmental humidity requiring personalized nomograms for every surgeon. ANYTIME SURGERY - FREEDOM TO DO SURGERIES AT YOUR CONVENIENCE

Anytime Surgery is pOSSible onl y with the Solid State Laser as there is no need to charge or refill gases. You can just switch on the laser and start doing surgeries w ithin 5 minutes (Dramatically reduced warm lip time). There is a no need to keep special surgery days, as there is no extra cost involved in doing surgery at any time and any number of eyes, may be even a Single eye. LESS MAINTAINANCE AND COST

Electricity - 10 Amp supply with a maxim um of 2400 watts is the requ irement to run Solid State Laser. This is much less than excimer lasers enabling a reduction in energy bill. Gas - N o need to use any toxic and expensive gases any time for refractive

surgery. No more worries for transport and storage of ArF gases. It will save a huge amoun t of money over a period of time. Replacement of optics - Absorption peak of optics is near 185 nm. 193 nm is close to 185nl11 causing damage to optics more frequently than 213 nm which is little longer wavelength and away from 185 nm. It will allow us to replace optics less frequently than with excimer lasers. Less downtime - The long term stability of the Solid State Laser indicates a 386

minimum down time over the year.

Solid State Lasers for Refractive 5l1rgenJ SAFETY FEATURES Foot Switch

A footswitch is built into the system . The surgeon enables treatment by depressing the footswitch after the software has been told to start the treatment until the treatment is completed. As such, the treatment can be paused and resumed at any time by removing their foot from the footswitch. The computer automatically d isables the footswitch at the end of the operation to p revent accidental firing of the laser. Laser Enable Button

The laser enable button is included as a safety precaution intended to preven t the laser from firing following an interrup tion of normal operating conditions. The button must be pressed after switching the system on, after the interruption of the system mains supply or after the emergency stop button has been activated to allow the laser to fire. Emergency Stop Button

The emergency stop button, when pressed d isables the laser, bed and control panel but does not d isable the system computer or touchscreen moni tor. The button is intended to be used only in case of emergency to stop the laser firing or to prevent movement of the bed which could potentially result in danger to the patient. TREATMENT PLANNING In the PULZAR Zl system standard treatmen ts can be planned directly on the

device and custom treatments, both topography and wavefront based, can be planned on a separate PC using the CustomVis ZCADTM custom treatment planning software and transferred to the laser via CD-ROM.

STANDARD TREATMENTS Treatments are designed to alter the curvature of the cornea by a given astigmatic ma nifest refraction, within the entirety of the optical zone. The size of the optical zone is entered as a diameter in millimeters. A spectacle distance must also be provided to correctly interpret the refraction. Standard treatments also require an average preoperative keratometry input in diopters to accurately ap ply the refracti ve correction to corneas of all sizes.

387

Instant Clinical Diagnosis in OphthalmologtJ (Refractive Surgery) STANDARD TREATMENT FEATURES IN PULZAR Z1 Maintenance of Preoperative Corneal Asphericity

Standard treatment performed w ith the PULZAR ZI, maintain preoperative asphericity of the cornea. This helps to prevent the introd uction of high-order aberrations. This feature increases patient comfort and postoperative visual quality. Saving Entered Treatments

Patient trea tmen ts can be saved and stored for later use. This gives the surgeon the ability to enter all p atient data prior to surgeries allowing surgeons to save time on the day of operation. The trea tment to be performed can be selected from a lis t of treatments not yet perform ed. In addition, past trea tments can be reviewed. Resuming an Aborted Ablation Process

If, for an y reason , the surgeon needs to ab ort a treatmen t then the aborted treatment can be eaSily recommenced by selecting from a list of incomplete treatments. The treatmen t will then be res umed from the exact pulse that it was aborted on , e .g. if a treatmen t was aborted after the 1000th pulse then the treatment w ould be recommenced starting from the 1001st pulse. This fea tures reduces the severity of issues such as power failure that fil ay require a treatment to be aborted by allowing the original treatmen t to be completed a t a later time from where it left off. CUSTOMISED TREATMENTS

The Custom Vis™ Puizar'" Zl laser system is specifically designed to facilitate custom refractive surgery. Rather than sim ply modifying existing technology that was intended to perform standard procedures, Custom Vis combines a number of proprietary technologies designed from the ground up to satisfy the requirem ents of custom surgery. One such technology is ZCADTM, an intelligent surgical planning system that is used to create a unique treatmen t plan for each eye, ens u ring tha t each patient is treated in dividually. ZCADTM integrates information from various diagnostic sources including topog raphy, wavefront analysis, pupil size, pach ymetry and refractive data, and allows the surgeon to alter the treatment zone, optical zone an d refraction param eters to determine the optimal treatment plan. ZCADTM also simulates the post-op erative corneal top ography, ensuring that surgeon s are satisfied with the projected treatment outcom e. The treatment p lan is then tran sferred to the PULZAR ZI system via a CD.

388

Solid State Lasers for Refractive Su rgery Special Features of ZeAD

Freedom of Choice of Optical Zone and Treatment Zone • Ideal to maximize resu I ts for higher corrections

• Optical zones from 2-9 mm for sphere and cylinder available for all treahnent types • Great way to optimize tissue abla tion. Refraction Adjustments - Surgeon's Choice

• Flexibility for fine adjuShnents in refraction in 0.01 0 steps • Wavefront and topography data ca n be used together • Allows surgeons to plan more individualised treahnents. Automatic Cylinder Notation Conversion

• Surgeons can program treahnents in any cylinder notation - our software automatically converts it into the most tissue-saving ablation pattern • More safety for surgeon and the patient by the saving of tissue and allowing a higher refracti ve correction. Corneal Asphericity Customization

• PULZAR standard treatments allow the surgeon to maintain the preoperative asphericity of the cornea • ZCADTM provides the flexibi lity to select the postoperative corneal asphe ricity • Surgeons can choose postoperative eccentricity appropriate to the pre-

operative asphericity of the cornea. 6 d ifferent options are ava ilable for postoperati ve eccentricity. Depth Offset • This feature allows the surgeon to save tissue or ablate additional tissue

if the need arises, e.g. in PTK trea tments. • The depth-offset allows PTK treatments to be performed either at the same time as a refractive procedure, or independently by entering zero subjective correction.

• The depth-offset also allows the maximum depth of the plan to be reduced by entering a negative offset, provid u1g a means of saving tissue that is particularly useful in highly irregular cornea requ iring custom treatment. • The dep th offset feature is also available for standard surgeries U1 Pulzar.

389

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) CT Sca le

• Custom treatments take a CT Scaie (Corneal topography scale) parameter that weights the influence of the topography on the trea tment plan from zero (topography is ignored) to 1 (full topography-based p lan). This allows for finer control over topography-based treatmen ts and provides a means of planning a s€ln i-custom treatment with a more tailored plan than a s tand ard trea tmen t bu t w ith less tissue loss th an a full custom treatment. ZCADTM can generate custom trea tment plans based on topography data alone, or a combination of wavefront and topography data. ZCADTM currently suppor ts the Tracey'" VFA wavefront an alyser and associated EyeSys® top ographer as well as the Orbscan'" top ographer. Cu stom treatments support all the parameters accepted for standard treatments w ith the exception of the APK (Average Preoperative Keratometry) setting which is in s tead calc ula ted m ore accurately fr om the corneal topograph y, allowing p lans to be created more appropriately for aspherical con1eas. Custo m treatments incorporating wavefron t data calculate an auto-

refraction based on a combination of the wavefront and topography data and compare this to th e entered manifes t refraction. If a significant difference is observed then the user is given the op tion of using the manifes t refraction, the auto-refraction calculated from the w av efront exam or to use the auto-refracted

astigmatism but with the manifest spherical equ ivalence. ZCADTM also provides a simula ted postoperative top ography p rovid ing a means of verifying the treatment p lan 's suitability to the patient. Finally, the pupil and limbu s n eed to be selected on an image of the subject taken at th e time of the preoperative exam s fo r registratio n purposes. Both ZCADTM and the Pulzar'" software provide an auto-detection fa Cili ty to detect the pupil and limbus, requirin g only minimal adjustment in most cases. Once treatment generation is complete, the treatrnentdata needs to be written to a C D. This CD then contains all the d ata required for PULZ AR to p erform the customised surgery exactly as p lanned. TRACEY WAVEFRONT ANALYSER

The TraceyTM visual function analyser utili zes fundamental thin beam principle of optical ray tracing, an d combines it w ith th e EyeSys® corneal topography . The iTrace, a unique wavefront device, intended to solve the 'science of refraction' u sing a delivery method adaptable to eye care, w hich is quick and easy to use. The instrument, capable of measuring both lower and higher order aberrations of the eye, while separating lens and corneal aberrations, is unique in ll1any ways w hen compared to s impler wavefront devices that are available

390

Solid State Lasers fo r Refractive Slirgery

today. By an alysing the refracti ve power of the eye consistent with the optical path in natural vision, that is rneasurin gfonvard aberrations as thin beams of light pass through the cornea, pupil and lens to focus on the retina, the iTrace can:

• Rapidly measure one point at a time, separately, to avoid overlapping or d ata confusion. • Projects 256 points in to a pupil as small as 2 mID or as large as 8 mm • Obtain a high d ynamic range, from -150 to +150 • Measure light rays going in to the eye, instead of coming out of the eye • Detect the retinal location of each thin beam going in the eye to generate a true retinal spot pattern • Avoid becoming compromised by opacities or other opaque or irregular areas • Separate out corneal aberrations from lens aberrations using the ability to register with corneal topography. Data Displays

The iTrace d isplays the data it processes in various ways using combinations of both lower and higher order aberrations (total aberra tions), and higher order aberrations a lone. The data can be viewed as simulations of what the patient actually sees, colour coded maps in- diopters or microns of wa vefront error, and as bar graphs or charts of Zemike terms. There are 6 types of d isplays, 1. Wavefront total and Wavefront HOA 2. Refrac tive total and Refractive HOA 3. PSF total and PSF HOA 4. Snellen letter total and HOA 5. Zernike chart 6. Lens aberration analysis. Other Advantages of Tracey

1. Detects night m yopia

2. Uncover latent hyperopia 3. Measure acconunodative volmne 4. Reduce need for cycloplegic refraction by performing a true distan t exam binocularly. Tracy and Custom Vis Pulzar Z I

Custom Vis and Tracey technologies have formed an ag reement for the supply of iTrace Visual Function Analysers that have been specifically configured to export topography and wavefront aberrometry data to the ZCADTM planning software.

391

Instant Clil/ical Diagl/osis in Ophthalmologlj (Refractive SII I'genj) CLINICAL OUTCOMES

The PULZAR Zl has been used for the treatment of virgin eyes, the re-treatment of patients who have had sub-op timal outcomes from previous refracti ve surgery as well as irregular astigmatism. LASIK, LASEK and PRK have been performed. Latest Clinical Results

The PULZAR Zl has been used to trea t a wide range of myopia, myopic astigmatism, hyperopia, hyperopic astigmatism and presbyopia (presbyopia is un der clinical trials). More than 12,000 eyes with highly satisfactory results were treated at more than 9 international sites; the PULZAR has been used effectively and regularly to treat standard and custom surgery. Myopia - Moderate to High (Up to -14.50 Sphere and up to -5.50 of Astigmatism)

Four hundred and thirty six eyes were followed for a minimum of three months (Upto -14.5 D sphere and up to -5.5 D of astigmatism). Out of436 eyes, 367 eyes (84%) were within half a diopter of intended refractive correction and 428 eyes (98%) were w ithin one diopter of intended refraction. A total of 27 eyes gained one line in their Best Spectacle Corrected Visual Acuity (BSeVA) and noeye lost more than 1 line of BSCVA. 74 % of eyes had 6/ 6 or better uncorrected visual acui ty (UeV A) and 88% had 6/ 7.5 or better UCVA. Attempted Vs Achieved graph

195 hyperopic eyes were followed for 3 months. Preoperative SE was upto + 6 o and mixed astigmatism were up to -6.5 D. 68 % were within + / - 0.5 0 of intended refractive correction and 88% were w ithin + / - lO af intended refractive correction 86% of eyes had 6/6 or better u e v A. Cu rrentl y presbyopia softwa re is under clinical trial s at var iou s international clinica l sites. More than 100 eyes have been treated with new multi-zone presbyopic software. Cen tral and peripheral zones were used for distance vision and a middle zone was used for near vision . All patients had very good near and far vision though near vision was better than far vision. the presbyopic software will be available commercially as further trials confirm the early results. The presented clinical da ta supports the safety, predictab ility and effectiveness of the PULZAR Zl Solid State Refractive Laser (213 nm) for the correction of a whole range of refraction including high myopia, hyperopia, mixed astigmatism and presbyopia. 392

Solid State Lasers for Refractive Surgery THE BOTTOM LINE

Solid State technology promises to meaningfully advance the state of the art in refractive laser surgery by streamlining design, increasing predictability of results, improving results and eliminating the need for high voltage power sources.

The clinical ad vances that stand to be gained are related to precision and predictability. Predictability will be enhanced, in the larger part because the laser energy at 213 nm can pass through the NaCL 0.9 % and BSS (Balanced Salt Solution) with very little energy loss. As a resu lt, a 213nm laser's performance is less susceptible to variations in humidity or corneal hydration. The precision of the solid state laser system, now clinically proven, is a result of enhanced tracking and ultra fa st scanning, which also supports a faster pulse rate. Clinical results from all international sites are promising, exceeding the expectations of patients and surgeons. Solid State Laser is a good alternati ve to the current excimer laser. It also looks to be the future of Refractive Laser Surgery.

393

38 Dry Eye after Refractive Surgery Belquiz A Nassaralla, Joao J Nassaralla Jr (Brazil)

INTRODUCTION

The past two decades have seen changing trends in refractive surgery, with the evolution of several different procedures. Reshaping the anterior corneal surface by excimer laser photorefractive keratectomy (PRK), laser in situ keratomileusis (LASLK) or laser subepithelial keratomileusis (LASEK) has shown considerable promise for the surgical correction of refracti ve errors. Ln PRI112 (~J

--------------------. H.J m ..J.. ~~r$Y Fig. 1: Pathfinder example

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optical pach ymetry. Many systems employ neural netwo rks to aid clinicians with indices ind icating the likelihood of diseases such as ke ratoconus and pell ucid marginal degeneration, or if the patient has unde rgone refractive surgery. Examples of such programs are the Zeis-Humphrey Atlas' Pathfinder program and Nidek's Magellan detailed statistic analysis. Other systems combine wavefront aberrometry and corneal topography to produce corneal wavefronts which allow aberrations from the lens to be differentiated from those of the an terior cornea. Clinicians are often more comfortable with wavefron t then elevation represe n tation of corneal abnormalities. An example is shown in Figure 3. Such technology is used to differentiate the cause of vision loss when more than one pathology is present. Topographers have moved past the an terior surface to view the posterior surface and allow pachymetry withou t touching the cornea. The Orbscan (Bausch and Lomb, Rochester NY) slit scanning device was the first to visualize the posterior surface and perform optical pachymetry. However, the orbscan fails to correctly identify the posterior surface in patients SI P LASIK and pachymetry measurements showed increased va riability. Scheimpflug photography gave birth to the Pentacam (Oculus), a three dimensional anterior segn1ent imaging system which also allows measurement of the posterior surface of the cornea and optical pachymetry (Gulani AC. Pentacam Basic and Advanced course: KMSG Conference- Madrid, Spain, July 2006). These systems may be better at identifying risk factors for ectasia following refractive surgery, as well as to evaluate patients followulg surgical complications, such as flap tea rs, scarring and straie (Gulani AC. Pentacam in Full Spectrum Refractive Surgery: Ad vanced Corneal Topography CourseAAO, Las Vegas. Nov 2006). Highl y detailed pachymetry maps such as that in Figure 4 may indicate early keratocon us in patients seeking LASIK. The Pentacam measured central corneal thickness values closer to ultrasound pachymetry and with less variability then Orbscan. It was also found to have the highest rep roducibility compared to Orbscan and ultrasound. Also new to the refractive scene is ocular coherence tomography (OCT), a noninvasive optical imaging techniq ue that was previously used to inlage the posterior segment. OCT instruments use optical interferometry to generate a log reflectivity profile describing the different layers of the cornea and allow the separation of reflective structures to be measured. OCT also yields optical pachymetry values across the cornea. Surgeons prefer optica l pachymetry. Several systems now measure pach ymetry optically, and yield pachymetry values across the cornea, allowing identification of thin spots much like topography yields steep areas of curvature. This is especially important to refractive surgeons evaluating patients for elective keratorefractive surgery_

Ultrasound remains the standard for pachymetry, but it does have its drawbacks. There is a high degree of reproducibility but the probe does 408 require anesthesia and direct contac t with epithelium. It is a single-spot

Future of LASIK Surgery

Fig. 3: Tracey corneal wavefront example

Fig. 4: Pentacam pachymetry map In a patient with early keratoconus

409

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) measurement with limited precision. Slit-scanning yields pachymetric maps but is less accurate. Pentacam appears to be more accurate but is not able to differentiate the layers of the cornea. Ultrasound imaging can map these layers but requires a cumbersome waterbath technique. OCT has been shown to yield values similar to ultrasound in virgin as well as cornea SIP LASIK. OCT yields detailed pachymetric analysis and visualizes the layers of the cornea. This is beneficial in patients SI P LASIK seeking enhancements or those needing progression analysis of keratoconus. Such an example is shown in Figure 5. This technology is invaluable for surgeons attempting to correct complications from previous surgery such as flap trauma and repeated enhancements. SURFACE TREATMENT VS LASIK

These advancements in technology have increased our understanding of the posterior surface and corneal biomechanics SIP keratorefractive surgery. PRK was initially used with excimer lasers, and the associated pain and risk of corneal hazing are well known. The haze results from damage to the epithelium and stroma simultaneously during the procedure, resulting in cross talk between the stromal keratocytes and epithelial cells. LASIK was preferred due to the quick visual recovery, significantly less pain and convenience for patients. Increased understanding of the biomechanics of flap creation and ectasia following LASIK, in addition to the dry eye and complications from manual microkeratomes led to increased use of femtosecond lasers for flap creation and a resurgence of surface ablation. Complications from LASIK, although rare, include dry eye, corneal weakness and ectasia, and questionable corneal flap adhesion. Dry eye continues to be the most cornmon complication from LASIK. Up to 37% of patients without pre-existing dry eye will be symptomatic six months after LASIK. Flap creation causes damage to corneal nerves, which may not regenerate to their preoperative level. Total disappearance of the subepthelial nerve layer at one month SIP LASIK has been reported. Prolonged recovery of corneal sub-basal nerve density after LASIK compared to PRK has also been reported. Three years after LASIK, a 34% reduction was found compared with a nearly unchanged subbasal nerve density following PRK. The reduction of corneal nerve regeneration and actual number of fibers noted in post-LASIK patients was not found in patients post-LASEK. Thus, many surgeons are increasing the amount of surface ablations to alleviate dry eye complaints postoperatively. In addition to the dry eye complications, LASIK has been found to be less stable long-term due to the severance of collagen fibers. This is illustrated by the dislocation of flaps years after surgery. The National Institute for Clinical Excellence reported the main problem with LASIK was long-term risk of 410 corneal ectasia.

