Primary Angle-Closure and Angle-Closure Glaucoma

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PrimaryAngleClosure_def

20-06-2007

14:10

Pagina 1

Primary Angle-Closure and Angle-Closure Glaucoma


S.V. Kessing and J.Thygesen

by Svend Vedel Kessing and John Thygesen

Kugler Publications, Amsterdam, The Netherlands

Table of Contents

I

Primary angle-closure and angle-closure glaucoma by Svend Vedel Kessing and John Thygesen

Kugler Publications/The Hague/The Netherlands

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II

Table of Contents

ISBN 10: 90-6299-211-0 ISBN 13: 978-90-6299-211-9

Distributors: For the U.S.A. and Canada: Pathway Book Service 4 White Brook Road Gilsum, WH 03448 U.S.A. email: [email protected] For all other countries: Kugler Publications P.O. Box 20538 1001 NM Amsterdam, The Netherlands Telefax (+31.20) 68 47 788 website: www.kuglerpublications.com

© Copyright 2007 Kugler Publications All rights reserved. No part of this book may be translated or reproduced in any form by print, photoprint, microfilm, or any other means without prior written permission of the publisher. Kugler Publications is an imprint of SPB Academic Publishing bv, P.O. Box 20538 1001 NM Amsterdam, The Netherlands

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Table of Contents

III

TABLE OF CONTENTS

Preface By Svend Vedel Kessing and John Thygesen Introduction Aims And Methods

VII

1 1

Detection of Primary Angle-closure (PAC) Limbal Chamber Depth Measurement (LCD) Methodology Sources of Error

7 7 7 10

Diagnostic Methods in PAC Axial Chamber Depth Measurement (ACD) Methodology Optical Pachymetry Ultrasonic or Laser Based Chamber Depth Measurement Laser Scanning Pachymetry (Visante Oct System) Sources of Error Gonioscopy Introduction Goniolenses and Their Uses Posner’s 4-mirror Indentation Lens Goldmann’s Gonioscopy Lens Gonioscopy Methods with PAC Chamber Angle: Classification and Definitions Standardised PAC Gonioscopy Methodology Start the Examination with the Posner Lens 4-mirror Lens Continuation with Goldmann’s Gonioscopy Lens Gonioscopy Findings Normal Anatomy of the Chamber Angle Glaucoma Pathology in the Chamber Angle Provocation Test Dark-room Test – Prone Position Ultrasound Biomicroscopy (UBM)

11 11 13 13 14 15 16 16 16 17 18 23 25 25 29

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30 32 32 32 41 45 45 46

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IV

Table of Contents

Main Classification of PAC Introduction Main Classification and Methods of Classification Main Groups and Subclassification of PAC Group I: PAC with Pupil Block Pathophysiology and Pathogenesis Detection and Diagnosis Subclassification with Specific Treatment and Case Histories YAG-laser Iridotomy: Evaluation YAG-laser Iridotomy in General Group II: PAC with Plateau Iris Pathophysiology and Pathogenesis Detection and Diagnosis Subclassification with Specific Treatment and Case Histories Argon-laser Iridoplasty: Evaluation Argon-laser Iridoplasty in General Group III: PAC Mixed Group (I+II) Pathophysiolology and Pathogenesis Detection and Diagnosis Subclassification with Specific Treatment and Case Reports YAG-laser Iridotomy/argon-laser Iridoplasty: Evaluation YAG-laser Iridotomy/argon-laser Iridoplasty In General Treatment Procedures with PAC By J. Thygesen Principles of Treatment with Acute PAC I, II and III Treatment of Acute PAC I, II and III (Previously “Acute Glaucoma”) YAG-laser Iridotomy Indications Contraindications Technique26 Argon-laser Iridoplasty Indications Relative Iridoplasty Indications Contraindications Technique Fistulating Operation Indication

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49 49 50 55 55 55 57 58 67 69 70 71 73 75 80 83 84 84 84 85 91 93 95 95 96 100 100 100 101 102 103 104 104 104 105 106

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Table of Contents

Complications Prevention of Post-operative Hyperfistulation Post-operative Treatment

V

106 107 107

References

109

Rights of illustrations

112

Index

113

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VI

Table of Contents

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Preface

VII

PREFACE

The objective of this book is to offer the general ophthalmologists a clinical comprehensive and practical guidance manual for primary angle-closure and primary angle-closure glaucoma to be used in the daily clinical work. Already in the nineteen seventies our Danish colleague, Poul Helge Alsbirk documented the exceptional high prevalence of angle-closure glaucoma among the Eskimo or Inuit population in Greenland, a North-Atlantic part of Denmark. As Danish ophthalmologists ever since have been responsible for the diagnostics and therapy of primary angle-closure (PAC) and primary angle closure glaucoma (PACG) among these patients, this has led to a profound clinical experience and a growing knowledge of the complicated nature of this entity. We have experienced that the sub-clinical asymptomatic, “creeping” angle closure is a common type and early detection and prevention therefore necessary, just as in open-angle glaucoma. Further that different mechanisms and stages of PAC need different treatments and that a new, more differentiated and objectively based classification and terminology consequently has to be developed. To practice these recommendations we have learnt to use a number of standardised, clinical diagnostic methods. To support the Danish ophthalmologists a guidance manual for primary angle-closure in Danish was published 2003 based on our long clinical experience, the present evidence based literature and conferences on glaucoma. As the guidelines in Danish were very well received we were encouraged to produce an updated English edition. The new evidence about the high prevalence of angle-closure in Asians further supports an English edition. The point that early angle-closure may be cured and the fact that the world-wide visual disability from this disease is almost equivalent to open-angle glaucoma emphasizes the “urgent need” of improving the angle-closure management. The word “glaucoma” is now only used in the presence of structural defects of the optic nerve head or when visual field defects are found.

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VIII

Preface

Acknowledgment should be given to our Danish colleagues Poul Helge Alsbirk, Erik Krogh and Lisbeth Serup for their advice and guidance of crucial importance. A special thank goes to Pfizer Denmark, who published the first edition in Danish and sponsored the translation from Danish into English with an unrestricted educational grant. Copenhagen May 2007 Svend Vedel Kessing and John Thygesen

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Introduction 1

INTRODUCTION AIMS AND METHODS In February 1997, the Danish Glaucoma Society published a book of guidance describing the classification, diagnostics and treatment of primary open-angle glaucoma (POAG)21. The present book has been published as an attempt to provide a similar guidance manual for primary angle-closure glaucoma and its preliminary stages. The first edition in Danish was already published in 2003 and the contents of the present book in English are the same, with few updates. In 1998, the European Glaucoma Society published their first edition of Guidelines for Glaucoma and in 2003 the second edition, in which the subject of primary angle-closure glaucoma was also treated. However, the present book suggests a more radical, well-defined and systematic treatment procedure, which in certain substantial areas proposes innovative thinking, to a great extent based on the personal clinical experience and attitude of the authors. Throughout the book, the term ‘glaucoma’ will only be used when the observed development stage of angle-closure is incurable, i.e in connection with permanently increased intraocular pressure (IOP) due to peripheral anterior synechiae (PAS), latent glaucoma; and increased IOP together with the classical structural/functional glaucoma defects, manifest glaucoma. In principle, this is similar to POAG21. Furthermore, the Anglo-Saxon term ‘primary angle-closure’ (PAC) will be used. Due to these terminological changes, a successfully treated case of acute PAC without subsequent complications in the form of permanently increased eye pressure or structural/functional glaucoma defects will not, as was previously the case, be classified as being ‘acute glaucoma’. Obviously, this is an undisputed advantage to the patient in question since it provides the opportunity of declaring that the patient has been cured and does not indeed have glaucoma. By not labelling the patient as having a glaucoma diagnosis, the quality of life of the patient will remain

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2

Introduction

unaffected, as will any personal insurance policies. For the same reason, it is an advantage that the previously used term ‘latent angle-closure glaucoma’ (oc-cludable angle) has now been replaced by the term ‘imminent (threatening) PAC because of the high risk of developing acute or chronic PAC. Such a patient, following subacute laser treatment, is ensured against the development of not only an angle-closure attack, but also against the development of glaucoma as defined above. It should be noted that there seems to be a tendency for researchers around the world to change the terminology used to describe the subject of PAC along the same lines as noted above28, 29 although this is not yet generally accepted. It is with this in mind that the above-mentioned terminology has been deliberately chosen for the purpose of outlining the systematic treatment procedures described in this book. The two main purposes of the PAC-treatment procedures are: – To contribute towards well-motivated preventive treatment of the various forms of imminent PAC in order to avoid both the acute catastrophe and the more common, asymptomatic, “creeping” angle-closure17, 34, 35. – To contribute towards an optimal course of treatment for the individual patient by applying specific treatment. With regard to the first purpose in question, it can be stated that the treatment strategies around the world – even those found in the most recent guidelines concerning PAC28, 29 – first and foremost deal with the prevention of manifest PAC glaucoma in order to prevent loss of vision. The point in question is that the acute PAC attack will diagnose itself and only seldom lead to loss of vision; thus any detection and preventive treatment is deemed unnecessary. But this negative attitude to PAC detection implies that prevention of the most common type of PAC glaucoma, the asymptomatic, “creeping” form34, 35, is missed. This is especially serious, as the visual loss due to the asymptomatic form seems to be greater than that of the acute PAC41. Furthermore, a simple and functional method for detecting PAC (limbal chamber depth (LCD) evaluation) does exist, as well as

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Introduction 3

adequate and uncomplicated preventive treatment procedures (YAG iridotomy and laser iridoplasty). The basic requirements for the detection and prevention of imminent PAC are therefore available. A more general recommendation will, however, require a well-defined, standardised PAC examination protocol with regard to both professionally and ethically clear and acceptable indications for treatment. In this book, this requirement is met through the use of combined diagnostic PAC methods (standardised PAC gonioscopy and axial anterior chamber depth (AACD)) besides the generally applied glaucoma examinations (Goldmann’s applanation tonometer, ophthalmoscopy and automatic perimetry). It should be noted that both of the international PAC guidelines mentioned above are inconsistent in their rejection of preventive treatment of imminent PAC in that they, in spite of this attitude, recommend preventive laser treatment in some not clearly defined conditions. This suggests a tendency towards a change in the international outlook. It is also worth mentioning that apart from these official guidelines, there are a few well-documented studies which do recommend preventive iridotomy. These are described in the chapter: YAG-laser iridotomy: Evaluation (p. 67). Detective, preventive treatment of imminent PAC should, of course, be carried out in the primary ophthalmological health sector, and the practical possibilities for doing so are to a great extent already present. For instance, approx. 2000 YAG-laser iridotomies per year were registered in Denmark during the period between 1996 and 1998 of which 800 were carried out within the framework of private practice settings. However, it is uncertain how many of these laser treatments were carried because of imminent PAC. The second purpose of the PAC-treatment procedure: An optimal course of treatment for the individual patient may to a great extent be gained by applying a specific treatment. This is defined as a treatment which, guided by the findings from the initial objective examina-tion, is adapted to the observed specific type of pathoanatomy and PAC development stage of each individual eye. The opposite of this, i.e. unspecified treatment, may be described as the “trial and error” method in which the different treatment