Future of LASIK Surgery

- - -._--5·1

QI

~

en

1· ln

512

1105

~

Fig . 5: Visante OCT resu lts for a patient SIP LASIK with ectasia

411

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) To avoid these complications, many surgeons have turned to laser-created flaps for LASIK. Femtosecond laser planar flaps are clearly advantageous over meniscus flaps created by conventional microkeratornes. The creation of thin flaps less then 100 microns may produce less biomechanical changes and dry eye. The reliability of flap thickness makes them safer for those with thin corneas and prevention of ectasia. Wavefront ablations were found to lead to faster recovery, better uncorrected vision, and better corneal sensitivity compared to treatments using conventional microkeratomes. Unfortunately, the femtosecond lasers are expensive, enticing other surgeons to turn to surface ablations: PRK, LASEK, and Epi-LASTK. The application of wavefront to refractive surgery in conjlU1ction with improved pain management alternatives has also increased surgeons willingness to return to surface ablations. Epi-LASIK, which uses an epi-keratome to remove the epithelium along Bowman's membrane, has the advantages of LASIK and PRK without the disadvantages of either. Without a stromal flap, less higher order aberrations are induced. Patients who underwent LASEK or other surface ablations report less night vision problems including smaller starbursts, and have better contrast sensitivity then those SIP LASIK. Mild corneal opacities are easily treated using surface ablations as well. In summary, I personally do feel that surface ablations will lead the way as I do with my concept of CorneoplastiqueT M which increases the scope of refractive surgery to help refractively address even pathological corneas. Lenticular Refractive Surgery

Elective cataract surgeries with multifocal IOLs have become a great option for the baby boomers (Gulani AC: Full Spectrum refractive Surgery: FSO meeting, Naples, Florida - Aug 2006). Having personally participated in one of the First US clinical trials of Phakic implants (Gulani AC, Neumann AC. Phakic Implants 6 year follow up- ARVO, 1996) using three lens models, i.e. Anterior Baikof£, Mid-Anterior Momose and Posterior-Fyodorov lenses of four different materials in three different locations in the eye, we confirmed a predictable future for this technology. Now, with the approval of the Verisyse and Visian IOLs in the US and soon to be approved foldable phakic implants (personal communication: Gulani AC, Potgeiter F: SASCRS, Durban, South Africa- Aug 2005) we have choices for higher ammetropias and combinations like Bioptics therein. Surgeries using the entire anterior segment comprising of corneal and intraocular combinations and various permutations throughout the lifetime of a refractive candidate will finally lead the future. 412

Fuhlre of LASIK Surgery

Fig. 6: Combination surgery. Intraocular multifocal lens for previous RK-AK with high Hyperopia and Astigmatism , followed by laser surface ablation

LASIK is a surgery tha t has been around fo r nearly half a cen tury as for its concep t and technique. Wha t has changed is the technology to achieve those same goals albeit with heightened awa reness, raised expectations and of course the pursuit of Super-Vision .

413

5

E

C

T

ION

41 Refractive Management of Hyperopia Ahmad K Khalil (Egypt)

INTRODUCTION

Refractive correction o f hy peropia is often needed. Deci sion making is not a

straight forward one, because of several variables and difficulties to be tackled and several treatmen t options w ith their abilities and inabilities. CLINICAL SIGNS AND SYMPTOMS

l ow to moderate degrees of h yperopia would probably pose no serious ann oyance to the pa ti ent till his early fourties when his distance erro r becomes manifest and mo re d isabling. On the other hand, higher hyperopia errors, though not very com.m on, would usually be a nuisance at a much earlier age. Glasses correction is usually in to lerable because of the narrower field, and

increased aberratio ns associated with a powerful plus lens at glasses vertex d istance added to an already aberrated eye. INVESTIGATIONS

Biometry of the eye can be va riabl e especially in higher erro rs. Odd K-readings from mid 30s u p to early 50s ca n be seen in high hyperopes, naturally associa ted w ith various sorts o f aberratio ns . Similarly va riations in

axial length, AC depth, lens thickness can be seen. All these parameters should be known using relevant equipment as wavefront analysis and ultrasound biometry prior to planning any refractive in terference. MANAGEMENT

Several options are available for the refractive management of hyperopia; Corneal approach (Laser vision correction, thermokeratoplasty, corneal inlays), phakic 10L imp lantation (PIOl), and re fractive len s exchange (RL E) . Thermokeratoplasty including conducti ve Kera toplasty do not provide a permanent solution, and corneal inla ys are still in the experimenta l and clinical trials s tage. 416

Refractive Management of Hyperopia

Figs 1 A and B: (A) A diagram representing a cornea with a flatter central surface (oblate) , (8 ) Hyperopic laser treatment increases central cornea steepening (prolateness)

417

It/stant Clinical Diagnosis in Ophtllalmol0I5'J (Refractive SlIrgenJ)

Decision making depends on degree of hyperopia, age of the pa tient and biometry of the eye. Lower degrees of hypero pia up to + 6 wo uld usually benefit from laser vision correction. Various recent studies have s hown the

long-term stability of lase r treatment for hyperopia up to + 6 D. Lens and cornea ha ve a role to play in decision making of this group. Lenticular opacities and / or significant aberrations would direct trea tment modality away from the cornea. A steep corneal curvature (K-readings over 48.0) would similarly exclude laser v is ion correction from treatment options, as hypero pic treatment in vo lves increasing corneal prolatiol1, hence markedly further s teepening the already s teep cornea, and increasing its aberrations . VVhen lens and cornea

condition does not precl ude laser treatment, then it is probably well justified even in older populations. The increased prolation gives an added advantage

of pseudo-accommodation, which partially eliminates the dependence on near correction. When there is a cornea or lens con traind ication for laser correction,

P IOL and RLE as described below, are resorted to. Because of a hi gher incidence of regression, hyperopia over + 6D would ta ke us away from laser vision correction to lens options. PIOL (ICL or iris clip) can be warranted in yo unger populations where there is a good amount of accommodation to be preserved, otherwise RLE would be the proced ure of choice. EspeCially so, as this patient population commonly has shallower AC rendering PIOL surgery more difficult and risky. RLE becomes th e procedure of choi ce in high hyperopia w ith lost accommo dation , mod-low hyperopia; h avi ng corneal or le nticular contraindications for laser correction and / or narrow anterior chambers with

risk of closure. IOL power calculation can become very tricky with standard formulas in short globes. In eyes shorter than 20 mm, Holladay 2 or Hoffer Q give more predictable results. IOL power measurements can sometimes reach

over + 40.0D, and piggy-backing can be a necessity for emmetropia in these cases. This might be associated with an increased incidence of inte r-lenticular

opacification (ILO). The combination of 2 silicone lenses one in the bag and the o ther in the sulcus seems to be the best combination to reduce the incid ence of

lLO. Elevating the irrigation bottle height during phacoemulsification can overcome difficulties associated with a sha llow AC. PROGNOSIS

With proper choice of the modality of trea tment, refractive management of hyperopia is usuall y rewarding for both patient and surgeon.

418

Instant Clinical Diagnosis in Oplltl,almologlj (Refractive SlIrgeYlj) Decision making depends on d egree of hyp eropia, age of the patient and biometry of the eye. Lower degrees of hyperopia up to + 6 wou ld usually benefit from laser vis ion correction . Various recent studies have shown the long-term stability of laser treatmen t for hyperopia up to + 6 D. Lens and cornea have a role to p lay in decision m akin g of this group. Lenticular opacities and /o r signHicant aberra tions w ould direct treatmen t mod ali ty away fro m the cornea. A s teep cornea l curva ture (K-readin gs over 48.0) would similarly exclude Jaser v ision correction from treatment options, as hyperopic treatment involves increasing corneal prolation, hence marked ly further steepening the already steep cornea, and increasing its aberrations. When lens an d cornea condition does not precl ude laser treatment, then it is probably well jus tified even in older populatio ns. The increased prola tion gives an add ed advantage of pseudo-accommod ation, which pa rtially eliminates the depen dence on n ear correction. When there is a cornea or lens contraind ication for laser correction, PIOL an d RLE as d escri bed below, are resorted to. Beca use of a higher u1Cidence of regression, hyperopia over + 60 would take us away from laser vision correction to lens options. PIOL (IeL or iris clip) can be warranted in yo un ger populations wh ere there is a good amount of accommod ation to be preserved, otherw ise RLE would be the procedure of ch oice. Especially so, as this pa tient pop ula tion commonly has shallower AC rendering PIOL surge ry more d ifficul t a nd risky. RLE becom es the procedure of choice in h ig h hy p ero p ia w ith lost a ccomm od a tion, m od- low h yp e rop ia; ha v ing co rneal or le n t icul a r contra ind ications fo r laser correction and/ or narrow anterior chambers w ith risk of closure. IOL power calcula tion can become very tricky w ith standard formu las in short globes. In eyes shorter than 20 m m, Hollad ay 2 or Hoffer Q g ive more predictable results. lOL power m easurements can sometimes reach over + 40.00, and piggy-backing can be a necessity fo r emm etropia in these cases. This might be associated w ith an increased incidence of inte r-lenticular opacification (ILO). The combination of 2 silicone lenses one in the bag and the other in the sulcus seems to be the best combination to reduce the incidence of ILO. Elevating the irriga tion bottle heigh t durin g p hacoemulsification can overcom e d ifficulties associated with a sha llow AC. PROGNOSIS

With proper choice of the modality o f trea tment, refrac ti ve manage ment of hyperopia is us ually rewa rd ing for both patie nt and s urgeon.

418

Refractive Management of Hyperopia

Fig . 2 : Implanting a second (piggy-backing) lens in a case of high hyperopia

419

42 Restoration of Accommodation Capsular Bag Refilling

by

Okihiro Nishi, Kayo Nishi, Yutaro Nishi, Shiao Chang (Japan)

INTRODUCTION Refilling the lens capsule with an injectable material, while preserving capsular integrity including zonules and ciliary muscles, offer a potential to restore ocula r accommoda tion. The greatest technical challenge in this procedure was prima rily preventing the leakage of injectable IOLs. To prevent lea kage, we developed a silicone plug to seal the capsular opening . We could confirm someacconunodation in the young macaca monkies. Figure 3 shows the Scheimpflug pho tographies of the eye of a monkey before and after surgery, show ing evidence of some accommodation being obtained. After applica tion of 4% pilocarpine, there is thickening of the le ns with steepening of the anterio r capsule a nd shallowing of the anterior chamber, both before and after surgery, altho ugh the findin gs were much less marked after surgery. From these experiments, we ha ve concluded that refilling the lens ca psule is technically qu ite fa sible. It is suggested that the procesure may restore ocular accommodation in humans. However, there are some essential problems to overcome: Refining and sim pEfying the techn ique; Prevention of anterior caps ul e opacifica tion (ACO) and posterior ca psule opacificatio n (PCO ); Reducing surg ica Uy-induced astigmatism because the unilateral CCC, though tin y, ca used a great astigmatism (unpublished data). He re, Twill d emonstrate a comple tely new concept and novel lens refilling proced me that may solve these proble ms. We had tlus concept alread y in 1989 and resumed the technjque, because endocapsular balloon technjque and the capsular plug technique will not be supposed to be applied clinically, a nd the technjque will solve the problems mentioned above.

420

Restoratioll of Accommodatioll by Capsular Bag Refilling

Fig. 1: Schematic illustration of the tens refilling procedu re

Capsute~sea!ing

plug

" Injectable tOl

Injectable tOl: Mix of two liquid silicone compounds polymerizing in 2 h in vitro

Fig. 2: Lens refilling technique using a silicone plug (Reprinted by permission of Archives of Ophthalmology)

421

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) REFILLING THE LENS CAPSULE WITH CAPSULOTOMY-CAPTURING INTRAOCULAR LENS IOL

The rOL shape is similar to that of a conventional rOL, but the optic has small narrow grooves over its entire circumference. The CCC edge is put in this groove, which chokes the rOL, preventing leakage of the injected material. Figure 5 illustrates the procedure and Figure 6 shows the most recent foldable version of the IOL. Surgical Procedure As in conventional cataract surgerYr CCC, around 4 mm in diameter, is created

in the middle of the anterior capsule. After phacoemulsification aspiration, viscoelastics are injected into the capsular bag in the usual manner. The folded IOL is introduced entirely into the capsular bag. A Sinskey hook is introduced underneath the IOL, and the IOL is lifted by the hook, so that the optic edge groove of the lower half of the rOL is captured by the lower half of the CCc. The lower half of the groove is captured almost automatically while lifting the lower half of the rOL, because the 10L is firmly fixed in the middle by both haptics remaining in the capsular bag. Then, the viscoelastics are completely removed by aspiration, during which an 1/ A cannula is introduced underneath the upper half of the rOL, which is now outside of the capsular bag. Viscoelastics are injected into the anterior chamber onto the IOL. The upper half of the IOL is then captured by the CCC by pushing the IOL downward and posteriorly at the middle part of the IOL optic edge with a push-pull hook until the upper IOL clears the upper CCC edge to be captured. A small portion ofthe CCC edge at the optic groove is now hooked with the Sinskey hook and pulled slightly to introduce the injection cannula . The injectable material, actually a mix of two liquid silicones is then injected into the capsu lar bag. It polymerizes in 2 h in vitro.

RESULTS AND DISCUSSION

We have refilled many pig cadaver eyes and rabbit eyes using this technique. After the TOL was correctly captured by the CCC, there was no leakage of the injected silicone. Thus, the apropriate size for the CCC, not too small to capture but not too large to capture firmly the 10L, is crucial for surgical success. If the CCC is appropriately sized, the procedure is highly reproducible. We marked a 5 mm circle on the cornea using a Hoffer optic zone marker for 5 rrun, according to the technique described by Wallace, and used this mark as a guide for an appropriate CCC diameter around 4 mm.

422

Restoration of A ccommodatioll by Capsular Bag Refilling

Fig . 3: Sche impfl ug photog raphs of a mon key eye before and after refi ll ing the lens capsule. Note that there was thickening of the lens with steepening of the anterior capsule and shallowing of the ante rior chamber. After su rgery (right), there were simitar findings, though less remarkable. Note also that there were discontinuous zones in the lens before su rgery, while the refilled lens was optically empty due to the silicone compound

Anterior capsule-supported IOL for sealing /

eee

i(IO. 14mm

Nishi 0, Nishi K, Graefe's archives of clin. Exp Ophthalmology 1990

Fig . 4: Anterior capsule-supported IOL for sealing eee. The arrows show the small narrow, grooves at the optic (Reprinted by permission of Graefe's Archives of Clinical and Experimental Ophthalmology)

423

Instunt C/inicnl Diagnosis in Oplltl1almologlJ (Refractive SlIrgety) Expected Mechanism of Accommodation

The expected mechanism of accorrunodation in vo lves forward-movement of the TOL and thickening of the lens. These expected mechanisms are based on two recent stud ies. Nawa and his coworkers d emonstrated the accommodation-a mplitude obtain ed per 1 mm forward movement o f the IOL. For this purpose, a ray-focusin g equation for pseudophakic eyes was established using the ra y- traci ng method w ith dedicated compu te r softwa re. It was found that the amplitude depends on axial length and cornea l power (Table 1). [n eyes with an ax ial length of 21 mm and an IOL w ith 30 d iopte rs, 1 mm fo rwa rd moveme nt yields 2.3 0 of accommodation. Accordingly, in an eye with a length of 23 mm and 24 diopters, 1.6 0 of accommodation will be obtained, while only 0.8 0 w ill be ob tained w ith va lues of 27 mm and 11 d iopters. These fi n dings ind ica te tha t improvements may be obtained with the recen tly developed accommod ating IOL such as the Crysta lens or 1CU, specifica lly in hyperopic eyes with a short axial length. Table 1: The relationship between AL and dioptric power of an MA30BA IOL and amount of accommodation per 1.0 mm forward movement Axial Length (mm)

Paramete r

21 .0

22 .0

23.0

24. 0

25.0

26.0

27.0

IOL power (IOL)

30.0

27.0

24 .0

20.0

17.0

14.0

11.0

2.3

1.9

1.6

1.3

1.1

0 .9

0.8

Accommodati on pe r 1.0 mm forward IOL move ment (D)

(Preprinted by permission of J Cataract Refract Surg)

Van der Heijde and co-workers measu red microfluctuations of steady-state accommodation using ultrasonography, and d em onstrated that fluc tua tions in accommodation are mainly caused by fluctuations of lens th ickness. They fo und that on average, the lens increases by about 56 11m in thickness per diopter during flu ctuation. That m eans that 3 diopters could be obtained by about 0.17 mm change in thickness. Enhancement of Accommodation-Amplitude and peO-Prevention by Dual-Optic

To prevent PCO and possibly to augument accommod ation-am plitude being attained, we have drafted a dual-optic concept, as Fig. 11 shows. First, a conventional fold ab le IOL w ith sharp edges and the en hanced haptic angulation is implan ted in to the cap su lar bag. It has a concave optic with a minus diop tric power, which m ay imperatively give a greater power to the

424

Restoration of Accommodation by CapslI lar Bag Refilling

Fig . 5: Surgical lens refilling procedure using anterior capsu l e~supported IOl (Reprinted by permission of Graefe's Archives of Clinical and Experimental Ophthalmology)

Fig. 6: Anterior capsu le-su pported foldable IO l and Its dimensions

425

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) anterior optic, achieving emmetropia. During accommodation, the anterior capsule moves forward, while the posterior capsule stays relatively unmoved, so that an anterior optic with a greater power may enhance the acc-ommodationamplitude attained. A large angulation of the haptic will press the sharp optic edge against the posterior capsule to create a strong compression on it for the prevention of PCO. The injected silicone mix will additionally press the 10L on to the posterior capsule. As an alternative technique, the same CCC-capturing 10L can be implanted after a posterior CCC is performed. Then, a CCC-capturing 10L is introduced into the capsular bag which contains the 10L being implanted previously and captured by the anterior CCC, as already described. To refill the bag, silicon e mix is injected between two 10Ls that are captured by the anterior and posterior CCCs. SUMMARY

To summarize, the novel anterior capsule-supported 10L is technically quite feasible. Some accommodation might be obtained by forward-movement and thickening of the lens. We will test this procedure in primate eyes. Anterior and posterior capsule opacification at least in the optical axis can be avoided. Postoperative emmetropia is supposed to be achieved more eaSily due to the predetermined optic. One of the advantages is tha t postoperative in viva power change may be possible using an adjustable 10L. In conclusion, restoration of accommodation by refilling the lens capsule is a goal of refractive cataract surgery. Technical feasibility has been repeatedly demonstrated by obtaining some useful accommodation in primates and will be further facilitated by modern technology. Capsular opacification is one of the essential problems to be overcome. The technique shown here may provide a breakthrough for pOSSible clinical application to refilling of the lens capsule.