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4

Introduction

procedures are tested successively, often leading to considerable and understandable frustration for the patient. It should be noted that the “trial and error” method is still recommended in connection with one of the above-mentioned official international guidelines29. Whereas the other guideline28 suggests a procedure which in some respects is similar to the present specific treatment. But in a recent review the same authors emphasize the need for a new PAC treatment procedure based on the same principles as the present specific treatment35. Therefore, also in this matter, there is a tendency towards a changing international outlook. In order to simplify the prescription of a specific treatment, we use a standardised, objec-tively based identical subclassification (staging) of each of the three main PAC forms so that a specific, recommendable treatment with an expected satisfactory effect is attached to each clinical entity. In this way, it is possible to work out a concise flow chart for specific treatment of PAC (fig. 19), which can be used in the busy daily clinical world. This flow chart, together with the diagram showing the standardised PAC gonioscopy method (fig. 11), involves the essence of the systematic PAC-treatment procedures and will therefore hopefully be found on the notice board at eye clinics in the future. It must be stressed that the above-mentioned classification is thus only based on objective findings and not – as is the case of the prevailing method of classification – based on both subjective symptoms and objective signs. In order to demonstrate the importance of specific treatment, case reports containing examples of unspecific treatment with regard to causes and consequences have been inserted in relation to each individual clinical subgroup. In connection with each case report, the concluding and final examination at the Glaucoma Clinic, Copenhagen University Hospital, has been carried out using the specified systematic PAC procedure in order to demonstrate the applicability of the recommendations. With regard to the occurrence of PAC, the prevalence of manifest PAC glaucoma among persons over 40 years of age was found to be 0.6% (women: 0.9%, men: 0.2%) in a population glaucoma study carried out in Northern Italy in 200034. This number is higher than

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Introduction 5

numbers found in earlier studies in Europe and North America and does not even include the early stages of PAC without structural and/or functional glaucoma defects. Therefore, it may be concluded that the occurrence of PAC in Europe seems to be higher than previously assumed. Moreover new population studies show that the prevalence of manifest PAC glaucoma in Asians and Indians is about the same as or higher than the prevalence of POAG, and that the world-wide visual disability from PAC glaucoma is proportionately greater than that from POAG30, 40. All in all, according to the opinion of the authors, there is a need for clarifying PAC recommendations with the purpose of further improving PAC treatment. As has been mentioned several times, similar tendencies can be detected internationally. The present guidelines should neither be regarded as being fixed rules nor as representing a general consensus, with possibilities for medicolegal sanctions! Rather, the guidelines should be seen as suggestions based on the personal experiences of the authors gained through their everyday clinical lives, conferences on glaucoma and the present literature. Therefore, there is no solid scientific documentation for all the opinions and guidelines put forward in this book. Consequently the next step should be to carry out controlled studies, possibly based on the present clinical treatment procedure.

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6

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Introduction

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Detection of primary angle-closure (PAC) 7

DETECTION OF PRIMARY ANGLE-CLOSURE (PAC)

Since the development of Goldmann’s applanation tonometry method in 1955, traditional glaucoma detection has consisted of intraocular pressure (IOP) measurement. Today, in the case of POAG, it is generally accepted that IOP screening has an unacceptably low sensitivity and specificity. Assessment with regard to structural glaucoma changes in the nerve head and nerve fibre layer21 is more specific and should be used. With regard to PAC, it is equally important to stress the fact that detection by means of IOP measurement alone is of no value since the early cases (of PAC) will remain undetected, and consequently prevention of the most common PAC glaucoma, the asymptomatic, “creeping” form34, 35, will not be provided. As the visual loss due to PAC especially seems to be caused by this form, there has been a call for early detection of the asymptomatic PAC41. It is, however, becoming generally accepted that limbal chamber depth assessment by means of a slit lamp is the preferred method for detection of PAC31, 32, 38. This assessment should therefore be routinely used in the clinic on all first visit patients.

LIMBAL CHAMBER DEPTH MEASUREMENT (LCD) The limbal chamber depth assessment was introduced by van Herick, Schaffer & Schwartz as early as in 19691, however the routine use of the method as a means of detecting PAC at an early stage has not yet found general acceptance. Methodology The temporal corneal area immediately central to the sclerocorneal junction zone is observed with a high slit lamp magnification and a narrow vertical slit. The angle of the light must be approximately perpendicular to the corneal surface, and the slit lamp microscope must be placed at an angle of approx. 45-60 degrees (not

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8

Detection of primary angle-closure (PAC)

decisive) from the source of light (fig. 1). In the optical section of the peripheral chamber angle, the examiner can now assess the distance between the anterior surface of the iris and the posterior corneal surface and relate this to the size of the peripheral corneal thickness (CT). An iris/corneal distance of 1/4 (LCD = 0.25) of the peripheral corneal thickness arouses the suspicion of a narrow angle (fig. 2), whereas LCD < 0.25 usually indicates PAC. However, in both cases there is a clear indication for subsequent gonioscopy. Conversely, LCD > 0.5 normally excludes PAC.

Fig. 1. Limbal chamber depth (LCD) measurement based on van Herick’s test.

These values regarding LCD assessment are generally accepted as being practically applicable for the routine clinical detection of PAC31, 32. For instance, using a limit value of 0.25 in a population study carried out in Mongolia32, the sensitivity and specificity of the LCD method were set at 99% and 66%, respectively, whereas in a population study carried out in Northern Italy, the sensitivity and specificity were set at 88% and 17%, respectively. Practically all narrow angle systems are thus detected, although at the

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Detection of primary angle-closure (PAC) 9

expense of a few too many false positives (specificity 66% and 17%). However, LCD assessment is clearly an acceptable method of detection, especially when considering its simplicity and the speed of implementation of the method. It should be stressed that the surface of the iris root, as is well known, is by no means level, but has an undulating outline concentric with the limbus in which the “crest” of the iris should normally form the basis for the classification (fig. 2). Thus, the LCD measurement is the result of a subjective assessment, which is why standardised PAC gonioscopy and axial chamber depth measurement are the diagnostic examinations of choice in the evaluation of suspected PAC.

a

b

Fig. 2. Limbal chamber depth assessment. a: Positive test (LCD = 0.25). b: Negative test (LCD = 1.0)

Finally, it should be noted that the above-mentioned guidelines for interpreting the LCD method first and foremost apply to the most frequent forms of pupil block PAC in that LCD in the much more seldom pure plateau iris condition lies between 0.25 and 0.5 (ref: Group II: PAC with plateau iris). There is a risk of a false negative LCD interpretation with plateau iris. Therefore, for correct detection of pure plateau iris it is essential that routine use

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10

Detection of primary angle-closure (PAC)

of the quickly performed gonioscopy procedure using a Posner lens be carried out, even with the slightest suspicion of PAC with a LCD evaluation around 0.25. Sources of error As mentioned, the LCD determination is simple and easy to implement. The safe use of the method does, of course, require some clinical experience. The sclerocorneal peripheral area may sometimes, especially among elderly people, be indistinct due to limbal corneal changes (arcus senilis, marginal scarring). Furthermore, the location of the sclerocorneal peripheral area compared to the chamber angle may vary because of normal anatomical variations of the insertion of the cornea into the sclera. Normally, the superficial scleral lip is the longest and covers the angle anatomy. However, quite often temporally the superficial scleral lip is shorter than the deeper one (partial limbal scleral staphyloma2), and this may create a false positive LCD assessment. This is due to the fact that in this situation the sclerocorneal peripheral area is closer to the tip of the angle, and thus the LCD measurement is carried out rather more peripherally where there is a reduced space to the iris. This normal anatomical variant is often seen in combination with embryotoxon posterior (ref: Schwalbe’s line, the normal anatomy of the chamber angle).

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Diagnostic methods in PAC 11

DIAGNOSTIC METHODS IN PAC AXIAL CHAMBER DEPTH MEASUREMENT (ACD) As mentioned in the introduction and appears in the chapters concerning the Main Classification as well as the Main Groups and subclassification of PAC, almost as much attention will be paid to axial chamber depth measurement as to gonioscopy. In the most recent guidance manuals on PAC treatment28,29 this stress on the routine clinical application of ACD measurement is not to be found, even though it now is well recognised that a small ACD is a significant predictor of PAS42. In this book there are, however, several explanations as to why the use of ACD measurement is so strongly recommended. The examination may be used as a reasonably reliable and rapid supplement to the somewhat more complicated gonioscopy, especially with regard to early PAC diagnosis and the indication for preventive treatment. In such a situation, gonioscopy is often difficult, whereas ACD measurement is easy to perform. Apart from that, ACD assessment is particularly valuable with respect to proper main classification of PAC and thus for the specific treatment, which, as mentioned in the introduction, represents the second purpose of this book. Finally, the increasing use of ultrasonic examinations inclinics means that more and more ophthalmologists are able to perform ultrasonic ACD determination instead of optical pachymetry; though the latter is our primary recommendation in this book. The new laser scanning pachymetry further seems to be one of the preferred instruments in the future to measure ACD37 . Both ACD measurement and LCD determination are linked to relative pupil block (ref: Group I: PAC with pupil block, p. 55). These two measurements show a positive correlation without significant difference between the two eyes, both among healthy people and patients with PAC. According to Tørnquist3, the average ACD value with unilateral acute PAC is 1.61 mm in the acute eye and 1.77 mm in the healthy eye, whereas both values vary significantly from ACD in normal eyes (≥ 2.5 mm).

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12

Diagnostic methods in PAC

On the other hand, in the case of unilateral secondary forms of angle-closure (SAC), there is a marked difference between the ACD measurements and the LCD assessments in the two eyes. The advantage of the ACD method as opposed to the LCD assessment is that it provides an accurate quantitative estimate of the chamber depth and that this measurement does not change even after YAG-laser iridotomy, which is not the case with LCD3. Especially following preventive laser treatment, it is desirable to have case notes which include an objective and reasonably reliable indication criterion for the YAG iridotomy. As previously stated, ACD determination is of great importance in the main classification of PAC with respect to differential diagnosis between pupil block conditioned PAC and the plateau iris form. This is illustrated in the section concerning main classification of PAC and in the flow chart for specific treatment of primary angle-closure (fig. 19). As a general rule, pupil block conditioned PAC only occurs with values below 2.5 mm ACD (internal measurement) and predominantly with values ≤ 2.0 mm. Furthermore, the prevalence rate rises significantly with lower ACD values – up to 85% below 1.5 mm31. This clear, inverse relationship to the prevalence of PAC with pupil block and thereby the degree of angle narrowness means that ACD measurement is the only method that enables a quantitative, indirect estimation of the size of the chamber angle. This makes the measurement a rational supplement to the subjective gonioscopic assessment of the narrowness of the chamber angle with the pupil block form of PAC (ref: Main classification and classification methods). The relationship between the axial chamber depth and the prevalence of angle-closure does not, however, exist with purely plateau iris PAC where the angle is narrow in spite of normal ACD (≥ 2.5 mm)12. This is used in the differential diagnosis between pupil block and plateau iris PAC. As stated, the differential diagnosis between primary and secondary angle-closure forms (PAC and SAC) is further assisted by combined use of both LCD and ACD measurements. In the case of post-inflammatory absolute pupil block with iris bombé, there is a significant difference between the two eyes of the patient as regards LCD, whereas the ACD measurements are equal, i.e. there is a lack of correlation between LCD and ACD in the eye in question. In the case of ciliary block (formerly known as malignant

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glaucoma), choriodal detachment and “uveal effusion” (cyclitis annularis pseudotumerosa), forward sub-luxated lens with increased relative pupil block as well as with SAC following a central vein thrombosis, both LCD and ACD are reduced in the eye in question, i.e. there is correlation between LCD and ACD, however with a difference between the two eyes for both parameters. With this in mind, the significance of a full examination, including ACD of the “healthy” eye with regard to a difference between the eyes will be stressed many times in the following pages. Methodology Optical pachymetry The ACD measurement itself is carried out using a special attachment on a Haag-Streit slit lamp (fig. 3). The chamber depth measuring device (pachymeter II) is mounted on two steel pins on top of the microscope. The right eyepiece is exchanged for a special measuring eyepiece, and the refraction is adjusted to +6. The microscope arm is locked in place on the microscope pillar, leaving the right eyepiece at a 40 degree angle from the sagital light beam. The slit lamp light must be placed directly in front of the eye which is to be examined, and the patient must fixate the light slit (i.e. a perpendicular light beam onto the cornea) and maintain gaze at a horizontal level. A vertical aperture on an anterior flange on the ACD measurer keeps the angle at 40 degrees and furthermore ensures that the examiner uses his right eye only. A narrow light beam passing through the anterior chamber can now be estimated monocularly (right eye). The section of light must be in the vertical-axial plane (i.e. edge of the pupil at 6 and 12 o’clock), and the section must be divided horizontally at 3 and 9 o’clock position. By moving the measuring arch to the left, the image in the single ocular is seen to divide; this is gradually increased until the optical section of the anterior lens capsule is aligned with the optical section of the corneal endothelium in the lower half (fig. 4). The best way to achieve this position is to use the next lowest magnification on the Haag-Streit slit lamp. This procedure directly determines the “internal ACD value” (excluding corneal thickness). We prefer this efficient and simple

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14


methodology instead of using the “external ACD value” (including cornea thickness), measuring from the anterior surface of the lens to the corneal surface. When using this last method, it is subsequently necessary to measure the corneal thickness with a similar measuring device (pachymeter I), and subtract this value from the “external ACD value” in order to calculate the accurate internal value. Recently it was documented that the directly measured “internal ACD value” using the pachymeter II alone was about 6% too high compared to the real ACD value measured by the more complicated “external” ACD method using pachymeter I + II46. As an example: An “internal” value of

Fig. 3. Axial chamber depth (ACD) measurement by means of optical pachymetry. Photo: The Glaucoma Clinic, Copenhagen University Hospital.

2.0 mm should then be reduced with 0.12 mm and an “internal” value of 2.5 mm with 0.15 mm. Ultrasonic or laser based chamber depth measurement ACD measurement may also be carried out using the ultrasonic Ascanning equipment normally used for cataract surgery biometry. It should, however, be stressed that an ultrasonic measurement determines the external value (including cornea). The “internal value” may then be found by subtracting the average cornea thickness of 0.5 mm, remembering that only one decimal is used with ACD measurement by the optical method. Therefore, it is impor-

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tant to specify whether the given measurement either includes or excludes the corneal thickness. When using ultrasonic determination, the ultrasonic head must be in contact with cornea, which may lead to corneal indentation with the risk of underestimating the chamber depth. This may be avoided by using the new laser-based non-contact biometrical technique, precisely as with optical pachymetry. Thus, these two methods are the most precise. It should, however, be noted that the laser-based biometry also measures the “external

Fig. 4. Methodology with optical pachymetry

ACD”, and that the corneal thickness must be subtracted, just as is the case with the ultrasonic method. Laser scanning pachymetry (Visante OCT system) This very new, versatile system provides high-resolution, noncontact optical coherence tomography, customized for the anterior chamber37. As the Visante OCT, apart from performing pachymetry, has also been designed to image and evaluate anterior chamber angles, this new unit might possess the necessary qualities for being one of the most essential tools in the diagnosis and clas-

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sification of PAC44. It is a disadvantage that the ciliary body is not visualized. Sources of error The average value of the normal axial chamber depth changes throughout life due to the growth of the lens. The axial chamber depth varies from approx. 3.2 mm (internal measurement) at puberty to 3 mm at the age of 40 and finally 2.7 mm at the age of 70. This pronounced age difference means that the importance of the ACD parameter in respect of a possible pupil-block conditioned risk of PAC is not as reliable among the 40-50-years old as it is among the elderly population when using the mentioned limit values. Therefore, it is important to stress that the required pathoanatomical PAC classification – as the condition is found among the younger population – is to a great extent dependent on an adequate gonioscopy. Apart from this, the biological ACD variation is marked and reaches ± 0.35 mm (corresponding to ± SD), increasing at a high age. On average, the values among women are 0.15 mm lower than those of men. If the mentioned limit values (2.0 and 2.5 mm) are found when examining a patient, the importance of these values as classification criteria should be subject to reservation, and it must be stressed that the final classification, especially in situations such as these, must, first and foremost, be determined by gonioscopy. Finally, ethnic variation is significant with low values among Inuits and East Asian people. In the case of cataract, the ACD value will in some cases decrease and in others increase.

GONIOSCOPY Introduction Gonioscopy should be carried out on a routine basis at the slightest suspicion of a glaucoma diagnosis. This examination is vital for the proper diagnosis and classification of glaucoma and hence for the specific treatment of the condition. Unfortunately, gonioscopy is riddled with problems when compared to other forms of glaucoma examinations as there are numerous

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possibilities for methodology errors connected to the gonioscopy procedure itself. Furthermore, interpretation of the gonioscopic view is difficult owing to the extensive biological variation of the normal anatomy of the chamber angle. Gonioscopy is very much an acquired art, and optimal utilisation of the procedure requires considerable personal experience. However, awareness of the sources of error and of the proper interpretation of the findings will result in a shorter learning phase. With this in mind, the following section therefore contains a thorough review of gonioscopy, including guidelines based on personal clinical experience over a considerable period of time. The aim is not only to provide an adequate, objective foundation for specific PAC treatment (ref: Introduction), but also to demonstrate a simple and purely practical standard procedure. The gonioscopy methodology described in this book (fig. 11) has, through decades of use by the authors, been proven both effective and reliable. Gonioscopy requires the use of goniolenses due to the fact that it is not possible to visualise the chamber angle directly through cornea at an angle as the light beam radiating from the chamber angle will be totally internally reflected. Furthermore, observation of Schlemm’s canal via the slit lamp is obstructed by the superficial scleral lip which covers the chamber angle (ref: Limbal chamber depth measurement (LCD), Sources of error). Goniolenses and their uses Gonioscopy requires the use of two different types of lenses for indirect gonioscopy of the individual eye; first a lens for a quick routine check – as well as an indentation gonioscopy (Posner’s) – then a more stable lens (Goldmann’s) for a detailed assessment without any real possibilities for indentation (fig. 5). It is particularly important to observe this requirement if the examiner is inexperienced. Also, optimum benefit from gonioscopy is dependent on good patient co-operation, which is only obtained through a thorough explanation of the procedure to the patient and a gentle technique without undue movements of the gonioscopy lens.

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Posner’s 4-mirror indentation lens There are several modifications of the Zeiss 4-mirror lens, however we recommend the Posner model (Zeiss lens with an angulated handle), which is the one used by the authors. The corneal contact area of the lens has a diameter of only 8 mm (fig. 5a). This is considerably less than the normal adult cornea (average diameter 11.5 mm) and provides a good basis for corneal indentation.

a

b

Fig. 5. Contact lenses for gonioscopy. a: The Goldmann lens on the left, the Posner lens on the right. b: Technique for gentle application of the Posner lens. Photo: P. Kock Jensen and Lars Solander, the Glaucoma Clinic, Copenhagen University Hospital

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At the same time, the smaller lens size makes it is easier to place the lens on the cornea. The gentlest way of placing the lens on the cornea is, following local anaesthesia, to catch the upper eyelid while the patient looks up with both eyes open and then place the lens centrally on the cornea while the patient looks straight ahead with both eyes open. The lower eyelid is fixed with the fingers holding the lens itself (fig. 5b). When examining the right eye of the patient, the Posner lens is held in the left hand, and the right hand is used for the left eye. The examiner should observe the eye through the slit lamp while placing the Posner lens on the eye. The contact area of the lens has a radius of curvature of 7.85 mm, i.e. the same radius of curvature as the surface of the cornea (average 7.8 mm). This has the advantage that a contact medium such as methylcellulose is unnecessary, as the tear film is quite adequate. In this way, it is easy to change between the two eyes for the necessary comparison. If the lens is not held completely parallel with the surface of cornea, air bubbles will enter between the lens and cornea in part of the contact area. The easiest way of eliminating any air is by rotating the round handle of the lens carefully between the thumb and index finger until the contact area is freed from air. Use of methylcellulose cannot be recommended as a contact medium will only make the examination more unstable. Posner gonioscopy should therefore be performed before Goldmann gonioscopy using methylcellulose! The lens may be held in two ways (fig. 6a-b). When initially assessing the lower and upper chamber angle area (see below), the lens handle is held directly (fig. 6a) since this will create an upper and lower horizontally positioned mirror. If a subsequent examination of nasal and temporal angle areas is desired, the examiner should hold the lens with his fingers indirectly around the horizontally positioned handle (fig. 6b), thus placing all the mirrors at an angle. By positioning the lens in this way, it is possible to have an overview of almost the entire angle without having to rotate the slit lamp light (see below). The rest of the angle may be seen by turning the lens a mere 11 degrees.

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a

b

Fig. 6. The application of the Posner lens with different grips. a: Holding the lens handle directly for assessment of the upper/lower angle. b: Holding the lens handle indirectly for assessment of the nasal/temporal angle. Photo: Lars Solander, the Glaucoma Clinic, Copenhagen University Hospital.

The examination with the Posner lens consists of two steps: 1. Examination in the primary position without indentation with regard to open or narrow angle Assessment of upper/lower angle area is carried out holding the lens as shown in fig. 6a and mounting the lens in an axial position on the cornea while the patient looks straight ahead. The lens is

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impressed only slightly until no air remains (7a). A certain amount of experience is required in order to achieve a stable position for the examination.

a

b

Fig. 7. Posner lens application. a: Without indentation. b: With indentation.

In order to ease the use of the technique, we can recommend the following (fig. 8). Adjust the chin rest on the slit lamp so that you may rest your elbow on the slit lamp table. If your arm is too short, you may use an “elbow block”. Hold the handle of the lens close to the edge of the lens so that you may rest your hand on the chin of the patient. This will give a better control of the lens as the lens moves freely on the cornea. Make sure that the lens is placed in an axial position by then looking directly at the patient instead of through the slit lamp and check that the patient has both eyes open and is looking straight ahead. This is the primary examination position. It is important to note that the patient will often close the other eye spontaneously, resulting in an unstable examination situation.