426

Restoratiotl of Accommodatiotl by Capsular Bag Refillitlg

Fig. 7: A well·refilled pig cadaver capsule. The anterior capsule-supported tOL was firmly fixed , and there was no leakage of the material injected

Fig. 8: A refi ll ed rabbit crystalline lens. Three weeks after su rgery. Note that the IOL was firm ly and sec urely fixed . There was no leakage of the injected silicone compound . Poste rior synechia

427

Instant Clitlica l Diagtlosis itl OphthalmologtJ (Refractive Surgery)

Fig. 9 : An enucleated rabbit lens refilled

Fig . 10: Histopathological findings of an enucleated rabbit lens refilled . T hree weeks after surgery

428

Restoratiol1 of Accomll1odatioll by Capsular Bag Refillillg

Fig. 11: Dual optic refilling concept I. The concave poste rior IOL with a minus power and sharp edges is pressed on the posterior capsu le, so that LEG migration might be prevented

Fig. 12 : Dual optic refilling concept II. The concave posterior IOL optic is captured by the posterior eee. The poste rior visual axis is expected to rema in peO-free

429

43 Custom ICLs Carlo Francesco Lovisolo (Italy)

INTRODUCTION

430

Since the celestial engineer provided the eye with two lenses, the surgical solutions to correct refractive errors may exploit tvvo anatomical objectives (by modifying the optical behavior of the cornea or the crystalline lens) or a prosthetic one (by inserting a supplementary lens inside the eye). The lifelong stable, elliptical architecture of the cornea has been designed to deliver very high vergence (more than 70% of the total focusing power of the eye), while minimizing optical aberrations. Even with highly sophisticated optimized and / or customized laser treatments, corneal procedures are subject to physical limitations and challenging complications, mostly related to the issues of wound healing and biomechanics. The optical quality of the outcomes may therefore be less than ideal when treating high ammetropias (myopia higher than 6-7 diopters, hyperopia higher than 3 diopters) and patients with large mesopic pupil sizes. Newcomer keratoplasty techniques, using tissue engineered or synthetic lenticules as refractive onlay or intrastromal inlay have, so far, only shown the potential to overcome these drawbacks. The crystalline lens gives one fourth of the power and is responsible of the autofocus mechanism of the eyes optical system. It grows and becomes sclerotic throughout life, causing changes of refraction and progressive loss of the accommodating power. The benefits of its irreversible extraction (CLE) and substitution with an artificial toric, aspheric, multifocal or accommodating implant is still controversial among eye-care providers. Accommodating IOLs ha v e so far clinically failed to solve the main complication of lens removal, presbyopia. Multifocal optics inherently decrease contrast sensitivity and require neuroadaption. Beyond the unpleasant loss of accommodation in young people, long-term safety is_a major concern for CLE, risk of influencing retinal detachment and macular pathology in eyes naturally prone to posterior segment pathology (i.e. high myopia). Instead, a supplementary intraocular lens (phakic lOLl implanted between the cornea and the lens has several theoretical advantages. It allows the crystalline lens to retain its function without risking vitreo-retinal side effects;

Custom lCLs

Figs 1 A to C: (A) Oversized ICLs may lead to ang le closure glaucoma. (6) Artist's view of the bulging of the iris diaphragm induced by the lens implant; (C) VH F echography image of an ICL-induced papillary block). Urgent lens explantation or multiple iridotomies are requ ired

431

Itrstnnt Clinical Dingnosis in OplrtlralmologrJ (Refractive SlIrgenJ)

since the quality of the implant surfaces is above the optical limits of the eye, its nod al points are nearer the pupil and the optic can be convenientl y wid e, may improve the natural properties of the eyes optical system to enhance the quality of the retinal image, allowing excellent vision even in all light conditions. It is removable and exchangea ble, permitting potential reversibility to the preoperative condition. The result is highly predictable, easily adjustable with complementary fine-tuning corneal surgeries and immediately stable, because the refractive outcome depends less on hea ling processes. The major dra wbacks of aphakic IOL surgery are essentially related to the intra-operative and early postoperative risks of a n open-eye procedure and to the long-term tolerability of the lens implant. The re is enough evidence that the dangers of an intraocular proced ure ma y be properly managed and minimized with proper care and proctoring of an accomplished surgical tea m and en VllOl1ll1ent. THE CONCEPT OF CUSTOM PHAKlC IOL

There is no doubt that the same concepts behind the universa l trend towards clistomization of cornea l refractive surgery must be immed iately applied to phakic IOL procedures. Considering the wide va riabil ity o f biological presentations, the va riety of anatomica l shapes, sizes and range of optical e rrors, the need for a custom-made lens implant w ould ap pear even more obvious than personalized corneal laser treatment. Custom-designed lenses that perfectly lit the individual anatomy o f each single eye a re obviously sa fer than conventionall y-sized ones, as late postoperatj ve complica tions relate mainly to unstable implants and less than ideal dista nces from the internal structures. Once inside the eye and over time, w ithout a perfect fit, each site of haptic fi xation has its own area of unique concern and accurate preoperative assessment of the lens im plant-to-tissue clearances becomes vital to avoid safety concerns. Angle-fixated and iri s-supported 10Ls may induce acute and recurrent subchronic iritis, ischemic subatrophy of the iris, pupil distortion, progressive endothelial cell loss, secondary glaucoma, and breakage of the blood / aqueous barrier with persiste nt aqueous flare and cystoid nlacular edema. When too long, posterior chamber phakic, like the Visian ICU " (Staa r, Monrovia, CA, USA), excessively vau lted between the iris posterior pigmented laye rs and the anterior crysta lline lens, may cause the iris diaphragm to bulge forwa rd, w ith narrowing of the irido-corneal ang le, chafing of the poste rior iris surface, pig ment dispe rsion and subsequent risk of angle closure and pigmentary g laucoma, ocular pain or tenderness due to nerve irritat ion by excessive 432 pressure in the Ciliary sulcus, cyclitis and macular edema. On the other hand,

Custom lCLs

Figs 2A to C: (A) Artists view; (B) Scheimpflug camera and (C) Slit lamp images of typical iatrogenic anterior subcapsular opacities of the crystalline lens caused by the lack of vaulting of an undersized ICL

433

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) lack of vaulting because of short has caused iatrogenic anterior subcapsular cataract by preventing the nutritional turnover on the lens surface and implant decentration. We should be aware that the vast majority of these iatrogenic damages to the delicate inner structures depend on human errors: the wrong selection of an unwelcome intraocular enVir0111nent or the wrong choice of the overall length of the implant. Custom sizing the Overall Length

C .. the choice of the implant overall length appears particularly critical .... Unfortunately, proper measurements of the inner diameters are not achievable by any means .. " at

Since the prophetic words of Benedetto Strampelli of the early 1950s

the Societ" Oftalmologica Lombarda, December 1953) proper sizing h as been considered for decades the 'mission impossible to optimize safety of phakic IOL surgery. Anachronistically, after more than half a centu ry and despite the lack of scientific proof behind it, the vast majority of surgeons worldwide sti ll behave like him, selecting the overall diameter of the lCL according to the 'golden rule of thumb, by empirically adding 0.5-1.0 mm to the horizontal corneal diameter (white-to-white di stance, W-to-W) obtained externally. Wh ether measured at the slit lamp by comparison with a ruler or gauge, or under the operating microscope using the surgical caliper, white-to-white is an unreliable landmark, as the points where white begins and gray starts at the limbus are open to each surgeons personal interpretation. More standardized strategies, based on the analysis of digital photographs from video-keratography or laser partial coherence interferometry images-have sli ghtly improved the precision achieving acceptable reprodu c ibility tolerances. Nevertheless, numerous findings from in vivo ultrasound and MRl studies, anatomic observations on cadaver eyes have definitely showed that, regardless of the accuracy of the Ineasure ment of W-to-W, there is no proportional anatomical correspondence between external measurements and internal dimensions of the anterior segment compartment. Internal anatomy cannot be predicted by external measurements. As a consequence, W-to- W distance alone is totally adequate for sizing lCL. Instead, the exact internal linear sulcu s-to-sulcu s (5-to-5) distance, the iris-to-crystalline lens relationship (distance between the iris and the ciliary processes, w idth of the irido-corneal angle and of the iris-crystalline angle) - m easured point-by-point at different levels, should be used. Accurate imaging of these hidden anatomical sites can be obtained with high-resolution ultrasound devices that use very high frequency (VHF) waves in the 35-to-50 MHz range, like the Artemis 2 (Ultralink;-St. Petersburg, FL, USA) and the Vu-Max (Sonomed, New York, NY, USA). Optical devices like slit scanning systems with or without rotating Scheimpflug camera (like the Precisio, Ligi, Taranto, italy, the Pentacam,

434

Custom ICLs

Figs 3A to C: (A) In a series of 200 patients where the W·to-W distance was accurate ly measu red with the Orbscan and the 'golden rule' (W-to-W + 0.5 mm = overall length) meticu lously applied, we achieved the desi red outcome (vault height between 200 and 700 microns) in 59% of cases (8 ); in 24% of cases we got sign ificant Qvervault, superior than 700 micron s; and (C)

and in 17% an insufficient vault, inferior than 100 micron

435

Illstallt Clillical Diagnosis ill OplrthallllologtJ (Refractive Su rgery)

Oculus, Germany and the Galilei, Ziemer, Germany), or infrared ligh t optical coherence tomography sys tems (OCT Visante®, Ze iss-M editec, Jena, Germany) permit high-resolution cross-sectional anterior segment imaging w ith excellent reproducibility of mea surements by using the interference profile of the reflections from the cornea, the iris and the crystalline lens. These methods are not interesting for sizing the ICL, since the retro-irideal space cannot be perfectly visualized by optical devices and the sta tistical correlation between angle and sulcus diameters is as poor as between external w hite-to-white and internal d imensions. On the basis of our experience, started more than 13 years ago (September 1993), the ideal central vault height for a n lCL is conside red to be around 350 J.lm in m yopic and 250 J.lm in hyperopic implants, to provide safe separa tion from the anterior surface of the crystalline lens and minimize untoward effects on aq ueous hydrodynamics. H yperopic can have a lower va ult than their myopic cou nterparts beca use the peripheral geometry of positi ve lenses leaves more space in the pe riphery to the ci rculation of nutrients and hype ropic eyes tend to have shallower chambers with narrower angles. For myopic implants, a minimum mid-peripheral clearance of 150 pm is require d. When we observ e lower or mechani ca l contact, leL explantation and / or exchange with a larger overall size should be considered for the hjgh risk of iatrogenic cataract. Since 1997, we have been using a modified trigonome tric formula to predict vault height precisely. The va riables entered into the formu la included the sulcus-to-sulcus distance, as measured with the lABDTM(Innova tive Inc, Canada), and the radius of curvature of the anterior surface of the crystalline lens (obtained with the EAS 100QTMScheim pflug camera, NlDEK, Tokyo, Japan). The constants in the formula included the elasticity (elongation factor) of the colla mer and the base-curve of the ICL. Since then, we have improved the formula and now are using a proprietary software to simulate the expected clearances between corneal endothelium, iris and crystalline lens. The last LOVISOLO ICL S/ZER® software takes into consideration: • The three-dimensiona l map of the biome tric data of the patients anterior segment as obtained from VHF ultrasonography (Artemis 2 or VuMax scans);

436

• The specific features of the chosen lens implant (overall length, vault, central and peripheral optic thickness, flexibility); a corrective factor, considering the va riation of ICL dimension from the labelled size (as measured in vitro at 20°C) when going into the aqueous envi ronment. Intraocularly, for instance, a 125V4 ICL enlarges from 12.5 to 13.2 mm; • Its behavior und er compression, as predicted by finite element analysis; • The age and the life expectancy of the patient. As the human lens grad uall y grows, doublulg its thickness and displacing anteriorly by 0.4 rnm during the lifetime of a 90-year-old, due to the li fe-long mitotic activity of the sub-

ClIstOIll I CLs

Precisio -~-

..........

T

N

S

Dr i..• .

Close

--

Figs 4A and B: Bidimensional maps (A) and cross-sectional scan (8) of the anterior chamber provided by the precisio rotating Scheimpflug camera (UGI, Taranto , Italy); authors left eye OCT Visante image

437

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) capsular epithelial cells at the lens equator, the anterior chamber depth drops by 0.75 mm over a 50-year span. An average red ucbon olthe anterior chamber depth of 0.015 mm per year is calculated to predict the anatomic relationships even after 50 years; • New anatomical safety parameters are introduced (Table 1); a warning signal if more than one parameter shows a difference higher than 20% from normal value. In our most recent personal series on 394 eyes implanted with the TCL V4, after a maximum follow-up of almost 9 years (since April 1998) and a mean follow-up of 39 months, we have not yet observed any cases of iatrogenic cataract, pigmentary dispersion or angle closure glaucoma. The mean central vault height was 386 flm, with a standard deviation of ± 113 )lm. The minimum vault obtained was 189 flm. In the 95% confidence interval, an expected vs. achieved vault height in the ± 150 )lm range was obtained in the 95% confidence interval. In comparison with the group control of 237 eyes, where the ICL was implanted on the basis of the W-to-W, the mean central vault height was 406 mm (not statistically significant), but the standard deviation was highly significant (± 667 )lm). The minimum vault achieved was 0 mm and the incidence of size-related compli cations (angle closure glaucoma, cataract and clinically significant pigmentary dispersion) was around 8%. The reference point of the 95% confidence interval as referred to the expected vs. achieved vault height was reached for the range of ± 730 )lm. For further comparison, the reader should know that similar values could be easily obtained from multivariate regression analysis by sizing the ICL on the basis of anterior chamber depth, corneal pachymetry, opening of the iridocorneal angle, angle-to-angle distance, axial length, but also shoe, hat, or glove size! While recognizing that researchers are still far from fully understand the de tailed mechanisms of ICL-induced cataract formation, we attribute these results to the meticulous selection of the anatomic features of each single eye and to the precise sizing of the implanted lenses, allowing an ideal prediction of lens vaulting. With the extraordinary confidence the system provides to our practice, we now consider as relative contraindications and evaluate on a case-by-case analysis many of the conditions that have been considered exclusion criteria

Crystalline lens rise over the iris plan (cycloplegia): 0.4 mm Iris configuration (sclera-iris angle): 28.1 " Ciliary body position (sclero-ciliary angle) : 53.1 " Irido-Corneal Angle: 31.3" Crystalline lens anterior curvature: = 12.08 mm (cycloplegia)

- R

438

R

= 10.3

mm (non-accommodating miosis)

Custom lCLs

Figs 5A and B: The first generation of the Lovisoto te l Sizer® software. As the ultrasound cone width was lim ited to 8 mm, two scan images were pasted together to measu re the sulcus diameter (from left and right ciliary recesses to the geometrical center of the crystalli ne lens) and the anterior curvatu re of the crystalline lens was measured (A and B) then the trigonometric Fumagalli sag formu la was applied

Figs 6A and B: Snapshots of the second (A) and last (8 ) generation of the Lovisolo tel Sizer®. In B a predicted versus obtained vault is shown

439

Instant Clinical Diagnosis in Ophthalmology (Refractive SlIrgenj)

(Table 2). Pediatric age, for instance, is not an absolute preclusion to surgery any more. An original excess of caution made it wise to avoid implanting phakic in children, but special cases of unilateral ammetropia or hi gh anisometropia with contact lens intolerance and functional strabismus are worth reassessing, to prevent amblyopia. Old absolute contraindications ha ve now proved too conservative, like in the case of stable ectatic corneal disorders (keratoconus, pellucid marginal degeneration, iatrogenic ectasia) and sequelae from trauma, infection or unsatisfactory previous corneal surgeries (like PKP, LKP, RK, ALK, epikeratoplasty, LTK, PRK, LASIK) that may be dealt with successful outcomes. Eyes with anterior chamber depth (ACO, endothelium to anterior crystalline central distance) less than 2.8 mm can also be implanted with an excellent safety ratio. Although still a preclusive medico-legal reference point, a single measurement of the central ACD, usually obtained by conventional A-scan ultrasound biometry, cannot help in preventing angle closure glaucoma after ICL surgery if no information is provided on the opening of the irido-corneal angle, the shape of the anterior segment, the crystalline lens rise over the pupil plane. No complication was encountered in a series 61 eyes, where the ACO was lower than 2.8 mm, but the other parameters were considered safe. Eyes w ith endothelial cell count lower than 2000 cell s/mm (postkeratoplasty ammetropias for instance are excellent candidates) may safely undergo ICL surgery as the iris_-barrier between the ICL and the cornea protects against corneal decompensation. Our long-term (based on more than 10 years of maximum follow-up) cell losses are completely similar to physiological decay (0.6% per year). Moreover, in the retrospective analysis of our last 6 years series, we observed that no intraoperative endothelial cell sacrifice is required any more. The mean postoperative ceUloss was 0.4%, with as much as 46% of eyes whose count and morphometric indices improved . Apart from some unavoidable endotelioscopy bias, these apparently paradoxical findings are probably due to the postoperative tiiifYf';:;~ Table 2: Generally accepted inclusion criteria (Safety guidelines) :"" ",",;//"

for phakic IOL surgery Age> 21 years Stable ammetropia, not amenable to excimer laser surgery Intolerance of contact lenses or spectacles Centra! ACD ';:;>: 2.8 mm Irido-corneal angle aperture,;:;>: 300 Endothelial cell count> 2,000 cells/m m2 Overall length based on external White-to-White distance No previous ocu lar surgery No ocular pathology (glaucoma, uveitis, cataract, etc.)