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Fig. 8. Position of hand and arm when working with Posner lens gonioscopy (the elbow is placed on the slit lamp table!). Photo: Lars Solander, the Glaucoma Clinic, Copenhagen University Hospital.

2. Examination in the primary position with indentation with regard to peripheral anterior synechiae (PAS-closed angle) The next step is the axial indentation in the primary position (fig. 7b) with simultaneous observation of the chamber angle anatomy, especially with regard to any peripheral anterior synechiae (PAS) as well as having iris contour and mobility in mind. If the space is very narrow the visualisation of the angle anatomy does, however, require the patient to look towards the angular mirror used in order to observe the peripheral side of the iris convexity instead of maintaining the primary position. But this procedure is difficult due to the instability of the lens. Indentation on a very soft eye may easily lead to indistinct folds of MD when the indentation is excessive, which is yet another reason why the Posner lens should be used before the Goldmann lens. When tension rises above 30 mmHg, indentation becomes increasingly difficult, mainly due to

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pain reaction. Adequate indentation gonioscopy is therefore very difficult to perform with untreated acute PAC at high pressures. However, the possibility of carrying out indentation is improved if the patient is well informed beforehand. The lens is therefore ideal for routine gonioscopy with the aim of initially assessing the situation in both eyes. It is essential not only in connection with indentation gonioscopy with respect to PAS (fig. 7b) but also in the assessment of iris contour and mobility (ref: Normal anatomy of the chamber angle). The lens is however, especially in the hands of the inexperienced, too unstable for evaluation of small chamber details under high power magnification (e.g. occludable angle? due to PAC). It is therefore recommended to combine its use with the Goldmann gonioscopy lens, especially in the learning phase. It is important to note that apart from the mentioned advantages, the Posner lens is absolutely essential for carrying out adequate examination of very narrow angles. In such situations, it is only possible to visualise peripheral synechiae by using the Posner lens. This fact has aroused increasing international support during the last decade, and it must be strongly advised that one should use the lens on a routine basis Goldmann’s gonioscopy lens There are two types of Goldmann lenses: The 1-mirror and the more efficient 2-mirror model. The contact surface on the lens has a diameter of 15 mm with a larger curvature than that of the cornea (fig. 5a). This means that the lens in the primary position rests mainly on the sclera and requires the use of a contact medium in order to avoid air seeping into the space between the lens and the cornea. Therefore, the lens is not suitable for corneal indentation, but it is more stable once it has been placed on the eye, which means that it is not necessary to use an elbow rest and the left hand for examination of the patient’s right eye as is the case with the Posner lens. A Goldmann lens is easier to use with higher magnification when observation of small details is required and where corneal indentation is not needed (e.g. narrow-occludable angle?).

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Because the Goldmann lens is larger than the Posner lens, it is more difficult to place it on the eye and more irritating for the patient than the smaller Posner lens, especially if the patient has a tendency to squeeze the eyelids together. The easiest way to place the lens on the eye is to observe the eye directly and not through the slit lamp. Examination with the Goldmann lens is carried out in two stages: 1. Examination in the primary position for open or narrow angle. 2. Examination while the patient looks into the angular mirror with regard to an occludable or appositional-closed angle. When small peripheral anterior synechiae (PAS) are diagnosed following indentation gonioscopy with the Posner lens, it is possible to verify their presence when the patient looks directly into the angular Goldmann mirror. However, because of its size and the use of a contact medium, the Goldmann lens will irritate the patient more than the Posner lens, and if only the Goldmann lens is used, the examiner will most likely be tempted only to examine one eye, also in order to avoid bilateral blurring of vision, which follows the use of methylcellulose. For adequate examination of both nasal and temporal angle sectors it is furthermore necessary to rotate the slit lamp light away from the usual vertical position to a more horizontal level when using the Goldmann lens. As mentioned above, this is not necessary with the Posner lens. In this connection, it should be stressed that gonioscopy should always be carried out bilaterally in order to avoid misinterpretation due to the considerable inter-individual variation of the normal anatomy. The reason why this important possibility exists is to be found in the fact that the normal chamber angle anatomy is almost always identical in the two eyes. In case of PAC suspicion the unaffected or less pathologic eye should also be used as a control eye, because the PAC predisposition is bilateral (ref: ACD measurement). The initial examination with the Posner lens makes it possible to repeat “back and forth” assessments between the two eyes without excessive irritation and usually means that

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a subsequent Goldmann gonioscopy examination need only be performed on the one eye. This combined use of the two lenses is recommended, especially in the learning phase. Goldmann’s 3-mirror lens is not recommended for gonioscopy for several reasons. Firstly, because the contact surface of the lens has a diameter of 18 mm, which makes it more difficult for the patient to look into the angular mirror. Secondly, the degree of slope on the 3-mirror lens gonioscopy mirror is slightly different from that of the Goldmann lens, which means that the occludability of the angle will be assessed differently. However, we recommend use of Goldmann’s 3-mirror lens for inducing blood flow into Schlemm’s canal with the intent of identifying the canal, because the large lens diameter makes it possible to compress the aqueous veins (ref: Normal anatomy of the chamber angle, The uveal meshwork (iris processes)). Gonioscopy methods with PAC The necessary basis for adequate gonioscopy methodology requires not only a clear and practically applicable chamber angle classification based on carefully defined definitions but also the application of standardised examination techniques. Chamber angle: Classification and definitions 1. Open or primary narrow angle The size of the chamber angle is the most important and often most difficult gonioscopy assessment that has to be made. The reason for this is partly the previously mentioned considerable inter-individual normal variation of the angle structures and partly the normal intra-individual variation in the degree of opening within the different angle sectors. Under normal circumstances the angle is more open in the lower sector than in the upper sector. This is specially the case at 6 o’clock (the physiological “angle coloboma”). In eyes with narrow angles the degree of narrowness is also more pronounced in the upper sector than in the lower which again is narrower than the temporal and nasal sectors38. Furthermore, the iris root usually has an undulating configuration, and the final conclusion as to

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the degree of narrowness has to be based on a judgement of the upper and lower halves of the angle separately. The problem is further complicated by the fact that different angle classification methods are recommended. Scheie4 uses the identification of the individual angle structures as a basis for his assessment, and if the pigmented trabecular meshwork (Schlemm’s canal) is not visible, the angle is described as narrow. Schaffer5, on the other hand, uses the geometric angle between the trabecular meshwork and the anterior surface of the iris for classification, and an angle of 10 degrees is described as a narrow angle. Spaeth’s methodology6 is a somewhat complicated development of Schaffer’s methodology. Since the chamber angle may not be directly measured via the slit lamp, the geometric angle specification will hint an unrealistic objectivity. Therefore, throughout the last decades, we have used a classification system based on a simplification of Scheie’s identification technique concerning an open or narrow angle. However, the uncertainty of this principle is that it is necessary to carefully observe the standardised examination techniques in order to avoid misinterpretations. For instance, if one is unaware that the contact lens has been placed at an angle and not on the optical axis in the centre of cornea, the pigmented trabecular meshwork may be visualised, and the angle may then incorrectly be perceived as being open. Furthermore, the above situation will often result in lens indentation and thereby affect the degree of opening. In order to avoid these problems, a standardised examination technique is aimed at as described in the previous section: Examination in the primary position for open or narrow angle (Posner and Goldmann lens). Based on the above principles: An open angle is defined as an angle in which all of the pigmented trabecular meshwork or Schlemm’s canal (in case of unpigmented trabecular meshwork) can be identified over the entire circumference when carrying out the examination in the primary position without indentation. (see fig. 9). A primary narrow angle may be defined as an angle in which the pigmented trabecular meshwork or Schlemm’s canal, using the same examination techniques, by and large

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Fig. 9. Varying degrees of open/narrow angle: The two drawings on the left: Pigmented trabecular meshwork is visible, implying open angle. The two drawings on the right: Pigmented trabecular meshwork is not visible, implying narrow angle. The drawing in the middle: Pigmented trabecular meshwork is partly visible, implying, for instance suspect PAC, as appears in the lower angle sector. a: Sampaolesis’ line. b: Pigmented trabecular meshwork. c: Scleral spur. d: Ciliary band. e: Iris knee.

cannot be identified either in the upper half or in the lower half of the chamber angle (see fig. 9). The use of the Posner lens for diagnosing narrow angle demands a certain amount of experience with the lens, which is why beginners are advised to verify the diagnosis by subsequently performing gonioscopy with a Goldmann lens. This, however, does not conclude the examination. The primary narrow angle is now either occludable or closed, and the closed angle is either closed due to iris/cornea apposition (appositionalclosed”) or due to synechiae (“PAS-closed”) as shown in fig. 10. Therefore, it should be noted that the term narrow angle is not in itself satisfactory, but always demands a further adjective for adequate objective description of the existing PAC possibilities. 2. Narrow-occludable angle or narrow appositional-closed angle These classification terms are used when the initial Posner gonioscopy reveals a narrow angle without PAS. Using the Posner lens, this is only a diagnosis of exclusion since it is only really possible to carry out this classification for certain with a subsequent Goldmann gonioscopy without any indentation. When the patient, with this more stable examination, looks into the angular mirror (fig. 11) and the pigmented trabecular meshwork is

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open angle occludable

Gonioscopy

appositional

narrow angle closed

PAS

Fig. 10. Terminology with gonioscopy examination.

visible, a narrow-occludable angle is present, whereas a meshwork that is not visible implies an appositional-closed angle. 3. Narrow synechiae-closed angle As mentioned previously, the diagnosis of PAS is best undertaken using indentation gonioscopy with the Posner lens. The identification of trabecular meshwork is the requirement for a reliable PAS diagnosis since PAS formation is often adherent to the meshwork. The identification requires an evaluation of the amount of pigment in the meshwork of the individual patient, which is best gained in the lower part of the angle at around 6 o’clock (“angle coloboma”). This particular area is hardly ever closed with synechiae (ref: The normal anatomy of the chamber angle, the corneoscleral trabecular meshwork). Following this, it is possible to verify synechiae contact to trabecular meshwork. Moreover, in order to verify PAS, careful observation of the transition zones between PAS free angle areas and synechiae areas is to be recommended since trabecular meshwork contact is best observed here. 4. Abnormal iris contour and iris mobility When diagnosing a narrow angle, it is important to be aware of the fact that the gonioscopy examination is not complete until the iris contour and mobility have been assessed since this assessment is necessary for the differential diagnosis between pupil block and plateau conditioned PAC36 (ref: Chamber angle – normal anatomy). The examination can only be carried out by using the Posner lens.

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It should be stressed that the above mentioned gonioscopic classification (1-2-3-4) is of vital importance for the specific PAC treatment (ref: Introduction). Standardised PAC gonioscopy methodology As stated in the previous section concerning chamber angle classification, gonioscopy requires standardised examination techniques in order to avoid misinterpretations. Apart from the above-mentioned guidelines, the following should be noted: – The examination should always be carried out under dimmed illumination and using as small a slit lamp light as possible, i.e. the aperture of light should be narrow and set low. – If a strong light is shone through the pupil the miosis obtained may open the angle to such a degree that one might misinterpret the angle as being open. – For the same reason and especially if threatening (imminent) PAC is suspected, pilocarpine should not be used for at least six hours before gonioscopy! – Always start the gonioscopy procedure by examining the lower sector of the angle around 6 o’clock (the physiological “angle coloboma”). The first task is always to identify the pigmented trabecular meshwork (Schlemm’s canal) and, if possible, also the scleral spur and ciliary band. Since the angle is always most open around 6 o’clock, it is nearly almost always possible to see the pigmented trabecular meshwork in the “angle coloboma”, even if synechiae have spread to the remainder of the angle. When the degree of trabecular meshwork pigmentation has been estimated as well as the appearance of other identifiable angle structures at 6 o’clock there will be a basis for identifying the angle structures in the rest of the circumference. We therefore recommend: Start with the lower sector of the angle and work upwards to the point at which the synechiae start. The examination of the sides should be left to last since this is where the examination is most difficult. – Always start by comparing the angle anatomy in the two eyes, i.e. start with the Posner 4-mirror lens as this lens may be easily moved back and forth between the two eyes.

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Start the examination with the Posner lens 4-mirror lens 1. Examination in the primary position without active indentation The primary position is the position in which the patient looks straight ahead (make sure that the patient keeps the other eye open!!) and the lens is placed centrally on cornea in an axial position with as little pressure as possible; enough, however, to avoid air entering between the lens and cornea. With respect to “user tips”, ref: Goniolenses and their uses. In order to ensure that the examination is carried out in the primary position, it is necessary from time to time to look directly at the patient instead of through the slit lamp. Drawing 1A, fig. 11 shows that pigmented trabecular meshwork may be identified by examining the patient in the primary position, both in the upper and lower sectors of the angle (objectively), and according to the definition of an open chamber angle given earlier (ref: Chamber angle: Classification and definitions) the final conclusion is that here we have an open angle. Drawing 1B, fig. 11 shows, according to previous definition, that it is a narrow angle as the pigmented trabecular meshwork cannot be identified on examination in the primary position due to a prominent convex iris contour. It will be necessary to continue the gonioscopy in this situation. 2. Drawing 2, fig. 11 also shows an examination in the primary position with the Posner lens, only now with indentation. From the drawing it appears that the pigmented trabecular meshwork is not visible in the upper sector due to PAS, but now visible in the lower sector and without PAS, i.e. the angle is PAS-closed in the upper sector and presumably occludable or appositional closed in the lower However, as mentioned earlier, the Posner lens is often too unstable for determining whether the angle is occludable or appositional closed as such a determination will require stable inspection under high magnification. Therefore, it is necessary to use the Goldmann lens for a subsequent examination of the lower sector, especially if the examiner is inexperienced with using the Posner lens. If the acute angle-closure has not been treated and the IOP is high (> 30 mmHg), it is difficult to adequately indent with the Posner

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Standardised PAC gonioscopy – methodology Patient

Lens

Objectivity

Conclusion

1. Examination in the primary position without indentation PATIENT A

Posner

Pigmented trabecular meshwork visible in the upper and lower sectors.

Open angle, not occludable.

PATIENT B

Posner

Pigmented trabecular meshwork not visible in the upper and lower sectors. Convex iris contour.

Narrow angle. Req. indentation gonioscopy.

2. Examination in the primary position with indentation PATIENT B

Posner

Pigmented trabecular meshwork not visible in the upper sector (due to PAS), but visible in the lower (without PAS). Mobile iris.

Synechiae-closed in the upper sector. Occludable or appositional closed in the lower sector due to pupil block (convex mobile iris). Req. Goldmann gonioscopy of the lower sector

3. Examination in the primary position PATIENT B

Pigmented trabecular meshwork not visible in the lower sector.

Narrow angle in the lower sector. Req. Examination with the patient looking into the angular mirror.

Goldmann

4. Examination with the patient looking into the angular mirror PATIENT B

Pigmented trabecular meshwork visible in the lower sector.

Goldmann

Occludable angle in the lower sector. Final conclusion: Chronic PAC with pupil block, with PAS-closed angle in the upper sector and occludable angle in the lower.

Fig. 11. Standardised PAC gonioscopy methodology. Diagram: Svend V. Kessing. Drawings: Jørgen Kampp, Tellus Publishing, Denmark.

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lens, not least due to the patient’s reaction to the pain. Furthermore, the cornea is usually oedamatous, which means that, at best, the examiner is able to make the diagnosis of closed angle due to PAC, but is not able to determine if the angle is appositional closed or PAS-closed. In this situation, it is therefore necessary to instigate acute medical treatment in order to lower the pressure (ref: Treatment of acute PAC) and to apply local treatment with 50% glucose eye drops in order to clear the cornea before attempting a further Posner indentation. In the event of suspicion of appositional angle closure with a patient who does not react to the pain, a good tip for lowering the pressure is to perform an intensified, but gentle cornea indentation with the detached plastic cone from the Goldmann applanation (ref: Treatment of acute PAC). Continuation with Goldmann’s gonioscopy lens 3. As shown in drawing 3, fig. 11, the examination of the lower sector is initially performed using the Goldmann lens in the primary position with a high slit lamp enlargement, and if the trabecular meshwork is not visible, it can be concluded that there is a narrow angle in the lower sector. 4. The next step is the examination with the Goldmann lens with the patient looking directly into the angular mirror of the lens as shown in drawing 4, fig. 11. If Pigmented trabecular meshwork is visible when using this procedure, the examiner may conclude that the angle is occludable in the lower sector. We recommend this procedure rather than having the examiner move the lens lower down on the eye and thereby risking an indentation with the lower edge of the lens, which may induce pain. This will make it difficult to obtain an optimal result from the gonioscopy. Gonioscopy findings Normal anatomy of the chamber angle The normal anatomy of the chamber angle shows a considerable inter-individual variation, but little intra- individual difference

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between the two eyes. This is why one eye may normally be used as a control eye with respect to the pathoanatomy in the other eye. However, this is only possible if the examiner has a thorough knowledge of normal variations of the angle anatomy. Seven different angle structures should be assessed in connection with gonioscopy (fig. 12): 1. Iris contour and iris mobility 2. The uveal meshwork (iris processes) 3. The ciliary band 4. The scleral spur 5. The corneoscleral trabecular meshwork 6. Schwalbe’s line 7. Normal blood vessels in the angle

Fig. 12. The four structures of the normal chamber angle.

1. Iris contour and iris mobility The best way to assess the iris contour (fig. 13) is to use the Posner lens (ref: Goniolenses and their uses) since this lens will show the entire radial iris contour from pupil edge to periphery, whereas the Goldmann lens only shows the peripheral part of the iris. In the normal emmetropic adult eye, the iris is slightly anteriorly convex due to a slight physiological pupil block, which makes the pressure in posterior chamber slightly higher than in anterior chamber. In the case of hypermetropia, the iris contour is typically more anteriorly convex, while the iris contour of myopic eyes is either flat or concave (fig. 13). These conditions are accentuated with eye pathology. Hypermetropic PAC eyes with pupil block as well as eyes with secondary angle-closure (SAC) due to axial lens ad-

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vancement will have an extreme iris convexity (see below). In the case of plateau conditioned PAC, on the other hand, the iris is abnormally flat, whereas the myopic pigment glaucoma eye often has an extreme iris concavity.

Fig. 13. Iris contours.

The iris mobility is examined by applying indentation with the Posner lens in the primary position (fig. 7b). Mobility assessment is based on two factors; partly on the change of the entire radial iris contour and partly on the change of the degree of narrowness in the chamber angle. The latter may be quantified by the degree of visibility of the main angle structures. (fig. 12). Among healthy people, the iris is so mobile that with a slight indentation the iris can concave from the pupil border up to the iris root. At the same time, this will open the angle and make the tip of the angle visible, enabling identification of all of the structures of the angle, including the ciliary band. The latter is due to the fact that the iris root or “the iris knee” (the last roll of iris) can almost be levelled out completely among healthy people. In connection with glaucoma pathology, the mobility may either be considerably increased (PAC with pupil block and pigment glaucoma) or extremely decreased (PAC with plateau iris and SAC due to axial lens advancement). As will be described in greater detail later, the two main groups of PAC have quite a different anatomical pathogenesis: Abnormal pupil block or plateau iris. The assessment of iris mobility remains one of the most important methods available for separating these two important clinical entities . In connection with abnormal pupil block, the narrow angle is conditioned by aqueous accumulation in the posterior chamber resulting in an anteriorly convex iris, whereas the narrow angle 36

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in the case of plateau iris is caused by an abnormal anterior positioning of the ciliary body7 and thereby the iris root (“the iris knee”), which will then be levelled with the trabecular meshwork (see the UBM pictures: fig. 14 and fig. 23). This pathoanatomy is also the reason why the iris contour is flat.

Pupillary block

Corneal indentation

Control

Plateau iris

Fig. 14. UBM iris contour and mobility before and after indentation. Top: Pupil block conditioned PAC. Bottom: Plateau iris conditioned PAC. Photo: P. Kock Jensen and Svend V. Kessing, the Glaucoma Clinic, Copenhagen University Hospital.

The different forms of pathogenesis result in two different types of iris mobility: In the case of pupil block, on indentation gonioscopy the iris becomes anteriorly concave over its entire radius (fig. 14, top). In connection with early cases without synechiae and increrased IOP, even the most peripheral angle anatomy, including the ciliary band, will usually be visualised. In the case of plateau iris, on the other hand, indentation will only produce a small intermediary located iris concavity, and “the iris knee” will barely alter (fig. 14, bottom). In this situation, the identification possibilities of the angle structures change very little, maybe with a slightly better visualisation of the trabecular meshwork while the ciliary band remains invisible. This is due to the fact that the ciliary body functions as a “chock” for contour changes of the peripheral iris8 (fig. 14 and 23).