440

No systemic diseases (diabetes, autoimmune disorders, etc.)

:5>

":'r

~;"" ,~

Custom ICLs

-_ _.) ...-------------------....., .

Figs

7A

and

B:

AnsysTM finite element

analysis

(A)

and

mechan ic al compression data (8 ) were compared to get the intraocular behavior

of every lens

441

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery)

centrifugal migration of peripheral endothelial cells and to the cell enhanced metabolism after stopping contact lens wear. Using VHF echotomography (Artemis 2) and scann ing s lit optical tomography (Orbscan II) we realize that there is no precise correlation between central and peripheral depths of the anterior chamber (Sizing Phakic, presented by Lovisolo CF at the ASCRS meeting, San Francisco, April 2003). A certain number of eyes show a progressive narrowing fro m center to periphery, with the nasal regions about 20% shallower than the temporal counterparts. However, some are strangely shallower in the center and each single eye seems to have its own anterior chamber shape and volume, w ith no general rule. In a sample of288 eyes scanned with VHF Echography, the largest

cross-sectional internal sulcus diameters was found horizontally in 27%, obliquely in 15%, vertically in 58% of cases. The largest external diameter (white-to-white) was found to be horizontal in 100% of cases. W-to-W was found larger than S-to-S in 59%, the opposite was found in 41% of eyes examirted.

As regarding efficacy and functional performance, the same concerns abou t the quality of vision in kerato-refractive surgery apply equally to phakic. To prevent the symptoms of the 'GASH-tetrad syndrome (glare, arcs, starbursts, halos), the customized optic would ha ve: J. The necessary sphero -cylinder power. Like in second a ry IOL implantation in aphakic eyes, or piggy-back pseudophakic implantation, the power of an [CL positioned intraocularly is equivalent to the power of the lens measured at a given distance from the corneal vertex. It is not

necessary to determine the axial length, the crys talline lens thickness and the vitreous chan1ber length, as they remain completely unchanged. This calculation depends very much on precise refractive measurements,

442

but also on the ability to predict the intraocular position of the nodal points of the lens (ELP or Effective Lens Position, the distance between the secondary principal plane of the cornea and the principal plane of the lOLl to avoid over or undercorrection. Currently ava ilable refined tori c lens implantation requires an astigmatically neutral surgical incision and robust fixation site to provide rotational stability over time. For that reason the 6-to-7 mm opening of the eye needed for in1planting the Artisan PMMA lens seems too challenging for the average surgeon, while the rninin1al size (2.5 rnm) achievable with the ICL seems ideal. The rotational stability of the toric ICL is even more important, as the cylinder correction decreases with increasing deviation of the lens implant from the target axis by following a non-linear relationship. As shown in a stud y where the positions of a g roup of s ized w ith VHF echography we re docum ented by superimposable slit-lamp photographs (Carlo Lovisolo, unpublished da ta), the mean lens deviation from the original meridian over time

Custom lCLs

Fig. 8: A toric tel was implanted three months after a couple of intrastromal corneal ring segments ( INTACS) we re inserted in an advanced stage case of pe llucid marg ina l degenerat i on . Preoperative ly, the BSCVA was 20/80 with -13 .00 -12.00 x 1 t5°; after INTACS implan· tation BSCVA was 20/30 with -11 .25 -6.75 x 98°; 6 months after teL

surgery UCVA was 20/ 20!

Figs 9A and B: As can be seen from the two Orbscan maps (A and 8 ), similar peripheral

narrowing of the anterior chamber (depths equal to about 1.9 mm at 3 mm of eccentricity) corresponds to completely different shapes and volumes of the ante rior segment [(central depth 01 3.8 mm in (A) 2.6 mm in (B)I

443

Instant Clinical Diagnosis in Ophtl/almologtj (R efractive 5l1rgenj)

444

(three years) is less than 5°, i.e. compati ble with a maximu m of 10% loss of as tigmatic correction. Once aga in, as small implants may rotate, accurate sizing is mandatory. II An effective d iameter at least as large as the mesopic entrance pu pil diameter. Infrared pupillometry has shown that scotopic pupil d iameter in young m yopic patients - the average candidates to ICL surgery - is signilicantly larger than in the emmetropic group. Our observations on more than 3,000 Caucasians m yopic eyes, ranging from 21 to 39 years of age, showed a mean scotopic pupil diameter of 6.87 ±0.72 mm, the range of minimum-maximum value going fro m 5.6 to 8.9 mm. For that reason, d ue to the limited diameter of the optica l zone, all currently available phakic have been reported to induce diiferent degrees of night time visual disturbances (mainly halos and g lare when dri ving ve hicles). The successful trend of combining different surgical approaches (Bioptics and / or Adjustable Refracti ve Surgery) has highlighted not orily the concept of fine-turting residual refracti ve errors after implantation but also the need for a wide functional optical zone. For a -1 7.00 correction in a patient with a 6.0-mm meso pic pu pillary diameter, for ins tance, postoperative quality of vision is unquestionably better if we select a Wide-optic implant (a -12.00 lCL has a 5.5-mm diameter and corrects approxima tely -10.00), and combine it with a -7.00, 6.0-mm optical zone excimer laser ablation, instead of implanting a -20.00, 4.65-mm optic ICL, fully correcting the -17.00 dt ammetropia. As a trend, taking advantage of new designs and higher index materials, it is easy to foresee that the average effective optical zone of futu re lenses will soon be made larger; III. A proper geometric shape factor (asphericity) to respect physiology. Conventional high-power (more than - 12.0 and + 7.0 0 of correction) spherical phakic with an average optic size of about 5.0 mm inevitably induce moderate amounts of spherical aberration and coma, thus red ucing contrast sensitivity and increasing glare and halos for the ave rage mesopic p upil. An aspheric phakic lens can be designed on the basis of theoretical assumptions (to li mit spherical abe rration without reducing the depth of focus), or wavefront analysis from aberrometers (to correct not only on-axis aberrati ons like spherical aberration, but also higher-order aberrations like trefoil and coma). The weak point of aspheric lenses is the need for perfect aligrunent with the cornea and crystalline lens (centration and tilt). When measured as a mod ulation transfer function, the optical performance of an aspheric IOL is not degraded if the IOL is decentered less than 0.4 mm and tilted less than 7°. Larger discrepancies between lens optical center and visual pathway could cause Significant symptoms. Our observa tions with infrared photography and VHF echography on a group of patients implanted with d ifferent phakic

Custom ICLs

Figs 10A to C: Artemis 2 (Ultralink) images of external, white-la-white (W-to- W) and internal measurements, angle 10-angle (A-IO -A) and sulcus -ta-sulcus ( S-foS) distances, relevant for sizing ICLs. Without a statistical correlation or a rule , some eyes show almost identical Ata -A and S-to-S distances (A); in the majority of cases A-toA is larger than S-Io-S (6), in the minority the opposite is true (C)

Figs 11A to C: VuMax (Sonomed) VHF echography images of a perfectly sized teric Visian lCL with a central vaulting of 355 microns (A) and retroirideal details of haptic positioning in the ciliary sulcus (8 and C)

445

In stant Clinical Diagnosis in Ophthalmologtj (Refractive SlIrgenj)

showed that pupil decentration is 0.32 nun and tUtisSo on average (Carlo Lovisolo, unpublished data). H owever, in patients with largely positive angle kappa , even an accurate sizing co uld cause a s ign ificant misalignment with the line of sight. Once this becomes more accurate and standardized, we can foresee a demand even for haptic customization, wit h asy mm etri cal loops and wings to match individual pupil decentration. Otherwise iris-fixated lenses that can be nicely centered over the pupil will be preferred to sulcus-supported lenses. N. quality of the surfaces higher than the eyes optical limi ts, possibly designed on the basis of wavefront detection. Custom ICL could be therefore indicated in piggybacking pseudophakic eyes w ith Significant residual ammetropia, as well as in pediatric patients with aniridia, albinism, anisometropic amblyopia or in eyes with naturally occurring or iatrogenic, stable corneal disorders (keratoconus, marginal pellucid degenera tion, post-RK h ype ropic shift, pos t-LASIK iatrogenic keratec tasia, post-trauma or post-keratoplasty astigmatism ... ), which cause significant higher-order aberrations and may theoretically be tackled by making the compensa ting corrections intraocularly instead of on the corneal surface. CONCLUSIONS

We can roughly estimate that around 100,000 phakic have been implanted to date throughout the world. Many surgeons worldwide actually share my opinion that, so far, the Visian-ICL is the winner of every competitive analysis of the products available on the market. Its collamer material offers the best biocompatibility; the surgeon's learning curve and experience in sorting out intraoperative difficulties is not as steep as for other models; its fo ldability aLlows minimally invasive, smooth insertions as well as safe removals under topical anesthesia and through anastigmatic small incision, with absolu te patient comfort and the fas test rehab ilitation amo ng anterior segment procedures; it prod uces excellent results in terms of precision, pred ictability (the percentage of eyes obtaining ± 1.00 0 from the desired refraction is 100%), and stability of the refractive outcome; a toric optic may correct high degree of astigmatism with unbelievable outcomes in 'desperate cases; the iris-barrier protects against the most feared complication of phakic IOLs, progressive endothelial cell loss; the incidence of catastrophic events like endophthalmitis and retinal detachment (only anecd otal reports) is accep tably low; provided that a perfect lens sizing guarantees a smooth, wuform distribution of mit1imal pressures at the fixating points without lOSing intraocular stability, the long term risk/ benefit ratio is more than acceptable, as late comp li ca tions, iatrogenic cataract in particular, are mainly due to hwnan errors in sizing, so 446 they can be expected to become less frequent as surgeons gain experience.

ClIstom lCLs The absence of synechiae and chronic inflammatory p henomena encapsulating the haptics will facilitate future implant exchange or the 'bilensectomy, procedure w hen the time comes for cataract surgery in these subjects. The reported nighttime visual symptoms (halos, arcs and gla re) are d isabw1g only in a minority of cases and are destined to become minor issues with the latest and fu ture generations of wide-optic customized lenses. SU1Ce the im plant is generally inserted into pristine, young patients eyes, the ethical endeavor to ensure a li fe lon g enduring ha rmonious relationship w ith the internal structures is mandatory. Only a Cus tom ICL, perfectly designed on the u1dividual ana tomic and optical features of each single eye may accomplish all these goals. At last, after almost a decade of sterile d ebate, I sincerely hope that times are mature to:

• Abandon empirical technique, like the 'junk White-to-White based state of the art sizing method; • Perform the most crucial choice (size the overall length of the [CL) on the ba sis of anatomically corre lated measurements, obtained with the newest high resolution biome try devices (VHF Echography) and calculated by an accomplished soft ware; • ask the firm marketing the ICL to provid e at least the intermediate sizes (0.25 mm s teps) and a wid er range (from 11 to 14 mrn) of lens diameters; • Closely monitor the [CL implant-to-tissue clearances yearly, w ith the same High-Res instruments and decide fo r prompt removal! exchange if vault height values are outsid e the safety limits.

447

44 Mini Incision lOt ImplantationCurrent Scenario Roberto Bellucci, Simonetta Morselli (Italy)

Mini incision 10L implantation has many features different from standard 3.2 mm incision 10L implantation. The main differences are in the 10L design and material, in the cartridge and plunger design and material, and in the injection teclmique. As a rule, current three-piece hydrophobic 10 Ls are not suitable for sub 2.5 mm implantation, because of the possible damage of the loops or of the loop attachments when forced through the 1.6-1.8 mm intemal lumen of a mini incision cartridge. Among the single-piece 10L we should consider: • 10Ls that have been developed to be implanted th rough mini incision • 10Ls already developed for 3.2 mm incisions, that can be implanted through mini incision. MINI-INCISION 10LS

Mini-incision [OLs are d efined as the TOLs that have been conceived and designed to be implanted through 1.6-1.8 mm internal d iameter cartrid ges. Therefore, they need to have reduced volume and diameter when folded. To do so, they could be thinner than regular 10Ls, smaller in optic diameter, and with some optical features allowing add itional thickness reduction. ote that the leng th of the 10L is no t an issue w hen conSid ering mini incision implantation. As for the material, the properties required for mini incision 10Ls are favo u ring hydrophilic acrylic materials with high water content. Most of currently used polymers seem suitable to construct mini incision 10Ls, and several Single-piece hydrophilic acrylic 10Ls are appea ring. There a re several elements that favour mini incision 10L design. Among them the d esigners and the prod ucers select the combination that seem s the best option to obtain an ]OL with the same optical and mechanical properties as the 3.2 mm incision ]OLs. So far, the results ha ve been encouraging, but we are only close to the solution of this problem. Mini Incision 10L Design Thickness

The basic thickness of the 10L can be red uced simply by designing a thinner optic border. However, several problems cOl~ d arise when doing so. The thinner 448 border cou ld prevent posterior capsule opacification by Elschni g pearls

Mini Incision IOL Impiatltation-Current Scenario

Fig . 1: A three-piece IOL of the currently available designs cannot be delivered through a mini incision cartridge of reduced size

Figs 2A and B: T hin IOLs are commonly produced in a 4-haptic design to ensure stability inside the capsular bag

449

Instant Clinical Diagnosis in OphthalmologJ) (Refra ctive SlI rgert)) formation at a lower extent than a thicker border, an issue d irectly related with the edge curvatu re radius. In addition, the position and the stability of the IOL inside the eye could be affected by the position and movement of the vitreous body, thus g iving rise to pseud ophakic refractive inaccuracies and / or to refractive variations. The possibility is to increase pseudoaccommodation, the risk is to randomLy reduce distance vision. Moreover, any uneven pressure on the posterior optic surface or any loop compression at bag equator could produce optic tilt or loca lized displacement, increasing the resulting optical aberrations. For these reasons new thin IOLs show newly designed four loop haptic, that favo ur IOL stability inside the eye with good res ulting optical quality. Optic Diameter

The reduction of the optic d iameter from 6 to 5.5 mrn or even to 5 rnm can be a further way to IOL volume reduction, either maintaining an overall optic diameter of 6 mm or reducing it to 5.5 or to 5 rnm. PMMA IOLs of 5.5 rnm optic diameter have been extensively used in the past, with no complication about postoperative vision. With these IOLs, the problems could be related with the capsulorhexis d iameter, that could be difficult to center over the IOL optic border, and with the loop length and stability. IOL displacement due to capsular shrinkage, unwa nted refraction inaccuracies and pseudo accommodation could be an issue with these thin and small optic IOLs. Op tic Properties

450

There are ad d itional methods to reduce the optic thickness. The use of Fresnel optics has been implemented in intraocular lenses, with the app roach to use an entirely Fresnel lens, or to combine a center refractive and a peripheral Fresnel optic. This second ap proach has been used in clinka l prac tice, leading to a big reduc tion in lens thickness and allowing a 6 rnm optic implantation through a 1.5 mm incision. However an d despite the good visual acuity, the optical quality as measured by aberrometers and the quality of vision as judged by patients have not been completely satisfying, so tha t this approach has been almost aba ndoned. A second method to red uce center thickness while mainta ining the same border thickness is to implement an aspheriC design on one or on both optic surfaces. EspeCially with high positive lenses, the aspheric design is much fla tter than the spherical design, and this fl attening can give ri se to a thicker border, or it ca n be used to reduce the IOL center thickness. A third way towa rd s thinner IOLs while maintaini.ng thick borders is the use of high refractive index (RI) materials. Current hydrophilic and hydrophobiC acrylic materia ls have RI between 1.43-1.46, and only one well proven material has a RI of 1.55. [n the past, hydrophobiChigh RI IOLs have been observed to give rise to mo re dysphotopsias than other IOLs, and some imp rovement in

Mini Incision IOL Implantation-Current Scen ario Paraluex anterior and-+ poslerior surface Third posterior optical surface _ Second posterior surface ____ So micron night ....... Apex Central surface _ /

Central axis Lach posterior has of save focal point

Fresnel lens 1a

Ught rays

Refractive lens 1b

Figs 3A to C: The combination of a center refractive and of a peripheral Fresnel optic allows great thickness reduction as compared with conventional design (dotted line)

451

Instant Clinical Diagnosis in Oplttll alm ologtJ (Refractive Sllrgery) IOL design was necessary to solve this problem. Therefore, any design considering high RI should take into account the necessity of steep anterior curvatures, that could reduce the advantages of this material for small incision IOLs. IOLs that can Fit Mini Incision Some of the properties of IOLs designed for mini incision can be found in IOLs designed for 3.2 mm incision. For example, the combination of aspheric design to reduce central thickness, high refractive index and 5.5 mm optic diameter allow the single piece Acrysof IQ to pass through a reduced size cartridge. A few currently available 6 mm optic IOLs can be implanted through incisions that are 2 to 2.5 mm wide, provided they are properly loaded and provided they have some additional properties favourin g the passage through the cartridge and the unfolding inside the eye. As the cartridge is hydrophobic, the contact with an hydrophobic IOL could generate mo re friction than with an h ydrophilic IOL. Therefore, h ydrophilic IOLscould be preferred in this respect. Among hydrophilic IOLs, specific surface characters can be of help during injection. For example, the limited duration of the polishing p rocess is of great importance in obtaining square edges and smooth surfaces. An additional reason to prefer hydrophilic IOLs is their ability to express some water when compressed, thus showing some adaptation to small cartridges. When the ca rtridge is very small, the plunger calUlot reach the cartridge tip without breaking it. Therefore, the plunger can only initiate the lens delivery, that should continue and be completed automatically once sta rted. The elastic force of the lOL, aiming at restoring its original form once folded, is of outmost importance in this respect. If the lens has great elastic force, like with silicone or some hydrophilic acrylic materials, this force will extract the lens from the cartridge tip without need of pushing force from the plunger. If this elastic force is low, like with some hydrophobic acryliC materials, then it is necessary for the plunger to complete its action by reaching the cartridge mouth. Mini Incision Cartridges

452

Although the perfect solution for small incision cartridges is still lacking, there are some features for the cartridges to allow injections through sub 2.5 mm incisions. The main character is the width of the internal lumen, that should be 1.6-1.8 mm in diameter to allow 1.8-2.2 mm of external diameter. The inner diameter is in relation with the ability of the IOL to be compressed to the required dimensions. The outer diameter is in relation with the incision width. The thickness of the cartridge wall is in relation with the abil ity of the cartridge not to enlarge itself while IOL d elivering, that could impair the actual size, stretch the incision and even cause cartridge rupture. For this reason, there is the need for thinner but stiffer walls.