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Consequently, assessment of iris mobility represents an important part of gonioscopy with special differential diagnostic consequences within the area of PAC. 2. The uveal meshwork (iris processes) The uveal meshwork is probably the angle structure that shows the highest degree of normal variation. This may well result in a misinterpretation, and a normal anatomy be considered as pathological with the consequent risk of providing improper therapy. Therefore, it is particularly important to be familiar with the uveal meshwork. During the formation of the anterior chamber in the embryonic period, the chamber is filled with loose fibrous tissue, which is covered by a homogeneous layer of glittering endothelium cells towards the chamber. The remainder of this tissue comprises the uveal meshwork. In newborn babies the uveal meshwork still has a colourless, homogeneous, pellucid structure, extending from the root of iris across the angle to the anterior part of the underlying corneoscleral trabecular meshwork. Visualisation is difficult and requires high enlargement. After this, an increasing regression of the tissue with fenestration of the endothelial surface and the fibril development is usually seen. Among adults the uveal meshwork is thus more or less pigmented, depending on the colour of the eye, and always has a lace-like porous structure stretching from the root of iris to the scleral spur. In some cases, coarser fibrillary structures are seen, the so-called iris processes (fig. 12), which are situated in front of the underlying more flattened fenestrated uveal meshwork. Sometimes, the iris processes stretch right up to the corneoscleral trabecular meshwork. The uveal meshwork is usually most well-developed nasally in the angle and least-developed at 6 o’clock (the physiological “angle coloboma”). When regression of the endothelium-covered uveal meshwork does not occur, goniodysgenesis will arise, which is most likely the reason for congenital and infantile glaucoma and possibly also for juvenile glaucoma. At times, the uveal meshwork containing the many iris processes will be misinterpreted as representing goniosynechiae, and the

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examiner may misdiagnose the patient as having a chronic angleclosure and consequently may even perform a YAG iridotomy!! (See 2nd case report). This situation is especially seen among younger people with brown eyes where the corneoscleral trabecular meshwork still remains unpigmented, whereas the uveal meshwork and the iris processes are heavily pigmented and therefore especially clear. The examiner does not acknowledge the actual location of Schlemm’s canal in front of the scleral spur, but instead regards the slightly pigmented ciliary band (fig. 9) as representing the corneoscleral pigmented trabecular meshwork. The risk of making this misinterpretation is especially high among patients with juvenile glaucoma. In order to avoid this misinterpretation, we recommend the following: Using the Goldmann 3-mirror lens in the primary position, carry out compression until the eye is soft. Then decompress while applying a slight scleral pressure with the edge of the lens in the opposite direction of the angular mirror; in most cases, this will produce a retrograde filling of blood into the observed part of Schlemm’s canal (fig. 15a). The large contact surface of the 3-mirror lens (18 mm) is usually necessary for adequate scleral compression of the aqueous veins and thereby retrograde filling of blood into the canal. This procedure helps identify the position of the canal and the true facts of the case. In order to avoid misinterpretation, it is important to be aware of the gracile lace-like structure of the uveal meshwork and the iris processes as opposed to the more solid genuine goniosynechiae (fig. 15b). 3. The ciliary band The ciliary band is formed by the longitudinal fibres of the ciliary muscle on their way to the scleral spur. Gonioscopically, the ciliary band stretches from the root of iris to the scleral spur (fig. 9). As mentioned in point 2 above, the ciliary band is partly hidden under the uveal meshwork, especially among people with brown eyes (fig. 12), but it is always seen in the “the angle coloboma” at 6 o’clock. Usually, the colour is slightly grey – a little greyer than the unpigmented corneoscleral trabecular meshwork. However, among dark-eyed people the colour is slightly pigmented and may therefore easily be confused with the pigmented trabecular meshwork.

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The width of the ciliary band depends on the iris insertion on ciliary body and varies considerably from person to person. In the

a

b

Fig. 15. Differential diagnosis between iris processes and PAS. a: Visualisation of the position of trabecular meshwork with blood filling of Schlemm’s canal. b: Left: Lace-like iris processes. Right: Solid PAS up to the scleral spur.

case of myopia, the ciliary band is wide, but in connection with plateau conditioned PAC it is mostly invisible where the iris is inserted right behind the scleral spur (see below). 4. The scleral spur The scleral spur forms the posterior edge of the corneoscleral trabecular meshwork directly in front of the ciliary band (fig. 12),

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and is, as such, often covered by the uveal meshwork except in the lower part in “the angle coloboma”. The scleral spur has the same white colour as the unpigmented trabecular meshwork, but is usually easily seen in connection with averagely pronounced pigmentation of the meshwork since it will then lie in between two darker and wider lines (fig. 9). When the scleral spur has been identified at 6 o’clock, it can usually be found under the uveal meshwork in the rest of the angle. 5. The corneoscleral trabecular meshwork The corneoscleral trabecular meshwork stretches from the scleral spur to Schwalbe’s line (fig. 12), and Schlemm’s canal lies deeper in relation to the middle and posterior 1/3 of the meshwork. Among adults, this filtering part of the meshwork is usually slightly pigmented and as such is easy to identify since the degree of pigmentation is always least temporally around the horizontal line and largest nasally in the lower quadrant, where the uveal meshwork is also most pronounced. Among children and younger people the trabecular meshwork is unpigmented. The unpigmented meshwork may be identified via its typically greyish, slightly granulated pellucid surface; this becomes slightly clearer when applying indentation with the Posner lens. If the trabecular meshwork is difficult to identify, its position between the scleral spur and Schwalbe’s line can be used as a guideline as these two structures are easier to locate, especially in the “angle coloboma” at 6 o’clock (see below). Finally, as mentioned earlier, a positive identification of Schlemm’s canal is possible if the canal is filled with blood by using the Goldmann 3-mirror lens (fig. 15a). 6. Schwalbe’s line Schwalbe’s line is formed by the peripheral edge of Descemet´s membrane with direct contact to the anterior part of the corneoscleral trabecular meshwork (fig. 12). The line may be more or less prominent, but in most eyes it is usually most easily visualised in the lower direction, mainly because it is considerably more pigmented at around 6 o’clock (Sampaolesis’ line, fig. 9). This makes it easier to identify the right location of the corneoscleral trabecular meshwork in this sector, but may also give rise to misinterpretation. On examination with the Goldmann lens, the

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pigmented line in the lower angle sector shown in fig. 16a was thought to be the pigmented trabecular meshwork, and the angle was therefore considered as being open, not occludable. However, later examinations with the Goldmann lens with the patient looking into the mirror showed that the pigmented trabecular meshwork was situated further back, partly covered by goniosynechia (fig. 16b). This was therefore an eye with chronic angle-closure and with a most pronounced Sampaolesis’ line. Sometimes, Schwalbe’s line is very thickened and prominent and may even be seen both on direct slit lamp examination and with gonioscopy. This condition is called posterior embryotoxon and is, as a solitary finding, an insignificant normal variation of Schwalbe’s line. If there are further developmental defects in the chamber angle (Axenfeld’s and Rieger’s syndrome), marked iris attachments will be connected to the embryotoxon formation with a subsequent risk of glaucoma. 7. Normal blood vessels in the angle Normal blood vessels in the chamber angle are seen with considerable inter-individual variation; however in spite of this, they do have certain characteristics, which do make it possible to distinguish them from neovascularisation (angle rubeosis). Normally, the main ciliary arterial circle runs parallel to the limbus in the anterior part of the ciliary body and is invisible on gonioscopy. Sometimes, part of the main ciliary arterial circle is visible in a sector of the ciliary band where its curved course, with only a part of each loop being visible, resembles a sea serpent. The radial iris vessels run from the arterial circle and through to the iris root in the iris pigment layer and from there onwards into the iris stroma with a radially visible course towards the pupil covered by a thin layer of iris stroma and with only a few diagonal anastomoses. The veins from the pupil border also run in a straight radial line towards the iris root. Finally, in slightly pigmented eyes it is sometimes possible to see a radially situated artery deep within the ciliary band, presumably an anterior ciliary artery after the scleral passage on its way to the main ciliary arterial circle.

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a

b

Fig. 16. Differentiation between Sampaolesis’ line and the pigmented trabecular meshwork. a: Examination of the lower angle in the primary position with the Goldmann lens – visible pigmented trabecular meshwork? b: Examination of the same eye with the patient looking into the mirror in the Goldmann lens –pigmented trabecular meshwork and PAS + Sampaolesis’ line. Photo: Svend V. Kessing, the Glaucoma Clinic, Copenhagen University Hospital.

Glaucoma pathology in the chamber angle After a diagnosis of narrow angle, gonioscopic identification of peripheral anterior synechiae (PAS) is the most important observation, partly in order to verify the PAC diagnosis and partly as a way of correctly PAC staging of each individual case with regard to specific treatment. PAS develop insidiously from the most narrow, upper angle sector and downwards39.

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As mentioned under “Normal anatomy of the chamber angle” (2: The uveal meshwork (iris processes)), it may be difficult to distinguish between PAS and a physiologically pronounced uveal meshwork with iris processes (see fig. 15a-b). PAS with PAC are more solid when compared to the porous lace-like uveal meshwork, and furthermore they are clearly formed by the iris stroma. Most often the synechiae emanate from the deepest part of the angle and have a continuous adhesion to the angle wall, in some cases right up to Schwalbe’s line, though never centrally to it. However, in case of very small PAS they sometimes emanate from the trabecular meshwork. The duration of appositional angle-closure necessary to form PAS is not known, but is probably dependent on the degree of inflammation in the angle area, pressure- or only apposition-conditioned. The latter seems to be the most frequent as up to 2/3 of all cases of PAC develop asymptomatically as “creeping” angle closure17, 34, 35. In the case of suspect narrow angles, the PAC diagnosis may be verified by the occurrence of a single, but well-defined PAS in the upper narrowest sector of the angle. Based on a semi-quantitative estimate, the occurrence and spreading of PAS form the basis for the subclassification (staging) of PAC, opening up the possibilities for specific treatment. With a PAS involvement of < 50% of the angle circumference the remainder of the outflow function will normally be sufficient to maintain a normal IOP without treatment, whereas without medical treatment the eye pressure will permanently be increased when PAS comprises > 50% of the circumference. Finally, involvement of > 80-90% often signifies a manifest glaucoma with indication for maximum drug administration/fistulating operation (see flow chart for specific treatment of primary angle-closure, fig. 19). As is well known PAS are not pathognomic for PAC as they are found following uveitic inflammation, after a post-operative flattened anterior chamber, neovascular glaucoma, iridocorneal endothelium syndrome (ICE syndrome) and in congenital defects with development arrest (Axenfeld, Rieger). Whereas PAS are frequently seen after iris bombé, they are seldom seen following acute iritis and then presumably only in connection with a concurrent narrow angle. The development of synechiae is far more common in cyclitis with “fat” precipitates. As is clearly seen in

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the cyclitic trabeculitis (Boeck´s disease), the likely explanation is that the “fat” precipitates are mainly deposited on the trabecular meshwork in the lower part of the chamber as prominating pellucid “jelly-fish”; in extreme cases they are continuous with and in contact with the iris. When these precipitates become organised, large tent-shaped synechiae are formed in the lower area of the angle; therefore, apart from by the degree of the opening of the chamber angle, it is possible to distinguish them from PAS with PAC by their morphology and localisation. As in PAC, the synechiae are never central to Schwalbe’s line as opposed to neovascular glaucoma where the synechiae do sometimes extend centrally to Scwalbe’s line. This is also the case in the ICE-syndrome and with congenital defects. Neovasularisation in the anterior segment of the eye is, especially in the initial fase, limited to the chamber angle (angle rubeosis) and can therefore only be diagnosed by means of gonioscopy. In any condition where there is a risk of neovascularisation in the anterior segment, it is advisable to perform a gonioscopy. Angle rubeosis is seen secondary to two different groups of diseases: 1. Vascular retinopathies (central artery or vein occlusion, diabetes, carotid artery stenosis, possibly with normal pressure glaucoma, Eales disease). 2. Chronic inflammations (chronic iridocyclitis, chronic anterior uveitis, Fuchs’ heterochromic cyclitis). In both groups of diseases the new vessels arise from the main arterial circle in the ciliary body and from there run radially onto the anterior iris and the posterior cornea. The new iris vessels have an irregular, curved course on the surface of the iris as opposed to the normal iris vessels (ref: Normal blood vessels in the chamber angle). The new vessels on the posterior surface of the cornea appear on the ciliary band and from here run radially and superficially across the scleral spur up to the trabecular meshwork where the vessels branch out circumferentially in the filtrating part of the meshwork. The new vessels are accompanied by a transparent layer of fibrotic tissue, which occludes the meshwork and causes secondary glaucoma.