Mini l ucision IOL Implantation-Curren t Scenario

Fig. 4A : The 6 mm optic IOL must be loaded with the haptic outside the optic to fit a mini incision cartridge

Fig. 48: The elastic force of the IOL favours unfolding and can extract the IOL out of the mini cartridge even if the plunger will not reach the mini cartridge opening to avoid cartridge rupture

453

Instant Clinica l Diagnosis in Opll tlwlll1ologtj (Refractiv e SlIrgenj)

The cartridge tip design should favour the entrance through small incisions. Short cuts on both sides of the cartridge tip can allow the tip itself to close to smaller dimensions and to enter more easil y through a mini incision. However,

with this design the tip itself m ust enter the incision to prevent the lens fro m opening outside the eye. Uncut tips can be only applied to the incision without entering it. It is the lens that opens the incision lips and enters the anterior chamber, that saves the space occupied by the cartridge wall. With this injection method, however, some counter pressure must be exerted to prevent the lens from opening outside the eye. This counter pressure is obtained by pulling the eye towards the cartridge by means of an inst rument inserted through the side port incision. A drawbac k of this method is the frequent Joss of viscoeJastic material from the anterior chamber, with poor visibility, more difficuJty of the maneu ve r and increased risk of damage. With small incision cartridges, the plunger can be a problem. A stiff plunger may not adapt to the wide Jumen at Jens folding and to the narrow lumen at lens delivery. If too thick, it will not adap t to the cartridge tip, w ith risk of ca rtridge rup ture. If too thin, it w ill en trap a lens haptic with possible hap tic damage or rup ture. The solution found in practice is a grooved p lunger, that can be compressed through a very small tip, or a very soft one, that can adap t to various diameters. Even a viscoelastic plunger has been found effective and entered some clinical practice.

454

Mini Incision IOL Implantation-Current Scenario

Fig. SA: The compressed IOL can enlarge the mini cartridge during implantation, with possible cartridge rupture or IOL damage

Fig . 58: The mini cartridge tip can only be applied to the mini incision without penetrating, and only the IOL enters the eye

455

45 Monofocal HOA Free IOL to Correct Secondary Presby-LASIK Frederic Hehn (France)

INTRODUCTION

Presby-LASIK in phakic eyes has got now a world wide acceptance among ophthalmologist's community. In my experience it's possible to compensate presbyopia, in monofocal pseudophakic eye. CLE (clear lens extraction) and RLE (refractive lens extraction) become more and more popular with the newest relracti ve-diffractive Mu lti foca l IOL. But there are some medical risks with CLE, and the results 01 MF IOL are not always as good as it would have been expected. Then some surgeons propose a wavelront lasik enhancement, after MF IOL. Because there is some residual ametropia~ astigmatism or halos. We don't think that a bioptic could be better than a primary presby-LASIK. It w ill be always better to modified only one lens of the eye (cornea) rather than two (cornea and crystalline lenses). With the both phakic or pseudophakic eye we preler a presby-LASIK technique. Presby-LASIK in pseudophakic eye make sense to proof the truthfu~,ess of the optical basement 01 this technique; and consequently the durability of the results in phakic patients. In this article we analyze the relationship between Q value asphericity and the amount of spherical aberrations. We observe what's happen during accommodation; propose 3 shapes 01 corneal presbyopia compensation, and finall y give some exa mples with topolink treatments. PRESBY-LASIK IN MONOFOCAL PSEUDOPHAKIC EYE

Presby-LASIK could logically compen sate presbyopia in emmetropic pseudoph akic eyes w ith monofocal IOL (intraocular len s), as the M F (multilocal) TOL does. The centered presby-lasik technique with distant vision in the center can give a very good distant vision and a useful optional near and intermediate vision. Natural eye is a bi-optic optical system with a variable axial myopic additional power due to the crystalline lens. Because evidently along visual axis (object to macula) the vision will be the more discriminate with the best contrast sensitivity and MTF (modulation of transfer function) for the both near and far vision. This bioptic system produces the best near and distant 456 visual acuityr in using crystalline lens accommodation which can be achieve.

Monofoeal HOA Free IOL to Correct Secondary Presby-LASlK

Visual axis

~ ~

Retina Cornea Fig. 1: Coma

Ps eudophakic monofocal = DV

Pupil

Fig . 2

Increasing MF cornea jv-+nv

Fig. 3

Figs 2 and 3: Corneal multifocality can give inte rmediate and near vision in pseudophakic

eyes

457

Illstallt Clill ical Diagnosis in Opilti1almologtJ (Refractive Surgery)

Because Presby-LASIK can not restore accommodation, it just can be a good compromise between near and distan t vision. Natu ral eye present some coma HOA due to the difference between visual axis (object to macula) and optical axis (a pex of cornea to the center of crystalline lens). Tha t's the reason why we are thinking that presby LASIK teclm ique does not increase the natural existent coma. Then to avoid to increase conla presby-LASIK must be centered. Insp ired of multifocal or bifocal soft lens for presbyopia, tha t's give good resul ts in many cases, the therapeutic choice will be to place distant vision in center or not. Some authors have got good results with a small optica l zone for near vision in the the very center cornea. INTEREST OF USING AN IOL HOA FREE TO CORRECT PRESBYOPIA IN PSEUDOPHAKIC EYE

If we are using the BandL akreos adapt IOL, Q value of this IOL is -0.55 then it creates no SA. Therefore the crystalline implantation does not modify the corneal rebuilt shaping for presbyopia compensation. A pseudophakic eye with this kind of IOL, give us a pure human corneal model, to well understand what exactly presby-LASIK does. Secondly Presby-LASIK in pseudophakic eye make sense to proof the truthfulness of the optical basement of this techni gue; and consequently the d urability of the results in phakic patients. And we are thinking that: when our patients would have been cataract surgery, they would keep the results of their previous presby-LASIK. Monofocal IOL give a good distant vision (OV). But the patient, d ue to the natural multifocality of the cornea, can ha ve also an intermediate vision (iv): that's called the depth of focus. By a modifica tion of the SA of the cornea it w ill be possible to increase the dep th of focus until patient will be able to read without glasses. RELATIONSHIP BETWEEN Q VALUE ASPHERICITY AND AMOUNT OF SPHERICAL ABERRATIONS

The d ifficulty is to understand that, the Q value asphericity and the spherical aberrations (SA) make change together, but they haven't got the same 0 reference. Q value is due to the d ifference of kera tometry between the center cornea and the medium cornea (6.5 mm OZ). Ifkeratometry increase from the central to the peripheral cornea Q value is positive, and the cornea profile is ca lled oblate. At the contrary Q value is negative an d the cornea profile is called hyper-prolate. In normal cornea mean Q < 0 (- 0.25) and SA > 0 (0.25)1). If the keratometry is constant the cornea profile is spherical Q = 0, and SA » 0 (1)1 or more). If Q value = - 0.55 then SA = O. These basements are checked up just below. Q value is measured by the topograph, for instance the TOPOLYZER of Wavelight, it can give also the amount of SA due to the cornea. At the contrary the aberrometer like ANALYZER of wavelight, measure the total SA of the both 458 corneal and crystalline lens. Generally negati ve SA occurred in the crystalline,

Mon%cal HOA Free IOL to Correct SccondanJ Presby-LASlK

SA> 0

I»

Fig. 4: Q value and SA relationship

I SA is proportional to accommodation "f'l'

Cheol/It IIQ II JK II I'Opul,>,,,,,, ~h"ly nn ~1>~n'lM I" W 'v" 'h." ,'hon~ .. 95% of eyes are wi thin 1 0 of emmetropia. Efficacy excellent: uev A as well as BSeVA are Significantly better than preoperative. 1rnprovement in BSeVA is very common and also occurs in eyes that were previously regarded as amblyopic. This happens more often in the myopia group and the improvement in best corrected vision is probably caused by the magnification effect of the PIOL. Safety. In most reports no eyes lost any line of BSeV A. Serious complications are rare . Please refer to complications. Qualities of the Artisan Toric PIOl

488

This is also a PMMA PIOL. The optic diameter is 5.0 mm.

Artisan, ToricA rtisan and Artiflex Phakic Intraocular Lenses

1-

"~

Study results

1o0 Preop BSCVA J

Efficacy

Postop UCVA

100%

"-

90%

-

80% 70%

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w

60%

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Efficacy index (UCVA postop/BSCVA preop) 1 "01 at 1 year postop

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Fig . 13: Efficacy index at 1 year postoperative

PIOl Predictability

e:

0

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Fig . 14 : PIOl predictability index

489

Instant Clinical Diagnosis in Ophthalmologt) (Refractive Surgen)

The length of the IOL including the haptics is 8.5 nun. The thickness of the lens varies between 0.96 and l.2 nun depending on the dioptric power of the lens. It is available in 0.5 dioptre spheric increments from -2.5 to -21.0 d ioptres as well as from +2.00 to + 7.50 combined with the required cylinder. The cylinder is available from -2.0 Oioptre to -7.50 at whatever axis necessary. The toric Artisan is custom made and delivery is 8-10 weeks after order approval. A unique feature of this PIOL is the variation of the cylinder position relative to the shape of the PIOL. The cylinder can be ordered in such a way that the surgeon can onl y implant the PIOL in a horizontal position to ensure the correct cylinder axis. But this may vary and the surgeon should be aware of the possible va riation in cylinder position. The lens is also fixated to the iris in two spots using an iris enclavating technique. Indications for the Artisan Toric PIOL

1. Myopic or h yperopic astigmatism with sphere of -20.0 to -2.0 as well as +2.00 to +6.00 combined with: 2. Astigmatism of -2.0 to -7.50 diopters 3. Phakic eyes 4. ACO more than 3.2 nun. 5. Normal corneal endothelium. 6. Normal iris. 7. Stable keratoconus with good BSCVA 8. Correction after Lasik overcorrection 9. Correction after PKP.

Contra indications for Toric Artisan [same as for Artisan PIOL] 1. ACO less than 3.2 nun. 2. Bulging iris. 3. Small ACO, i.e. deep enough but because of short white to white and high K-readings the peripheral haptic of the PIOL w ill be too close to the endothelium. 4. Cataract.

5. Recurrent or chronic uveitis.

490

6. 7. 8. 9.

Angle closure glaucoma. Wide angle glaucoma. Small refractive errors. In this case Lasik may be better. Astigmatism of less than -l.7S 0 [Here we use Artiflex PIOL]

Artisan, Torie Artisan and Artiflex P//akie IntraoClllar Lenses

~

Study results Safety

60%

N=305

,40%

-

'">-

" w

20%

0%

n

n Lost 1

Unchanged

Gained 1

Gained 2

Gained 3

Change in BSCVA

IL

Safety index (Postap BSCVAlPreop BSCVA) 1.10at1 yearpostop

Fig. 15: Safety index at 1 year postoperative

Study results Stability 4

e: LU

0

N = 30 5 -0,12

(f)

c --4 .2 1) ro

'""

'"

-8

-7,23

-12~--~-~~-~--~--_--~

Preop

1 day

1 week

3 months 6 months

Average SE at 1 day postop

1 year

= -0.04 D ± 0.4

SE remains stable until 1 year postop

Fig. 16: Stability index

491

Instmrt Clinical Diagnosis in OphthalmologtJ (Refractive Surgery)

10. Patient yo unger than 18. 11. Spherical or astigmatic error outside the available diopters of the Artisan PIOl's. 12. Endothelial cell count < 2000 per square rnrn. 13. Corneal endothelial dystrophy. 14. Insufficient iris to support PIOL. Surgery for Torie Artisan PlOL The surgery is essentially the same as for Spheric Artisan PIOl A few important adjustments must be made for the fac t tha t this is a toric PIOl Preoperative marking of the enclavation sites. The surgeon must be aware of the axis of the cylinder relative to the shape of the PIOL. This means that every PIOl may potentially be implanted in a different axis. A simple way of marking the enclavation sites of the PIOl is to make small YAG laser burns on the iris at the correct spots preoperative. An alternative for marking the correct cylinder axis is to use a surgical marker to mark the limbus. Anesthesia. As for spheric Artisan this surgery can be performed under topical, peribulbar or general anesthesia. Incision.

A superior 5.5 rnrn scleral tunnel under a limbal based conj unctival flap. The incision wid th is 0.5 mm larger than the diameter of the lens optic. Two limbal clear corneal parasyntheses are made at the correct positions, keeping in mind the marked enclavation sites and the surgeon's technique. After making the incisions, acethylcholine is injected into the anterior chamber to create instant miosis.

This is followed by an OVD into the anterior chamber to fill the AC. It should be a cohesive OVD to prevent adhesion to the intraocular structures. This OVD should be easily removable after the PIOl has been inserted. Then the PIOl is introduced into the AC. In the anterior chamber it should be rotated to the correct position and must be well centered over the pupil. At this stage the Toric Artisan is held with a special holding forceps and the first pair of haptic claws are attached to the iris at exactly the correct spot as marked preoperative with the YAG laser. This procedure is repeated for the second pair of haptiC claws, once again making sure that it is enclavated at exactly the correct position . Now the peripheral iridotomy can be done superiorly but not always precisely 492 at 12 o'clock.

Artisall, ToricArtisan and Artiflex Pllakic Intraocular Lenses

ARTISAN® Lens Manufacturing Information PMMA lenses are manufactured by using Compression molding technology. During the compression molding process the molecular structure of PMMA (fig . 1) is enhanced by redistributing the molecules into longer chains (fig .2). This results in a much stronger material. Compression molding technology gives a high tensile strength, combined with superb flexibility of the lens haptics. The risk of fracture is minimal. The tumbling process gives a special surface treatment to the PMMA lenses. Ultra smoothness of the haptics is the result.

Figs 17 A and B: Artisan PIOl specifications

0000 Model 206W ARTISAN ""

ARTISAN '"" hyperopia,

myopia lens

model 203W

ARTISAN "" myopia, model204W

ARTISAN"" aph akia model 205Y

1991

1992

1997

1998

Fig. 18: History of artisan lens

493

Instant Clinical Diagnosis in Oplt tltalmologz) (Refractive Surgen) Then the OVO is removed completely. The incision as well as conjunctiva is closed. Follow-up Visits are schedu led for 1day, 1 week, one month, 3, 6, 12 months. Complications Preoperative complications • Anaesth etic complica tions Some patients, particula rly young people, cannot tolerate topical anesthesia and must receive peribulbar or general anesthesia. Young patients may preler general anesthesia to peribulbar injections. Calculating the Power of the Toric PIOL

TIUs is done by the manufacturer Ophthec. It is based on relractive information provided by th e surgeon. Intraoperative complications: Wound complications. Some scleral tunnels may leak without the use 01 sutures. OVO complications. During enclavation the OVD may escape from the AC and should be kept at adequate volume to facili tate surgery. Inadequate volume of OVD in the AC will not protect the endothelium and may lead to en dothelial damage. Insufficient OVO is necessary to elevate the PIOL to make it possible for the surgeon to grasp it. Insufficient removal of the OVO may cause postoperative wide angle secondary glaucoma. Complications of Position of the Toric Artisan PIOL

• Any decentration should be avoided and more so because this is a toric lens • Misalignment of the cylinder axis: If the PIOL is not positioned in the correct axis, a postoperative refractive error will be the result. • Sometimes the first attempt to enclave the PIOL results in a wrong position 01 the PIOL. If this happens it should be rectified immediately. It is very easy to disenclavate the lens by just pushing the iris bach through the claws of the lens. Complications of the peripheral iridotomy /iridectomy • A peripheral iridotomy is better than an iridectom y. • However it may h appen that th e iridotomy is not pa tent and this may 494 lead to postoperative acute pupil block glaucoma.

A rtisan, Torie A rtisan and Artiflex Plrakie In traoelliar Lenses

History

-===--

~

~

ARTISAN"" lone lens 90°

ARTISAN"" phalic tOL

1999

1999

2005

ARTISAN""

tone lens O'

Fig. 19: History of artisan lens (contd)

Comparison chart Power range (S)

ARTISAN®

ARTIFLEX®

+ 12.00 up to - 23.5 0

- 2.0 0 upto-14 .S 0

Power range (5)

2.0Dupto7.5D

None

Body 0 Overall 0

5.0 mm IB.O mm

6.0mm

Optic material Refractive index Optic design Optic configu ration Anti glare edge design

Haptic shape Cross flow design Recommended incision width

Passport system

7.5 mm 18.5 mm

8.Smm

PMMA

Hydrophobic polysiloxane

1.49

1.43

Spherical

Polynomial

Convex-concave

Convex-concave

no

Yes

Claw®

Claw«l

4 Lateral side ports

4 Lateral side ports

5 .2 mm 16.2 mm

3.2mm

None

Insertion spatula flo!

Instruments

ARTISAN" kit

ARTIFLEX® kit

Viscoelastics

ArtiVisc N I ArtiVisc plus TM

ArtiVisc TN I ArtiVisc plus TM

Fig. 20: Comparison chart of specifications of PIOLs

495

Instant Clinical Diaguosis in OphthalmologtJ (Refra ctive Surgery)

• A peripheral iridectomy may be too large and give rise to various postoperative symptoms like awareness of the PI, glare, etc. PPP PI. Postoperative Complications

[These are very similar to those of the Artisan spheric PIaL] • Postoperative mild uveitis will ocasionally be present. • In case of a non-patent periphe ral iridotomy ac ute pupillary block glaucoma may develop within hours after the surgery. • Corneal ed ema should not occur but in case of excessive manipulation it is possible. If the crys talline lens is to uched during surgery it may cause early postoperative traumatic cataract.

• Hemorrhage [hyphema] is very ra re. • Infection, e.g. endophthalmitis is also rare. • Decentration of the PIaL will im pact negatively on visual acuity and w ill also lea d to va rious optical disturbances such as halo, glare, monocular diplopia, etc. • A frequently encountered com plication is the presence of unwanted postoperative astigmatism. This is usua lly the result of too tight sutures in the superior scleral tunnel which creates with-the-rule astigmatism. As time goes by this astigmatism reduces to acceptable levels but most patients find it very disturbing. That is one of the very good reasons why the Artiflex foldable PIa L was developed. Results of the Toric Artisan PlOl

Predictability excellent: If the preoperative refractive measurements are correct, the predictability is excellent and >90% of eyes are within 1 0 of emmetropia. Efficacy is excellent: UCV A as well as BSCV A are significantly better than preoperative. As with the other PIaL's some patients gain as many as 3 or more lines of best corrected vision. Safety: In most reports no eyes lost any line of BSCVA. Complications can happen as d iscussed. However, the complication rate is low and very few serious complications ocelli. ARTlFlEX FOLDABLE IRIS CLIP PIOl

Qualities of the Artiflex Spheric PIaL. • It is also an Iris fixated PIaL • It has a foldable optic made of polysiloxane

496

Artisan, Toric Artisan and Artiflex Phakic Intraocnlar Lenses

• The optic d iameter is 6 mm • The length of the IOL including the hap tics is 8.5 mm • The Artiflex PIOL has PMMA haptic claws into which iris must be endavated in a similar fashion as with the Artisan PIOL • A specia l spatula is provided with the Artiflex PIOL to fold the PIOL before introducing it into the AC. • The Artiflex IOL is only a Myopic Spheric PIOL and is available in 1 diopter increments from -14.5 to - 2.00 diopters. Indications for Use of the Artiflex PIOL

These indications are basically the same as for the Artisan spheric PIOL. The Artiflex PIOL will probably soon replace the Artisan PIOL for myopia. Indications 1. Refractive errors between - 2 to - 15.0 [Lens is - 2.0 to - 14.5] 2. Phakic eyes 3. Anterior chamber depth more than 3.2 mm. 4. Normal corneal endothelium and clarity.ECC >2000. 5. Cornea l astigmatism of -1.750 orIess. 6. Normal pupil and flat iris. Contra-indications

1. ACO less than 3.2 mm 2. Bulging iris 3. Small ACO, i.e. deep enough but white to white too short to provide ample space in the AC 4. Cataract 5. Recurrent or chronic uveitis 6. Angle closure glaucoma 7. Small refractive errors. In this case Lasik may be better 8. Astigmatism of more than - 1.75 D [Here we use toric Artisan PIOL] 9. Insufficient iris to support PIOL 10. Endothelial cell count < 2000 cells/ mm 3 Surgery

See Figure 10. Anesthesia

The main advan tage of the Artiflex IOLis that it can be inserted through a clear 497 corneal incision.

Instant Clinical Diagnosis in OphthalmologtJ (Refractive Surgery)

Therefore the operation can quite comfortably be done under topical anesthetic combined with intracameral lignocaine. 1his surgery can also be performed under peri bulbar or general an esthesia. As w ith the Artisan lens it is the surgeon's choice but will naturally be influenced by patient expectations and preferences. In the USA and Europe topical anesthesia is popular. Incision

More than one ulcision type is possible. An excellent option is a superio r clea r corneal incision. It can be made with

a diamond knife and the ainl is to make the incision 3.2 mm wide and 1.5 to 2 mm in length. This is followed by two limbal clear corneal parasyntheses at the 3 and 6 o'clock positions. These are used to introduce the enclava tion fo rceps to enclavate the iris.

Some surgeons prefer to make ve rticallinlbal pa rasyn theses at the 2 and 10'0 clock positions. Through these they introduce a special enclavation needle to do the enclava tion. After making the incisions acethylcholine [miochol or equivalent] is injected in to the anterio r chamber to create ins tant miosis.

1his is followed by an OVD into the anterior chamber to fill the AC It should be a cohesive OVD to prevent adhesion to the intraocular structures. It is mand atory that this OVD should be easily removable after the Artiflex lens has been inserted. Then the Artiflex PIOL is removed from its container and loaded onto the insertion spatula. This little procedure is very easy but needs to be executed correctly. The Artiflex PIOL is gently introduced into the AC with the help of the injector. When the optic of the Artiflex PIOL is well into the AC the injector can be retracted. 1his maneuvre will leave the Artiflex lens in the AC In some cases the follow ing haptics could still be outside the eye and can gently be moved forward into the AC It may well be asked: why would the following haptics not enter the AC with the PIOL? The problem is that the injector's tip may reach the inferior AC angle before the haptics are altogether in the AC superiorly. It is then safer to retract the injector ra ther than d amage the inferior AC angle. If the following haptics are still outside the AC it ca n be moved inwards without a problem. Once in the anterior chamber the Artiflex PIOL should be rotated to a horizontal position. Care should be taken to make sure it is well cen tered over 498 the pupil.

Artisan, ToricArtisan and Artiflex Plrakic Intraocular Lenses At this stage the PIOL is held with a special holding forceps. These holding forceps are different from those used for the Artisan PIOL. It is important to note that only the hap tics are held and the optic should never be touched with these forceps. As with the Artisan PIOL the first pair of haptic daws are attached to the iris by endavating iris between the two curved haptic daw tips. The enelavation can be done using special forceps or a special enelavation needle. This procedure is repeated for the second pair of haptic daws. Now the PIOL is securely attached to the iris and the peripheral iridotomy can be made at the 12 0' d ock position. Then the OVO is removed very thoroughly and the AC is filled with BSS. If required the incision edges may be hydrated. No suturing is necessary. Follow-up 1day, 1 week, 1 month, 3, 6, 12 months. Results

Fast visual recovery: Because the elear corneal incision ind uces very little astigmatism the visual recovery is very quick. Many patients w il have 1.0 unaided vision the day after surgery. Efficacy: Excellent visual acuity results. The efficacy index [UCV A postoperative/BCV A preoperative] was measured as 1.01 in one series. Due to the high quality of the Artiflex lens and the stability and predictability of the lens the visual acuity is excellent. Final UCV A after 3 months is often 20 /20 or better and BSCVA is often better than preoperative. As with other lenses of the Artisan group a high percentage of patients will experience up to 3 or more lines of improvement of BSCV A, probably due to magnification of retinal images. High predictability: The preoperative calculations are extremely accurate and it provides exceptionally good predictability. Safety: The surgery is fast, smooth and atraumatic. Very few significan t complications are reported. The safety index was 1.10 at 1 year postoperative. Stable results: The endavation technique is remarkably stab le and the lens position will not change during any no rmal physical activity [boxing is not advocated!] Therefore the result is maintained over many years. Complications

Preoperative • Anesthetic complications Some patients cannot tolerate topical anesthesia and mu st receive 499 peribulbar or general anesthesia

Instant Clinical Diagllosis in Ophthalmology (Refractive SlIrgery)

• For yo ung patients the peribulbar injections may also be a problem and they rna y be very comfortable with general anesthetic • Calculating the power of the PIOL. This is done by the manufacturer Oph thec. 1t is based on refractive information provided by the surgeon. INTRAOPERATIVE COMPLICATIONS Demanding Surgery

The surgery is actually quite easy, except for one maneuvre. The enclavation of the ha p tics can be very diffic ult, and fo r this proced ure good training is recommended. Wound Complications

The incision is remarkably free of complica tions but wo und leakage is an unlikely pOSSibility. A clear corneal incision of 3.2 mm should give rise to not more than approxinlately -0.25 to -0.50 diop ters of astigmatism. OVD Complications

During enclava lion the OVD may escape from the AC and should be kep t at adequate volume. Insufficient volume of OVD will lead to endothelial touch and damage. It will also make it very difficult to pick the PIOL u p with the hold ing forceps when mani pulating the lens. A cohesive OVD should be used to lacilitate removal 01 the OVD from the AC.

Remova l 01 the OVD at completion of the operation is very im portant to avoid postoperative acute secondary wide angle glaucoma. Complications of Position of the PIOl

It is extremely important to place the PIOL over the center of the pupil. Any

decentration should be avoided but if it d oes happen it is better to err towards the nasal side because most eyes have a slight nasal displacement of the visual axis. Sometimes the first attempt to enclava te the PIOL results in a wrong position of the PIOL. If this ha ppens it should be rectified in1mediately. It is very easy to disenclavate the PIOL by just pushing the iris bach through the claws of the PIOL.

500

Artisa", ToricArtisan andArtiflex Phakic [n traocular Lellses

Complications of the peripheral iridotomy/iridectomy A periphera l iridotomy is preferred to an iridectomy. However it may happen that the iridotomy is not patent and this may lead to postoperative acute pupillary block glaucoma. A peripheral iridectomy may be too large and give rise to various postoperative symptoms like awareness of the PI, glare, etc. Postoperative Complications

Postoperative mi!d uveitis will ocasionally be present. In case of a non-patent peripheral iridotomy acute pup illary block glaucoma may develop within hours after the surgery. Corneal edema might occur after excessive manipulation during surgery. Lens touch d uring surgery may cause a traumatic cataract. Hyphema is very rare. Infection, e.g. endophthalmitis is also rare. Decentration of the PIOL may cause reduction of visual acuity as well as various optical disturbances such as halo, glare, monocular diplopia, etc. Late Complications

At 1 year the following complications were reported Pigment deposits: 5.6% Haloes: 5.2% Glare: 3.6% Non pigment deposits: 3.6% Synechiae 0.3% Explantation 0.3% Lens exchange 0.3%. EFFECTS OF ARTISAN AND ART1FlEX PHAK1C IOl'S ON THE EYE Effects on the Endothelium

A main concern for any IOL in the anterior chamber would always be its effect on the end othelium. A number of good studies have been done to evaluate this. The concensus of opinion is that the initial surgery w i! cause a loss of endothelial cells of 0 to 4%. After this initial loss of endothelial cells the endothelial cell count will not show any Significant deterioration for as long as 10 yea rs postoperative. A recent multicenter stud y done on the Artiflex PIOL has shown 0% endothelial cell loss after the first yea r postoperative. 501

Instant Clinical Diagnosis in Ophthalmologt) (Refractive Surgen)

The present belief is that the PIOL may not anywhere be closer to the endothelium than l.0 mm. That is why an AC depth of 3.2 mm preoperative is so important. If the AC is shallower, the peripheral edges of the PIOL will be too close to the endothelium. Effects on the Iris

The claw-haptic of the PIOL does cause some iris depigmentation at the site of enclavation, but if enough iris is enclava ted, this will not lead to any problems. Iris necrosis and PIOL dislocation is extremely unlikely. If the initial enclavation is not well done and only a very thin piece of iris is enclavated, it ma y well lead to erosion of the iris by the claw-haptics, which in turn will cause disinsersion of one or both haptics and therefore dislocation of the PIOL into the AC. The peripheral iridotomy or iridectomy will cause some pigment dispersion into the AC and this pigment will be most visible on the PIOL as well as the crystalline lens and the endothelium. No reports of secondary pigmentary glaucoma due to the small amow1t of pigment dispersion have corne to our attention. Effects on the Crystalline Lens

The main concern for the patient's crys talline lens is of course the formation of cataract.

The most dangerous time is during surgery. If the crystalline lens is inadvertently touched it may lead to instantaneous traumatic segmentary cataract.

In case of good successful surgery the chances of development of cataract at a later stage is not more than that of the normal population. The fact that the PIOL is in the AC, has very little effect on the crystalline lens. Effects on the Intraocular Pressure

The main concern is postoperative pupillary block glaucoma in the presence of a non-patent peripheral iridotomy. Obviously prevention is better than cure. Make sure the PI is open during surgery! The Artisan and Artiflex PIOL's have no proven long-term direct effects on the lOP. These PIOL's should not be used in the presence of angle closure glaucoma. Effects on the Anterior Chamber Angle

These PIOL's do not touch the anterior chamber angle and will have no effect 502 on the angle.

Artisall, Toric Artisall mid Artiflex Phakic Illtraocular Lellses

A review of the benefits of the Artisan or Artiflex PIaL's compared to other PIaL's: • It has the longest clinical history of all the PIaL's. The first Artisan PIaL was implanted on November 2, 1986. • One size fits all: Other PIaL's need sizing for a proper fit. This applies to the anterior chamber as well as posterior chamber PIaL's. • Extremely versatile: The Artisan lenses are designed for aphakia, myopia, hyperopia as well as astigmatism. • Reversibility of fixa tion: Easy to reposition or exchange. • Safe distance from crystalline lens: Virtually no PIaL related lenticular opacifjcations occur. • Safe distance from endothelial cells: The initial cell loss is surgery related. • High predictability: 98% of patients obtain a refractive resu lt within 1 Diopter of emmetropia. • Excellent Centration: Once fixated the lens will not decenter. • Normal pupil. The lens does not affect dilatation or constriction of the pupil. SUMMARY

The Artisan group of iris fixated PIaL's is an excellent option when considering refractive surgery. It is very effective, safe, predictable and stable and can be often used when other modalities ma y be inadequate.

503

Orthokeratology

Fig. l A: Pre lit

Fig. 2A: 15t generation flat conventional lens

Fig. 18: Post ortho-K

Fig. 1C: 2 weeks after suspend ing

Fig. 28: 2nd generation

Fi g . 2C: 3rd generat ion

three -zone reversegeometry

four-zone reverse-geometry

Fig. 3: Typical fluore-scein pattern (ESA-ortho6)

505

Instant Clinical Diagnosis in OplJtllalmologtj (Refractive Surgenj) cases, the final result can be achieved with only one pair of lenses, in a period of time between one and two weeks. Treatment of astigmatism is controversial. Work is in progress to design toric reverse-geometry lenses for the specific treatment of astigmatism, and results are awaited with interest. Treatment of hypero pia and possibly presbyopia through corneal steepening is also under current investigation; preliminary studies suggest that corneal steepening with apical clearance lens designs may be possible, although the time scale and limits to this procedure require furthe r study. OVERNIGHT ORTHOKERATOLOGY

In the last years, orthokeratology procedures involve the overnight use of contact lenses: the cornea is reshaped during the sleeping time and lenses are taken off when the patient wakes-up. In most cases, the effect lasts until the evening. This proced ure has the advantage of eliminating some environmental factors (dust, wind, conditioned air, sports) that can give trouble during the day; in addition, the pressure of closed lids improves the rapidity of corneal molding. For overnight wear, high oxygen permeable materials are necessary to provide sufficient oxygenation to the cornea, even if lids are closed. When rigid gas permeable (RGP) lenses are worn during waking hours, oxygen can reach the cornea via two mechanisms: by circulation of oxygen-rich tears behind the lens, d ri ven by a lid-activated tear pump, and by diffusion through the lens material. An estimated 10-20% tear exchange occurs with each blink under a rigid lens. PoIse estimates a tear exchange per blink of only 1% under soft lenses, due to their greater diameter and flexibility. On the contrary, both lens types provide oxygen to the cornea during closed-eye wear by diffusion through the lens material. Thus, soft and RGP lenses of comparable Dk/ t will induce similar levels of overnight edema. On awaking, the lid-activated tear pump is much more efficient with RGP compared to soft lenses, so oxygen is supplied in more quantity, facilitating rapid corneal recovery from overnight hypoxic stress. And rasko and Holden, et alhave demonstra ted that the cornea deswells more rapid ly after overnight wear ofRGP lenses than with soft lenses, because of the greater tear pumping efficiency of rigid lenses. This recovery is even more rapid if we talk about overnight wear, with the lens taken off on wakening, rather than continuous wear. The removal of the lens allows both cleansing of the lens and the elimination of debris and waste products trapped behind the lens.

506

Orthokeratologtj

Fig . 4 : Decentration of the molded area due to

dislocation of the lens

Fig. 5 : Corneal war page due to lens binding

Fi g . 6 : Pre : RX 51. - 2.25 ; Posl: UC VA 12/10

507

Instant Clinical Diagnosis in Ophthalll101ogtJ (Refractive SIII'gery) REVERSE GEOMETRY CONTACT LENS DESIGN

Modern contact lenses for orthokeratology have a curvature profile that is "reversed" from traditional rigid lens design, so they are usually defined "reverse-geometry contact lenses". Traditional lens designs have secondary and peripheral curves flatter than the central curve of the lens. On the contrary, reverse-geometry lenses have one or more peripheral curves steeper than the curve of the optical zone. In modem reverse-geometry lenses for orthokeratology, we can identify four main functional zones: Optical Zone, Reverse Zone, Alignment Zone and Peripheral Zone. Usually reverse-geometry lenses for orthokeratology have a diameter larger than traditional RGP lenses. The back optical zone determines the shape that the cornea will assume after the corneal molding, and so it determines the amount of refractive error corrected by the orthokeratological treatment. Usually, it is a spherical curve. The radi us of curvature of this zone is calculated in order to get the desired orthokeratological effect. The lift of peripheral curves over the cornea around the Optical Zone creates a tear reservoir.

The Reverse Zone allows the joining of the Optical Zone with the Alignment Zone. In the reverse zone, there are one or more curves s teeper than the back optical zone. The Alignment Zone is the bearing zone of the lens; it gives stability to the lens and keeps it centered on the cornea. In some particular lens design, it also enhances the corneal molding, putting a pressure in the periphery of the cornea that aids the redistribution of corneal tissue towards the optica l zone. The curvature of the alignment zone is flatter than the reverse zone, but steeper than the optica 1zone. The Peripheral Zone allows the lens ed ge to lift from the cornea, to achieve an adequate tear turnover under the lens. This tear exchange is necessary for two reasons: to get in new tear liquid to oxygenate the cornea, an d to get out the debris and metabolic residuals formed under the lens. If the lens has a proper aligmnent and a right lift in the Peripheral Disengagement Zone, during the blinking we have an effective pumping action of tear fluid. Besides this primary function, the tea r meniscus under the peripheral curves allows a capillary attraction helping the lens to keep centered. The edge lift has other functions too: it controls the pressure of the edge of the lens minim izing the risks of corneal insult and helps the removal of the lens by mean of lid tension . The curvature of the Peripheral zone is fl atter than the Alignment zone. 508

OrtllOkerat%:5'J

Fig. 7: Pre: AX Sph. - 6.00; Post: Sph. - 0.75

Fig. 8: Pre: AX -7.50 -0.50 x 180 ; Post: UCVA 9/10

509

Instant Clinical Diagnosis in Ophthall1lol0I5'J (Refractive SltrgenJ) THE IDEAL FITTING

Reverse-geometry contact lenses are designed in order to produce a hydrodynamic force on the cornea, that aims at causing epithelial ceLis to migrate, so as to obtain a change in the first ceLlular layers. In order for this force to work efficaciously, the fitting should have definite characteristics as regards the position of the lens, its movement and the clearance between the cornea and the lens. Let us analyse them in detail: • Positioning: The centration of the lens is critical for the efficacy of orthokeratological effect. Decentred lenses cannot produce the desired myopia reduction; it may cause an increase in astigmatism and corneal

distortion. A poorly centred lens can induce poor visual acui ty after lens removal.