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In vascular retinopathies, the fibrovascular activity is considerably more pronounced than in inflammatory conditions. In the course of weeks the new vessels will, in these conditions, lead to the formation of broad solid PAS leading to further increase in pressure. The synechiae formation is caused by shrinkage of the accompanying fibrotic tissue along the new radial vessels. The concurrent shrinkage of the fibrovascular formation on the iris results in uveal ectropion of the pupil. It should therefore be emphasised that the angle rubeosis in inflammatory conditions does not usually cause PAS formation and is on the whole less harmful with thinner angle vessels. However, in heterochromic uveitis the thinner vessels show a tendency to bleed, both spontaneously and in connection with an operation. Abnormal chamber angle pigmentation localised only in the trabecular meshwork is seen among younger patients with pigment dispersion and among elderly patients with pseudoexfoliation. In both these cases, the temporal meshwork sector becomes just as pigmented as the remaining circumference, which is not found under normal conditions. In pseudoexfoliation, pigmentation as well as pseudoexfoliation material can be found on the trabecular meshwork in the lower angle sector in addition to the typical material on the pupilliary margin and the anterior surface of the lens. Coarser, diffuse pigmentation, most pronounced on Schwalbe’s line in the lower angle (Sampaolesi´s line), is seen following inflammatory conditions, for example after acute PAC. Diffuse pigmentation of the chamber angle in connection with other signs of previous acute PAC (“glaukomphlecken” and sector shaped grey iris atrophy, ref: acute/subacute PAC with pupil block) may thus have a differential diagnostic importance. Black, coarse pigmentation in the lower angle, possibly with some rounded pigmentation, is typical for previous hyphaema, often arising in connection with a contusion trauma. In the latter case, apart from this coarse angle pigmentation, other post-traumatic chamber angle changes can be found such as limbus-concentric clefts in the uveal meshwork, in the ciliary band (cyclodialysis) or in the corneoscleral trabecular meshwork (traumatic trabeculotomy). In connection with traumatic trabeculotomy, even a long time after the trauma, it is possible to cause bleeding into the

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chamber through the damaged trabecular meshwork (elimination of the meshwork’s unidirectional valve effect) by retrograde filling of blood into Schlemm’s canal (ref: Normal anatomy of the chamber angle:The uveal meshwork). A similar situation exists with a post-inflammatory meshwork lesion following an iritis. Moreover, especially after a contusion, a sector shaped inadequacy of blood filling of the canal can be seen. This probably represents a traumatic, cicatricial collapse of the canal, which may lead to post-traumatic glaucoma. Iris dialyses and PAS are also part of the post-traumatic angle morphology.

PROVOCATION TEST Due to poor sensitivity and specificity, provocation tests with PAC are only recommended for patients with subjective prodromal symptoms or with heredity where the objective examination by means of the other methods has not clarified the situation adequately. Apart from this, the provocation test is recommended for diagnostic assessment if imminent pure plateau iris conditioned PAC is suspected as in this situation, where the ACD is normal, gonioscopy remains the only method available for diagnosis (see also: Group II: Detection and diagnosis). Dark-room test – prone position With the dark-room test an introductory applanation pressure measurement is performed, and the patient is then placed in a prone position in a dark-room for at least 45 minutes. The patient is supported by the forehead, which must be pointed directly downwards. The patient must not sleep, close or press on the eyes. If a relative is not present to ensure this, another person must be present to check this, and music may be played. At the end of the test, with closed eyes, the patient is assisted to the slit lamp where a final pressure measurement is undertaken. When there is an increase in pressure of at least 8 mm, the test is regarded as positive. At the time of the test, the patient should not be receiving any form of anti-glaucomatous treatment. The provocation test in the form of dark-room test – prone position was, however, only positive in 24% of the eyes which later developed manifest PAC. Therefore it

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was concluded that the method cannot generally be recommended as a predicative test for performing an iridotomy17.

ULTRASOUND BIOMICROSCOPY (UBM) UBM is a high frequency ultrasound examination of the anterior segment of the eye as the enlargement is sufficient for assessing details in the anterior and posterior chambers (fig. 17). The resolution is 40 micron, i.e. it is possible to visualise the zonula threads. The penetration depth is only 4 mm, and therefore the examination does not reveal any retrolenticular details. A large eye cup has to be used and unintended indentation with risk of misinterpretation of the results must be avoided.

Fig. 17. UBM of chamber angle area in a normal person. P. Kock Jensen and Svend V. Kessing, The Glaucoma Clinic, Copenhagen University Hospital.

The method has created possibilities for a better pathogenitical understanding of several diseases localised in the anterior segment of the eye, not least within the field of glaucoma disorders (primary and secondary angle closure, pigmentation glaucoma, ciliary block (malignant glaucoma)).

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The UBM method has proved to be ideal for the examination and interpretation of the pathoanatomy that exists in primary angle-closure and especially in plateau iris conditioned PAC. Fig. 23 shows an example of this (UBM with typical plateau iris anatomy). UBM is thus suitable for determining the pathogenesis in difficult angle-closure cases. However, it must be emphasized that the examination is difficult to carry out in the proper manner (at right angles to the ocular surface) and it is not without some discomfort for the patient.

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Main classification of PAC 49

MAIN CLASSIFICATION OF PAC INTRODUCTION Von Gräfe (1859, see Barkan9) was the first to distinguish between “chronic” and “acute congestive” glaucoma (the latter group undoubtedly contained a mixture of both acute PAC and “haemorrhagic”/ ”inflammatory” conditions). Following Otto Barkan’s9 systematization of gonioscopy in 1938, it became possible to objectively classify the various glaucoma conditions that exist. He proposed a gonioscopically based classification of open and closed-angle glaucoma. At the same time, he recognised the mechanism in pupil block and the influence of the iridectomy on this. This was not, however, generally accepted until the 1950s. The work of Barkan was to a high degree inspired by the studies of the Swedish ophthalmologist Bengt Rosengren (1930-1931) concerning the relationship between the axial chamber depth and acute glaucoma. However, angle-closure due to plateau iris was not described until 1958 by Rosengren’s colleague Ragnar Tørnquist12, and it is only in the last decade that this form of PAC has generally become accepted as representing an important clinical entity. Therefore, no clear diagnostic criteria for this condition can be found in the glaucoma literature. Finally, it should be noted that it is only in recent years that there has been a wider interest in the detection, thorough clinical classification and specific treatment of PAC cases. There are several possible explanations for this: 1. Until 1978 when beta-blocker agents first became available world-wide, the drug treatment of open angle glaucoma and PAC were identical, i.e. pilocarpine drops. Moreover, acute glaucoma presented itself with an acute onset. As the frequent occurrence of asymptomatic “creeping” angle closure was not fully documented, the need for detection and classification with a view to specific treatment was mostly purely academic. Today, as the number of “non-miotic” glaucoma eye drops is so manifold that the use of pilocarpine can generally be avoided, the need for

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Main classification of PAC

adequate classification prior to starting treatment has become essential. 2. With the documentation of the usefulness of LCD assessment as a PAC detection method in 198831 and following the development of YAG-laser iridotomy in 198413 and argon-laser iridoplasty in 197914, a basis both for the detection of and for the uncomplicated preventive treatment of PAC was laid. 3. As mentioned in the introduction new population studies show that the world-wide visual disability from PAC is proportionally greater that from POAG due to the high prevalence of PAC glaucoma in Asians and Indians30, 40. The description primarily connected with angle-closure refers to the congenital pathoanatomical risk factors mentioned below and can be regarded as the opposite of the acquired risk factors in the secondary types of angle-closure (inflammatory and rubeosis conditioned PAS, lens luxation, ciliary block, etc.). Therefore, we define primary angle-closure (PAC) as a condition with either imminent or manifest angle-closure due to congenital, specific pathoanatomical conditions. As accounted for in the introduction, the use of the term glaucoma will be confined to conditions where there is either a permanently increased eye pressure due to peripheral anterior synechiae (latent glaucoma) or where this is combined with classical structural and/or functional glaucoma defects (manifest glaucoma).

MAIN CLASSIFICATION AND METHODS OF CLASSIFICATION As appears from fig. 18, PAC can be classified by means of gonioscopy and axial chamber depth measurement (ACD) into 3 main groups: Group I.

PAC with pupil block

Group II.

PAC with plateau iris

Group III.

PAC mixed group (I+II)

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Gonioscopy is not only the necessary diagnostic tool as far as PAC is concerned; it is also important in the classification of PAC, as gonioscopic assessment of both iris contour and mobility with the Posner lens (ref: Gonioscopy, 1. Iris contour and iris mobility, p. 33) constitutes the basic means of differentiating between the three main groups. The above-mentioned main classification may, though, be difficult to perform adequately without the simultaneous use of ACD measurement. As stated in the chapter concerning axial chamber depth (p. 11), ACD assessment is not only of diagnostic importance in connection with the pupil block conditioned PAC form, but is also a necessary supplement in order to distinguish the three clinical PAC main groups with regard to their specific treatment. The above-mentioned application of two combined methods of examination (gonioscopy and ACD: combined risk-factors) for diagnosis and classification of early PAC in order to achieve adequate indications for specific treatment corresponds exactly to the recommendations in connection with open-angle glaucoma (Danish Glaucoma Society, 199721: Combined risk-factors as diagnostic criteria for latent POAG). I. PAC with pupil block

II. PAC with plateau iris

1: Narrow angle with convex-mobile iris (indentation gonioscopy)

1: Narrow angle with flat, immobile iris (indentation gonioscopy)

2: Axial chamber depth: ≤ 2.0 mm

2: Axial chamber depth: ≥ 2.5 mm

III. PAC mixed group (I+II) 1: Narrow angle with convex/flat, mobile/immobile iris (indentation gonioscopy) 2: Axial chamber depth: ≥ 2.1 mm and ≤ 2.4 mm

Fig. 18. Main classification of PAC.

The specific treatment within the three main groups varies with the stage of PAC development, and the three main groups are therefore subdivided. Each of the main groups is subclassified in the same 6 PAC stages of development defined by means of identical objective criteriae. The terminology and definition of the individual subgroups therefore are the same in groups I, II and III (Fig.19). On the other hand, the recommendable, specific treatment of each individual subgroup differs in the three main groups. In order to

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SUBCLASSIFICATION (definitions: see p. 53) A: Suspected PAC B: Imminent PAC C: Acute/subacute PAC D: Chronic PAC E: Latent PAC glaucoma F: Manifest PAC glaucoma

A: Suspect PAC B: Imminent PAC C: Acute/subacute PAC D: Chronic PAC E: Latent PAC glaucoma F: Manifest PAC glaucoma

A: Suspect PAC B: Imminent PAC C: Acute/subacute PAC D: Chronic PAC E: Latent PAC glaucoma F: Manifest PAC glaucoma

CLASSIFICATION

I: PAC with pupil block 1: Narrow angle with convex, mobile iris (indentation gonioscopy) 2: Axial chamber depth ≤ 2.0 mm

II: PAC with plateau iris 1: Narrow angle with flat, immobile iris(indentation gonioscopy) 2: Axial chamber depth: ≥ 2.5 mm

III. PAC mixed group (I+II) 1: Narrow angle with convex/flat? Mobile/immobile? iris (indentation gonioscopy) 2: Axial chamber depth: ≥ 2.1 mm and ≤ 2.4 mm

7

Ref: Kessing SV, Thygesen J. Primary angle-closure and angle-closure glaucoma. 2007.