• Movement: The lens should have a 0.2-1.0 mm blink induced movement. Orthokeratology contact lenses should show less mo vement than conventional lenses. • Fluorescein pattern: The typica l fluorescein pattern of reverse-geometry lens fitting should show an image characterised by concentric rings: dark center (minimal apical clearance, without touch), green ring (tear reservoir, with variable thickness, depending on the corrective effect, usually between 30 and 50 microns), dark ring (mid-periphery touch, alignment zone), thin green ring (edge lift, 80-100 micron). The transition between the different zones should be blended. After first adapta tion, there should not be air bubbles. This would indicate an excessive lift in the tear reservoir zone.

SELECTION OF PATIENTS

Usually orthokeratology can be used in low and moderate myopia, up to 6.00 0 , even if associated with low astigmatism. In higher myopias, orthokeratology can reduce the refractive error, w ithout correcting it totally. This kind of correction can be useful as well, in people who wish either less dependence on optical aids, or who wish to wear more functional and well-designed spectacles. In most cases, this technique is contra-indicated in high astigmatism. Primarily, o rthokeratology is indicated when m yo pic patients are contraindicated to refractive surgery or they are unwilling to undergo any surgery. Not aLi myopic patients are willing to undergo an operation, however safe it is, and however low the risks of failure or complications may be. Besides not all myopic are suitable for surgery, for example due to their age or because they have a myopic progression: refractive surgery is not ad visable 510 until myopia is not stable definitely. Refractive surgery should not be performed

Orthokeratology .50,-_ _~R~'~frn~dj~·~"~O~"~too=m~'_ _- ,

Quality of vision scores

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_ Morning Afternoon

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o

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Fig. 9: Refractive outcome, quality of vision score , efficacy index, and safety index

Fig. 10A: Pretreatment corneal wave-front

511

Instant Clinical Diagnosis in Opiltilalmoiogtj (Refractive SlI rgenj) on young people or teen-agers. Also in cases of young adults we have to be sure that there are not fWlctional conditions promoting a future myopic progression. As w ell, some patients have a low refractive error and wish nlore independence from standard corrective aids, spectacles or contact lenses. Pilots,

athietes, police officers, fire fighters, etc. might need more independence from corrective aids, without undergoing surgery. LIMITS

Orthokeratology is not suitable to every patient, because it ha s some contra indications and Limits. Orthokeratology is contraindicated in all those ocular cond itions that do not allow the use of conventiona l contact lenses. These are: acute and subacute inflammations or infection of the anterior segment of the eye; any eye disease, injury, or abnormality that affects the cornea, conjunctiva or eyelids, which ma y be exacerbated by wearing contact lenses; any systemic disease, which may affect contact lens wear, as inunune system diseases, or metabolic dysfunctions; allergic reactions 01 ocular surfaces or adnexa which ma y be induced or exaggerated by wearing contact lenses or by the use of contact lens solutions; alterations of tears (d ry eyes). Lintits of orthokeratology treatment ha ve to be explained in detail to each candidate. At the beginning, it is necessa ry to adapt to rigid contact lenses, which in a few cases can be troublesome in the initial period, even if this trouble is reduced to the minimum in overnight wear. Then, results depend on pre-treatment ocular conditions: corneal shape, lid position and action, corneal tissue response, presence or absence of astigmatism, etc. and usually 20/ 20 can be achieved only for low or middle myopia. For some patients, the main limitation of orthokeratology is that results are temporary. Actually, changes achieved with orthokeratology do not last forever. To maintain the reduction of myopia, lens wear have to be continued on a prescribed wearing sched ule. At the begiruting of treatment, the clear vision period ma y last few hours, and then visua l ac uity begins to decrease progressively. With time, we have an increase of the clear vision period after lens removal. When vision is no longer acceptable, the patient needs to wear retainer lenses. For people who wish to get rid of any correction for good, the temporary results are definitely a limitation. However, in some cases, reversibility of treatnlent can be an advantage. 512

Orthokeratologtj

Fig . lOB : Postortho-k corneal wave-front

Fig . 11: Confocal microscopy

580 570 560 u 550 :.5 540 •c 530 u ~ 520 c 510 • () 500

[ ~ •c ~

BMorning OEvening

"

"

Fig. 12: Changes in

BL

1D

1W

2W

1M

3M

cen tral corneal thickness over time

513

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) RISK ANALYSIS

Even if the recent literature reports a series of cases of microbial keratitis, we do not expect that contact lenses fo r orthokeratology may provide a risk that is greater than other contact lenses. The incidence and prevalence of microbial keratitis related to corneal reshaping contact lens wear is not known. Any overnight wear of contact lenses increases the risk of infection, but it is not known whether the risks of microbial keratitis are greater fo r corneal reshaping overnight contact lens wearers than other form of overnight contact lens wear. However, besides the side effects that are common to all rigid contact lenses, there are some specific complications due to corneal distortion. Sometimes we observe some corneal irregularities that can be due to lens displacement. Usually they are slight and do not affect quality of vision. Sometimes we have a greater decentration of the molded area. This decentration may be due to dislocation or binding of the lens. In this case, strong irregularity of corneal profile may cause an inadequate refractive condition and high order aberration, troubling effects in twilight and night vision. Since orthokeratology does not produce permanent and irreversible corneal changes, when such a problem occurs, we can modify lens p arameters until we obta in a satisfactory result in terms of both positioning and correction. In most problematic cases, we have to stop lens wear. As rega rds corneal staining, w e can have this problem because of both a loose lens, w hich causes mechanical abrasion on corneal epithelium, and a tight lens, which adheres to the cornea. Moreover staining may be due to debris trapped behind the lens or to deposits on the lens. Finally, it is reconunended that ongoing education be provided to practitioners and staff regarding saiety, informed consent, and prevention of potential problems, with special emphasis on the critical need to properly and thoroughly disinfect lenses that will be worn overnight. SOME CASES

The following figures show some successful cases. Efficacy and Safety of Overnight Orthokeratology by Means of a Customized Hexa-curve Reverse Geometry Lens

A growing numbe r of clinical studies ha ve reported on the efficacy of modem orthokeratology using a range of different reverse-geometry lens d eSigns. One of u s (AC) patented a new design a nd calculation method to customize a multi-curve reverse geometry lens. A prospective, randomi zed study to 514

OrtilO k erat%gtj

evaluate the safety, efficacy, predictability, stability, quality of vision and adverse reactions of overnigh t orthokeratology by means of this customized hexa-curve reverse geometry lenses (ESA ortho-6) in hyper-Ok gas-permeable material (Boston XO, hexafocon-A) . Fifty eyes of 25 myopic patients aged from 11 to 44 years, without any tear, corneal, ocular and / or systemic disease at the baseline time and without any previous ocular surgery were treated. The baseline refractive error was from1.00 to -6.00 0 spherical equivalen t, WTR astigmatism up to 1.50 0 and ATR astigmatism up to 1.00 O. The results sh owed that the cornea responds rapidly wi th significan t (p < 0.05) central corneal flattening and improve ment in visual acuity after just 60 min of lens wear. The corneal shape changes from prolate to oblate asphericity after 1 night of wear; in the majority of cases im provement in unaided visual acuity up to 0.1 Log MAR can be obtained fo r a t least 12 h after lens removal in the first week of treatment. These changes were sustained at 1 and 3 months. In the first week, there was a significant improvemen t in subjective ra tings of quality of d ay and night vision (p < 0.05) but a Significant increase of corneal spherical aberration (p < 0.05) due to post-treabnent oblate sh ape of the cornea. The spherical aberration was correlated with the amount of trea ted myopia and with p upil diameter, while coma-like aberration was correlated with the displacement of the pupil as regard s the geometric center of the cornea. Subjective ratings continued to improve after objective measures stabilized at 1 week. Biomicroscopy showed no corneal infiltrates or ulcers; there were son1e observations of grade 1 fluorescein staining of the cornea, and imp rinting in the morning that disappeared in the evening; no other significant ocular adverse events were observed during th e trial. No Significant change was observed in the central thickness of the cornea (p > 0.28). No significant ch ange was found in the intraocular pressure (p > 0.08). Specular microscope showed n o measurable chan ges in the endothelium . Confocal microscopy: in several subjects, b asal layer of the epithelium showed larger an d less regular cells after the trea tm ent. We can explain this phenomenon with a mild cellular edema d ue to the hypoxia or the mech an ical effect of the treatment. A few subjects showed a slight increasing in reflectivity of Bowman's layer and of anterior s troma. The appearance and the activation rate of keratocytes were not modified. Therefore, the slight increase in reflectivity could be explained by a mild increasing of corneal glycosa minoglycans prod uction, that is a

reversible phenomenon due to an aspecific reaction of anterior stroma to different traumas. No other significant alterations were observed in the anterior epithelium, sub basal nerve plexus, mid an d deep stroma and end othelium.The 515

Instant Clillica l Diagnosis in Ophthalmologtj (Refractive Surgery) results of this study suggest that the corneal epithelium can be molded or redistribu ted very rapidly in response to the tear film forces generated behind this reverse-geometry lens design. Safety and efficacy of the procedure appear to be fa vorab le without significant adverse reactions. CORNEAL THICKNESS

516

One of the concerns of m yopia correction by corneal molding is the thllu1.ing of central epithelium of the cornea induced by a direct compression of the optical zone. As it happened in the radial kera totomy or intastromal corneal rings procedures, we think that it is possible to bring on a central flattening, working in the periphery of the cornea and we designed a lens geometry that would aid the displacement of peripheral epithe li um to wards the optical zone. Our biomechanical hypoth esis is th at the central flatten ing might be seconda ry to a mid-peripheral s teepening, induced by a displacement of the ep ithelium that results from a p roper compression in the alignment zone of this lens. TI,e hexacurve reverse geometry lens design (ESA ortho-6) we mention above attempts to mold the periphe ry of the cornea with a minimum compression in the center of the lens. A prospectjve, consecutive study was performed to evalua te the corneal response an d central corn ea l th ickness (CCT) changes after overn ight orthokeratology by means of this customized hexa-curve reverse geometry lens in hyper-Ok gas-permeable material (Boston-XO). Twenty-eigh t eyes of 14 myopic patients (ranging from - 1.00 to -4.25 0 sph, and astigm atism up to 1.000) were enrolled in the study. Assessment criteria included uncorrected visua l acuity, best-corrected visual acuity, manifes t refract ion, ultra soun d pach ymetry, corneal topog raphy, and biomicroscopic data. Th ese data were collected at baseline, and then after one night, one week, two weeks, one month, and three months of lens wear. All the examinations were performed in the mornin g immed iately after lens removal and repeated in the evening of the same da y. An ultrasound pachymete r (Allergan Humphrey model 850, Carl Zeiss Meditec, Dublin, CAl, using a velocity of 1640 m is, was used to measure central corneal thic kness. The results of this study showed th at th e cornea responded rapidly with significant (p < 0.05) central cornea l flattening and inlprovement in visual acuity after the first night o f contac t lens wear. By the end of one week, all cornea l and visual changes had reached a maximal level and remained stable during the day. These changes were sustained at the following visits. After the first molding, the fluorescein pattern showed a clearance under the center of the lens that demonstrated a minimal cen tral tOllch. Biomicroscopy showed

OrthokerntologlJ

no significant ocular adverse events. The average pretreatment CCTwas 533 ± 31 "m. During the period of the study, ultrasound pach ymetry did not show any significant change in the central thickness of the cornea (repeated measures ANOV A: p = 0.978), both in the morning and in the evening (Bonferroni/ Dunn post- hoc test: p > 0.414). Figure 1 show the details of the difference in CCT. The lack of chan ge found in the central pachymetry data suggests that the overnight contact lens can successfull y flatten the cornea without direct compression of the center of the cornea. The absence of change in CCT during the day may exclude a masking effect due to edema. Contrary to these finding, the majority of previous studies reported that orthokeratology and corneal refractive therapy ca uses central epithelial and total corneal thi.nning. This difference could be caused by the different geometry and behavior of the lenses. These results seem to confirm the biomechanical hypothesis that the central flattening of the cornea might be achieved as secondary to a mid-peripheral steepening, induced by a displacement of the epithelium that resu lts from a proper compression in the alignment zone of this lens.

517

49 Aspheric IOls (Wavefront Based IOls) Sanjay Chaudhary (India)

Convention al sph erical IOLs (Clariflex, Acrysof, Akreos, etc.) have a positive spherical aberration, which results in reduced contrast sensitivity under mesopic and scotopic conditions. Aspheric IOLs like the Tecnis (AMO), Acrysof IQ (Alcon) and Akreos AO (B and L) minimize the spherical aberra tion resulting in improved vision. A normal corneal spherical aberration is positive, i.e. + 0.27 microns (}l1Il) ± 0.02 }lm. Tecnis h as a n egative spherical aberration of - 0.27}l1Il, AcrysofIQ -0.20}lm and Akreos AO - O.O}lm (neutral). Following is a comparison of these three different lenses. (Key words: SA-Spherical Aberration, CS -Contrast Sensitivity) UNDERSTANDING SPHERICAL ABERRATION

A spherical aberration occurs when parallel rays of light do n ot focus on one point. The central bunclle of rays may focus in front of or behind the focus of the peripheral bundle of ra ys. The refractive power in the periphery of the lens may either be too weak or (usually) too strong. When the peripheral rays of light foc us in front of the central rays, it is called positive SA, and if they focus behind the central rays, it is called negative SA. The resultin g image despite a SA might be clear, but it has less contrast than an ideal optic. SPHERICAL ABERRATIONS IN A HUMAN EYE

The human cornea has a positive SA. This means that the light entering the eye from the peripheral parts of the cornea converge more to focus in front of the rays en tering the central portion of the cornea. The SA of the cornea hardly changes during lifetime. In a 4 mm pupil, rays from th e peripheral part of the cornea are obstructed and therefore the eye would manifest w ith very little SA. If the pupil dilates to 6 mm or more, the peripheral rays also reach a focus within the eye. Such an eye w ith a co-existing large quantum of SA would experience a loss of contrast. 518

Aspheric lOLs (Wavefront Based lOLs)

,

/' ,

V Negative spherical aberration

;

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,-

;

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Positive spherical aberration

Fig. 1: Spherical abe rration (SA) in a lens system

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.

SA showing spread of light on the retina

L Retina Fig. 2: Positive SA in a normal human cornea . Peripheral rays focus in front of retina

Fig . 3: 3-0 representation of SA

51 9

Instant Clinical Diagllosis it! Opiltilalmol0/5') (Refractive SlIIogen)) In a Young Eye

The cornea of a young eye has a positive spherical aberration, which gets compensated by the negative spherical aberration of the crystalline lens. TI1ere is a young ad ult, the rays of light come to a point focus on the retina, and the contrast sensitivity is good. In the Elderly Eye

TI1e lens is grow ing over a lifetime. In the process, it gets thicker. Its refractive index also increases. So from a negative SA, w ith age it develops a positive SA. In an elderly person, the cornea has a positive SA, and the crystalline lens also has a positive SA. The two lead to an even stronger effect, grea tl y increasing the overall SA and a marked decrease in contrast. CONVENTIONAL SPHERICAL IOLs

They also have an inherent positive SA and therefore they also amplify the SA of a cornea. THE TECNIS LENS (AMO)

This is a multi piece second-generation silicon lens. It has a negative prolate surface design ed on the an terior surface of the lens and has a SA of - 0.27 "m.It has a square edged optic design. It refractive index is 1.46 and an edge thickness is 0.50 mm. It can be injected through a 2.8 mm incision with the help of an injector system. Fitting Philosophy

The lens is designed to fully correct the +ve SA of the cornea thereby enhanCing the contrast sensitivity to the maxin1um. The lens is based on the Z-sharp optic teclu1010gy. The peripheral part of the anterior surface of th e lens gets a more concave desig n and therefore neutralizes the positive SA of the peripheral cornea. Various stud ies have shown that the asphericity of the cornea is + 0.27 >'ffi with a s tandard deviation of ± 0.02. This lens has a nega ti ve SA of - 0.27 "m and targets to full y correct the to tal corneal SA of the eye. THE ACRYSOF IQ (IMAGE QUALITY) (ALCON)

This lens is a single piece hydroph obic acrylic and is a blue light filtering lens (lens is in1p regnated with yellow ch romophore). The asphericity is designed on the posterior surface of the lens by thinning the lens in the center. The lens

520

Asp/wric TO Ls (Wav efrollt Ba sed IOLs)

Fig. 4: 2-D color coding of SA

Fig . 5: Point focus on the retina as negative SA of young lens neutralizes positive SA of co rn ea

521

Instant Clinical Diagnosis in Ophthalmology (Refractive Surgery) has a -ve SA of - 0.20 )lm. It has a refractive index of 1.55, an ed ge thickness of 0.21. It can be injected through a 2.8 mm incision with the injector system. Fitting Philosophy

Studies reveal that a normal vision is best when there is a residual positive SA of +0.1 /Jm in the optical system of the eye. This lens has a - ve - 0.20 )lm SA and after neutralizing the +ve SA of the cornea (SA of + 0.27 )lm), there is still a residual +ve SA of +0.07 ± 0.02 iJffi Tanzer and Schallhorn reported that 338 Navy pilots had a mean positive spherical aberration of approximately 0.1 )lm (6.0 mm pupil) (ASCRS Symposium, May 1-5, 2004, San Diego, CAl • Levy et al (AjO, 2005) fo und that for 70 "supernormal" eyes with an UCVA 2. 20/15, the positive spherical aberration of the whole eye was 0.11 )lm ± 0.077 iJffi, with a 6.0 mm pupil. These clinical observations suggest that preserving a moderate amount of positive spherical aberration may enhance the quali ty of vision in normal pseudophakic eyes. AKREOS ADAPT AO (ADVANCED OPTIC) (BAUSCH AND LOMB)

This is a single piece hydrophilic acrylic with a square edge. Its refractive index is 1.458 (hydrated). It has an anterior and posterior aspheric surface. It neither has a positive or a negative SA, i.e. a SA of ± 0.00 )lm.1t therefore does not result in any aberration being introduced in the eye. It can be injected through a 3.0 m incision. The lens has a uniform power from the centre to the edge. This gives the lens independence from the eye's optical alignment. Therefore the image quality is not disturbed even if the lens is slightly decentered. Fitting Ph ilosophy

The aberrations present in a human eye differ from person to person. Therefore an aspheric lens, which is aberration neutral, offers control of SA, which is independent of the patient's profile. Th is implies tha t the other lens manufacturers assume that the corneal SA is + 0.27 ± 0.02 iJffi in all cases. Some studies show that the variation may be even more. Therefore, if the corneal +ve SA were less than the amount assumed, these lenses wo uld result in an overall-ve SA that is worse. The best situation would be not to have a +ve SA of a conventional lens, and at the same time avoid disturbing the SA of the cornea. This opinion is supported by the Bell curve which shows that only 68 522 % of the human cornea's fall in the bracket of a standard +ve SA.

Aspheric rOLs (Wavefrout Based lOLs) ...

~

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Fig. 7: The +ve SA of an ageing lens com pounds the +ve SA on the cornea

Young eye

Ageing eye

Fig. 8: Reduced contrast sensitivity during the day (Courtesy AMO)

523

Instant Clinical Diagnosis in OphtlwlmolopJ (Refractive SlIrgenJ) Comparison of Aspheric IOLs 6.0mm Pupil size

524

Lens

Sperica/ Aberration

Residual Spherical

Aberration

AcrySof IQ

- 0.20

~m

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~m

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Aspheric 10Ls (Wavefront Based 10Ls)

Fig . 9: Glare and Halos at night (Courtesy AMO)

Fig . 10: The +ve SA of conventional IOL add to SA of corn ea

Fig. 11: The Tecn is lens

525

Instant Clill ical Diagnosis in Oplltllnlmol0:5'J (Refractive Surgery)

•r

Z-sharp optic

-;;;])25>0 L •

Z-sharp optic technology

Fig . 12: The -ve SA on the anterior surface compen sates for the +ve SA of cornea

Fig. 13: The Aerysof 10

526

Aspheric l OLs (Wavefrollt Based lOLs)

Fig . 14: The Akreos Adapt AO (Bausch and Lomb)

21 dpt

21 dpt

= dp

21 dpt

Fig. 15: Uniform power of the Akreos AO from center to edge

68%

Bell curve

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+/~

one standard deviation is only 68% of patients!

Fig. 16: Bell curve showing the variation in the corneal SA

527

50 Dual Optic Accommodative IOls GU Auffarth (Germany)

The last step in successful cataract or lens removal surgery is the restoration of accommodation. Several single-optic systems have been in troduced on the market. In Germany the ICU IOL man ufactured by Human optics AG (Erlangen, Germany) came on the market as single optic TOL based on Paten ts by Hanna. Several studies in Europe have shown certain limitations for th ese TOLs based on the anterior shift principle. Those lenses need movements of around 1.5 to 2.5 mm to achieve 3 diopters of accommodation. Even though the lens showed satisfactory clinical results, the amount of accommodation measured never exceeded 0.75 to 1 diopter, indicatin g a big range of pseudoaccommodative parameters (such as residual refraction , myopia, astigmatism, pinhole effect of pupil, corneal refractive changes, etc.). On the US-Market the Crystalens AT 45 was actually FDA approved and widely u sed. Apart from visual acuity results no objectiv e means for accommodative measurements were presented in the peer reviewed literature. Studies in Europe by Find\. and coworkers indicate a similar performance of this sinfle optic l OL like the l eU. A dual-optic design offers potential advantages over single-optic designs in that less lens movement is necessary with the dual optic to achieve a certain amount of accommodation. For example, in order to ach ieve 2.0 D of pseudoaccommodation, a 22 D single-op tic IOL w ould need to move forward 1.6 mm within the capsular bag. A dual-optic 10L with a +30 D front lens and a -8 D posterior lens (overall power = 22 D) would only require 0.8 nun of separation to achieve 2.0 0 of power change. Two dual optic IOLs are curren tly tested. The Sarfa razi Elliptical Accommodating IOL and the Visiogen Synchrony len s. Both utilize a pluspowered biconvex front lens connected to a negatively powered concave-convex lens. During the accommodative effort the two lens componen ts increase their distance fro m each other, resulting in increased effective power of the overall lens. The Sa rfa rzi TOL is now unde r evaluation by Bausch and Lomb. No clinical data h ave been presented so fa r. The Visiogen Synchrony accommodative IOL consists of a high power (30 D ptr.) anterior optic and a variable minus pow er posterior optic. It is made of Silicone material. Implantation of the first generation models were done with 528 folding forcep s. The latest generation h as now an injector for implantation.

50 Dual Optic Accommodative IOLs GU Auffarth (Germany)

The last step in successful cataract or lens remo val surgery is the restoration of accommodation. Several single-optic systems have been in troduced on the market. In Germany the lCU IOLmanufactured by Human optics AG (Erlangen, Germany) carne on the market as single optic IOL based on Patents by Hanna. Several studies in Europe have sh own certain limitations for these 10Ls based on the anterior shift principle. Those lenses need movements of around 1.5 to 2.5 mm to achieve 3 diopters of accommodation . Even though the lens showed satisfactory clinical results, the amount of accommodation measured never exceeded 0.75 to 1 diopter, indicating a big range of pseudoacconunodative parameters (such as residual refraction, myopia, astigmatism, pinhole effect of pupil, corneal refractive changes, etc.). O n the US-Market the Crys talens AT 45 was actually FDA approved and w idely used. Apart from visual acuity results no objective means for accommodative measurements were presen ted in the peer reviewed literatu re. Studies in Europe by Find!. and cowo rkers indicate a similar performance of this sinfle optic IOL like the lCU . A dual-optic design offers potential advantages over single-optic designs in that less lens movement is necessary w ith the dual optic to ach ieve a certain amoun t of accommodation. For exam pi er in order to ach ieve 2.0 0 of pseudoaccommodation, a 22 D single-optic IOL would need to move forward 1.6 mm within the capsular bag. A dual-optic IOL with a +30 0 front lens and a -8 D posterior lens (overall power = 22 0) would only require 0.8 mm of separation to achieve 2.0 D of power change. Two d ual optic 10Ls are currently tested. The Sarfarazi Elliptical Accommodating IOL and the Visiogen Synchrony lens. Both utilize a pluspowered biconvex front lens connected to a negatively powered concave-convex

lens. During the accommodative effort the two lens components increase their distance from each other, resulting in increased effective power of the overall lens. The Sarfarzi TOL is now under evaluation by Bausch and Lomb. No clinical da ta ha ve been presen ted so far. The Visiogen Synchrony accommodative TOL consists of a high power (30 D plr.) anterior optic and a variable minus power posterior optic. It is made of Siticone ma terial. Im plantation of the first generation models were done with 528 folding forceps. The latest generation has now an injector for implantation.

Dual Optic Accommodative rOLs Synchron y TM Accommodative tOL Synchrony vs single-optic accommodative tOL

~ 8 0 15. 7 .Q

c

6 5

;;;

4

£ .Q

Synchrony-dual optic system

./

./ ./ ./

"E0

.-.- -.-

--_.-'

3 ./ E 2 ~ c=, _ ,- ·- · - Single. optic accommodative IOL 8u 1 ~ - . - . 0 0.0 0 .5 1.0 1.5 2.0 2.5 3.0 Anterior movement of tOl (mm)

'"

Fig . 1: Graphical illustration of the accommo-

dative effect in relation to amount of optic shift of single and dual optic systems

Fig. 2. Clinical retroillumination photograph and still picture of the Synchrony tOl

Fig. 3: Injektor system for Synchrony tOL 2 years follow-up: Synchrony TM Accommodative tOL

1 Month

12 Months

Fig. 4

24 Months

529

Instant Clinical Diagnosis in OplttltalmologtJ (Refra ctive Surgery)

The Synchrony IOL as been extensively studies in laboratory (rabbit) models as well as in mul ticenter clinical trials in Europe and Latin America. Clinical data are avai lable with a 3-4 years follow u p now. The lens is also now CEmarked in Europe and therefore available for clinical use. The first clinical generation of the Synchrony dual optic accommodative IOL showed over a 2-3 years follow up period good fu nctional results, stable refrac tion and low to mediocre PCO development. lnterlenticular opacification (ILO) was the main concern regarding these dual-optic IOLs. To date, however, this has not been reported as a complication of these [O Ls. Studies of the IOL in rabbits suggest that the design features of the Synchrony may help prevent posterior and anterior capsule fibrosis. In another stud y in rabbits the incidence of [LO was zero, also ind icating that the lens material (silicone) ma y prevent interlen ticular lens epithelial cell migration. Ossma and coworkers could demonstrate by ultrasoun d biomicroscopy movements between the two IOLs of upto 0.6 to 0.8 mm . The residual near addition to reach) l was around 0.78 diop ters and UDVA and UNV A was in all cases >20 / 40. Dick et al and Auffar th et al presented si milar results with the early Synchrony model. In contrast to single optic designs the d ua I optic designs offer theoretically and practically the chance of a real accommodative effect. Several questions still need to be scientifically evaluated. The IOL calculation or in other words the exact location of the IOL in side the capsular bag is difficult to pred ict o r to determine. The preven ti on of posterior capsule opacifica tion (PCO) is still a longterm concern. New instruments such as the "perfect capsule" system by Milvella Inc (Sydney, Australia) offer nowadays new means to target the elimination of lens epithelia l cells (LEC). In summa ry the dual optic TOLs seem to be the most effecti ve design or [OL type achieving a significant amoun t of accommod ation. Other (new) concepts in accommod ative IOLs includ e the Powervision Fluidvision IOL, which is capa ble of curvarture changes to achieve accommodative changes or the smart lens, a lens refilling device consisting of a thermoplas tic material. ew clinica l studies espeCially with the now clinically approved Visiogen Synchrony IOL will show how successfu l these dual optic designs on the marke t w ill be.

530

Instant Clinical Diagnosis in OphthalmologtJ (Refractive Surgery)

The Synchrony IOL as been extensively studies in laboratory (rabbit) models as well as in multicenter clinical trials in Europe and Latin America. Clinical data are ava ilable with a 3-4 years follow up now. The lens is also now CEmarked in Europe and therefore available for clinical use. The first clinical generation of the Synchrony dual optic accommodative IOL showed over a 2-3 years follow up period good functiona l resuits, stable refraction and low to mediocre PCO development. Interlenticular opacification (ILO) was the main concemregarding these dual-optic IOLs. To date, however, this has not been reported as a complication of these IOLs. Studies of the IOL in rabbits suggest that the design features of the Synchrony may help prevent posterior and anterior capsule fibrosis. In another stud y in rabbits the incidence of ILO was zero, also indicating that the lens material (si licone) ma y prevent interlenticular lens epithelial cell migration. Ossma and coworkers could demonstrate by ultrasound biomicroscopy movements between the two TOLs of upto 0.6 to 0.8 mm. The residual near add ition to reach)1 was around 0.78 diopters and UDVA and UNV A was in all cases >20/40. Dick et al and Auffarth et al presented similar results with the early Synchrony model. Tn contrast to single optic designs the dual optic designs offer theoretically and practically the chance of a real accommodative effect. Several questions still need to be scientifically evaluated. The IOL calculation or in other words the exact location of the IOL inside the capsular bag is difficult to predict or to determine. The prevention of posterior capsule opacifica tion (PCO) is still a longterm concern. New instruments such as the "perfect ca psu le" system by Milvella Inc (Sydney, Aust ralia) offer nowadays new means to target the elimination of lens epithelial cells (LEC). In su mmary the dual optic TOLs seem to be the most effective design or IOL type ach ieving a significant amount of accommodation. Other (new) concepts in accommodative IOLs include the Powervision Fluidvision IOL, which is ca pable of curvarture changes to achieve accommodative changes or the smart lens, a lens refilling device consisting of a thermoplastic material. New clinica l studies especially with the now clinically approved Visiogen Synchrony IOL will show how successful these dual optic designs on the market will be.

530

Dual Optic Accommodative lOLs 2 Years Follow up : Sync hrony TMAccommodative IOl

Fig. 5 Figs 4 and 5: Retroillumination photograph of Syn-chrony IOLs with a 24 months follow-up_ Only small amount of pee, no ILO

0 .59 mm

Fig. 6 UBM : Pat. LBB. 6 Mon. postop

0 .80 mm

Fig. 7 Figs 6 and 7: Ultrasound biomicroscopy of Synch rony IOL indicating movement between lenses of 0.59 (Fig. 6) and 0.80 mm (Fig. 7)

531

51 Anterior Chamber Phakic IOl with Angle Fixation Juan C Rocco (Argentina)

ADVANTAGES The va lidity of the concept of a myopic implant has been proven by 30 years of experience with the Kelman's multiflex implant. owadays we have near of 20 yea rs of use of the first Baikoff model and a lot of happy ex-high myopic patients. With these teclmiques we have a lot of advantages like: excellent visual results; fast visual recovery; preserva tion of accommodation; easy operation

teclmique to anterior chamber surgeon; reverSibility; the possibili ty to combine with excimer laser surgery in very high m yopic patients; the option to correct

astigmatism with the phakic IOL and the predictability of visual result. Since the stan dard deviation of the residual postoperative refracti on is in nea r one d iopter, in almost all the patients, which appears to be the best of all the refractive surgical techniques and also is a very reproducible surgery. In the past there was concern about the long-term potential damage to anterior chamber structures, meanly the endothelial loss, but with the new lens design are safer and this proble m is almost disappea r. In these last years we can see a lot of very good result and with a precise technique is a very useful

options for patients with high myopia.

HISTORY The use of anterior chamber lens to correct myopia was developed first time in 1950s by Strampelli et al and Barraquer and Choyce et aI, also Feclmer and colleagues with the "Worst-Fechner iris claw" and Praeger and Baikoff, all of them collaborated to develop this option fo r high myopic patients. After tha t joly in 1987 modified the Kelman Multiflex four-point fixations lens that was used to ca taract surge ry and now it is used in anterior chamber

to correct high myopia. The first generation of this kind of lens to correct myopia was designed by Dr George Baikoff and the Company Domilens in France, and was called Balkoff ZB Lens. This was a Z shaped haptic derived from the Kelman 's Multiflex type, 532 which a!Jows a certau) suppleness of the lens that can adap t to the different

Anterior Chamber PhakicIOL with Angle Fixation

Fig. 1: Kelman's multiflex implant

Fig. 2. Anterior chamber phakic IOL angle fixations

533

InstnlltClillicni Dingllosis ill Opl/tlwllllology (Refractive Surgenj ! dimensions o f the an terior chamber. The foolplates we re too large to avoid the iris wrapping. This model was designed with 25 degree vaulting to p roject in front and very near of pupil and have to maintain a distance abo ut 2 mm back from the central cornea and about 1 nun U1 front of the p upil. Its optic was 4.50 mm and the thickness of the ed ges is 0.7 mm. There was a lot of complications w ith this model, mainly a high ra te of endothelial loss because an excessive con tact between the optic ed ge and the peripheral endothelium . Baikoff realized of this problem and modificated the angle of the lens and was born the new model Z B5M, to reduce the contac t between the lens and the pe rip heral epithelium and ga ined 0.6 mm of space between the cornea and the lens, in comparation with the ZB lens. The first model has to be explan ted in several patients for high rate of endotheli al loss, but the last model was safer and pred icable because the loss of endothelial cells occurs only m ainly during the opera tion, but the first model the endothelial loss appeared during and after the surgery. TYPES OF PHAKlC LENS

Marcher GMBH 93 A

• Plano Concave

• • • • • • •

PMMA UV Ra ys Block Length: 12.50 to 13.00 mm Posterior Angle 19 0 Optic Size: 5.50 mm Diopters Range: - 6.00 to - 22.00 d iopters Compan y: Marcher Gm bH

Baikoff Model ZB5MF • Biconcave

• • • • • • •

PMMA UV Rays Block Length: 12.50 mm - 13.00 mm - 13.50 nun Posterior angle 200 Optic Size: 5 mm Diopte rs Ra nge: 7.00 d iopters to - 20.00 d iopters Company: Domilens

Phakic 6 Model 130 534

• Biconcave • PMMA

Allterior Chamber Phakic lOL with Angle Fixatioll

Fig. 3: Anterior chamber phakic IOL in high myopia case

Fig . 4: Worst Fechne r iris claw lens

535

Instant Clinical Diagnosis in Oplr tlwlmologtJ (Refractive SlIrgenJ)

• • • • • •

UVBlock Length: 12.00 rnm to 14.00 mm Posterior angle 14° Optic Size : 6 mm Diopters Range: - 2.00 diopters to - 25.00 diopters Company: Ophthalmic Innovations Internationa l Inc.

Nuvita Baikoff MA 20 • Biconcave

• • • • • •

PMMA UV Block Length: 12.50 rnm to l3.50 mm Optic Size : 4.50 diopter Diopter Range: From - 7.00 diopters to - 20.00 diop ters Company: Bausch and Lomb.

Kelmnan Duet

• • • • • • •

Two piece

H aptic PMMA Optic foldable Length: 12.00 rnm - 13.00 mm - 13.50 rnm Optic Size: 5.50 rnm Diopter Range from - 8.00 diopters to -20.00 diopters. Compan y: Tekia, Inc.

INCLUSION CRITERIA

The selection process must be very strict and the patients must have real expectative before surgery. The patient will be refraction stable at last 8 month; older than 21 years old, has a m yopia between - 4.00 diopters to - 22.00 diopters; has problem w ith using contact lens; can not wear spectacles (for a physic appearance 0 work restriction); endothelial cell density greater than 2.500 cell / m m; an terior chamber depther than 3.4 rnm; without any eye disease ~ke: glaucoma, uveitis, retinal detaclunent, conjW1ctivitis, autoimmune disease; any retinal problem must be treated before the surgery (retinal photocoagulation). Before surgery we need know exact manifest and cyclopegic refraction, visual acuity, slit lamp examination, d irect and indirect ophthalmoscopy, oecular pressure, pupil diameter. SURGICAL TECHNIQUE

The patient has to firm informed consent.

536

Anterior Chamber Phakic l OL with Angle Fixation

-r-----::._;=-- - - - -

g

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