Temporal limbal chamber depth ≤ 0.25 mm (van Herick)

DETECTION

Flow chart for specific treatment of primary angle-closure

A: Control without treatment B: Iridotomy/iridoplasty? (gonioscopy) C: Acetazolamide, pilocarpine, betablocker, alpha2-agonist, glycerol, iridotomy/iridoplasty? (gonioscopy) D: Iridotomy/iridoplasty? (gonioscopy) E: Iridotomy/iridoplasty? (gonioscopy) Post-laser drug treatment (pilocarpine?). Possibly cat. operation F: Maximum drug treatment including pilocarpine (± iridotomy/iridoplasty)/filtrating operation

A: Control without treatment B: Iridoplasty (direct with Abraham lens) C: Acetazolamide, pilocarpine, betablocker, alpha2-agonist, glycerol, iridoplasty D: Iridoplasty E: Iridoplasty. Post-laser drug treatment (pilocarpine?) F: Maximum drug treatment including pilocarpine ± iridoplasty)/ filtrating operation

A: Control without treatment B: YAG iridotomy C: Acetazolamide, pilocarpine, betablocker, alpha2-agonist, glycerol, YAG iridotomy D: YAG iridotomy E: YAG iridotomy. Post-laser drug treatment (not pilocarpine). Possibly cat. operation F: Maximum drug treatment including pilocarpine (± iridotomy)/ filtrating operation

SPECIFIC TREATMENT

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facilitate the use of specific treatment with an expected adequate effect a recommendable procedure therefore is attached to each individual subgroup concerned (Fig.19). As stated in the introduction of this book, we define specific treatment as a procedure which, guided by the findings from the initial objective examination, is adapted to the observed specific pathoanatomy and PAC development stage of each individual eye. The main classification, subclassification and specific treatments are illustrated in a schematic flow chart (fig. 19). It should be noted that the authors have used the described classification procedure in practice throughout several decades25. The classification is alone based on the most typical, objective changes found in each main group and individual subgroup. Therefore it should be emphasized that the purpose of the present book is not an epidemiological description of the various more or less frequently found PAC manifestations based on both subjective symptoms and objective signs. The use of the combined diagnostic methods (standardised PAC gonioscopy and ACD), the definitions of subclassifications and the attached specific treatments are not specifically to be found in the literature.

← Fig. 19. Flow chart for specific treatment of primary angle-closure. Definitions, subclassification: A: Suspect PAC: Narrow, occludable in the upper sector, not lower, no PAS. B: Imminent PAC: IOP < 24 mmHg (pressure top), narrow occludable or appositional-closed upper sector and occludable lower sector, no PAS. C: Acute/subacute PAC: Temporary IOP ≥ 24 mmHg, appositional angle closure involving 360 degrees. D: Chronic PAC: IOP < 24 mmHg, PAS < 50% of the angle circumference. E: Latent PAC glaucoma: IOP permanent ≥ 24 mmHg, > 50% PAS < 80-90% of the circumferens, no structural optic nerve/retina changes or visual field defects. F: Manifest PAC glaucoma: IOP permanent ≥ 24 mmHg, PAS > 80-90%, structural optic nerve/retina changes and/or visual field defects.

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Main groups and subclassification of PAC 55

MAIN GROUPS AND SUBCLASSIFICATION OF PAC GROUP I: PAC WITH PUPIL BLOCK PAC with pupil block is by far the most common form of PAC since this group is believed to make up approx. 90% of the PAC population15. However, it should be emphasized that no accurate population studies concerning these conditions have been carried out. Pathophysiology and pathogenesis As already mentioned, in a normal eye part of the iris lies in contact with the anterior surface of the lens. This relative pupil block causes a minimal pressure gradient between the anterior and posterior chambers. This pressure gradient increases throughout life as the lens increases in size. This lens growth increases not only the iris contact area, but also the problematic sphincter iris/ lens contact. The increased pressure gradient affects the thin and elastic iris root more than it affects the central part of the iris. The normal iris surface is therefore typically slightly forward convex in configuration (ref: Normal anatomy of the chamber angle, 1. Iris contour and iris mobility). In connection with PAC, this normal slight pupil block is increased (fig. 20), leading to a pathological accumulation of aqueous fluid in the posterior chamber with a pronounced frontally convex iris and a narrow chamber angle. The aqueous accumulation explains the extreme iris mobility on indentation gonioscopy (see fig. 14). The therapeutic iridotomy equalizes the abnormal pressure gradient between the posterior and anterior chambers, flattens the iris and opens the chamber angle where possible. In these eyes, a number of bilateral anatomic features of various degrees are the basis of the abnormal pupil block. These features are more frequently seen in females than in males (F: M – 3:1) and increase with age until around 60-70 years. The eyes are most often hypermetropic with a short axial length and ACD, small cor-

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Main groups and subclassification of PAC

neal diameter, thick iris root, large ciliary body and, furthermore, with a thick lens. As mentioned above, the lens grows throughout life (decreasing ACD), and since the lens is already attached more anteriorly in the typical PAC eye than in the normal eye, the increasing iris/lens contact may lead to a pathological relative pupil block with age. In twilight conditions, an increased iris convexity due to submaximal pupil dilatation may then lead to appositional angle closure and acute or chronic “creeping” PAC. In connection with maximal pupil dilatation, the relative pupil block is, however, either diminished or even eliminated, whereas it is increased when using strong miotics, especially the irreversible miotic agents such as phospholine iodide. The latter may therefore lead to a so-called paradoxical increase in pressure in PAC cases.

Fig. 20. Imminent PAC with pupil block.

In the rarely found nanophtalmos condition (nanos = dwarfism) the above-mentioned biometric conditions are extremely pronounced, and the risk of PAC development is very high (especially the asymptomatic “Creeping” chronic PAC). Here, the traditional surgical PAC treatment is particularly risky because of post-operative “uveal effusion” and ciliary block. Nanophtalmos is especially to be suspected in very small eyes (axial length: < 20 mm) with thick sclera, small corneal diameter (< 11 mm), hypermetropia of 8D or more and extremely narrow chambers because of the normal lens size in these patients. However, quite a number of people have some of the described anatomy and yet do not develop PAC17. Therefore unknown trigger factors – psychological or physical – seem to play a part in the

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development of manifest angle closure (e.g. increased blood flow in the ciliary body). Detection and diagnosis The method of detection at PAC with pupil block involves the assessment of the limbal chamber depth (LCD). It is recommended that this efficient screening method be used on a routine basis for all new patients in the clinic. In connection with iris/corneal contact in just one single area, a subsequent gonioscopy will almost always verify the PAC diagnosis. The preliminary gonioscopic diagnosis of the narrow angle is, as previously mentioned, based on the lack of visibility of the pigmented trabecular meshwork under standardised examination conditions (ref: Standardised PAC gonioscopy methodology). In order to be able to perform specific treatment in such a PAC case, it is then necessary to ascertain the presence of any pathological pupil block. As indicated in fig. 18, this is done by diagnosing the pathological frontally-convex iris contour with extreme iris mobility, which results in the opening of the angle on indentation gonioscopy (ref: Iris contour and iris mobility). The gonioscopic pupil block diagnosis can then be verified by measuring the axial chamber depth (ACD). Especially in connection with a difficult gonioscopy (e.g. with a blurred cornea), bilateral ACD measurements are important. In the majority of cases of PAC with pupil block, bilateral ACD measurements of < 2.0 mm will be found (ref: ACD measurement, p. 12). As the degree of narrowness of the goniscopically diagnosed narrow angle cannot be measured directly, it is rational to have a quantitatively indirect measurement for the size of the chamber angle by means of ACD. Moreover, a considerable difference in the ACD value (> 1.0 mm) between the two eyes is of diagnostic importance in differentiating secondary angle-closure (SAC) from PAC. In almost half of the cases of acute PAC there are prodromal attacks (subacute PAC) with headache, blurring of vision and the characteristic appearance of haloes or rainbows around lights due to brief, mild increases in pressure with slight oedema of the cornea. This is typically caused by mydriasis in a semi-dark environment, followed by pupil contraction when the lighting conditions are increased or accommodation becomes activated (ref: subacute PAC with pupil block).

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However, it is important to underline that most eyes develop asymptomatic “creeping” chronic PAC with PAS without any acute subjective symptoms. This most likely happens to patients with an increased tendency to angle inflammation leading to PAS in relation to appositional closure of the upper angle sector (ref: Glaucoma pathology in the chamber angle, PAS). “Creeping” PAC constitutes 2/3 to 3/5 of all pupil block conditioned PAC cases17, 34, 35 . As visual loss due to PAC especially seems to be caused by this asymptomatic form, the importance of early detection is emphasized41. Cases of latent or manifest PAC glaucoma without prodromal symptom may further be misdiagnosed as representing open-angle glaucoma and thus be incorrectly treated with beta-blocker agents. This form of treatment does not prevent the formation of synechiae and may therefore result in the development of terminal PAC glaucoma. This situation further demonstrates the importance of PAC detection by means of limbal chamber depth assessment (LCD). Subclassification with specific treatment and case histories The subclassification of PAC with pupil block and the objective criteria (definitions) for each of the subgroups appear from fig. 21. Further, the recommendable, different specific treatment is attached to each subgroup. This permits the possibility of a satisfactory course of treatment without any unpleasant surprises for either the patient or the doctor. A In suspect PAC (suspicio angulo clauso) with pupil block the angle is narrow, occludable in the upper sector, but not the lower one. This is, as mentioned previously, due to the normal angle always being narrowest in the upper sector, i.e. the development of the occludability has not yet spread to the lower angle area. Control without treatment after patient information concerning prodromal glaucoma symptoms is adequate. Control is advisable after 6-12 months with regard to any change on gonioscopy or ACD.

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Main groups and subclassification of PAC 59 SUBCLASSIFICATION A: Suspect PAC with pupil block B: Imminent (threatening) PAC with pupil block

C: Acute/subacute PAC with pupil block

D: Chronic PAC with pupil block E: Latent PAC glaucoma with pupil block

F: Manifest PAC glaucoma with pupil block

DEFINITIONS A: Narrow occludable angle in the upper sector, not in the lower. No PAS B: Occludable/appositional closed upper sector and occludable lower. No PAS. IOP < 24 mm Hg (peak IOP) C: Appositional angle closure involving 360 degrees. Temporary IOP ≥ 24 mmHg D: PAS < 50% of the angle circumference. IOP < 24 mmHg E: > 50% PAS < 80-90% of the circumference. IOP permanently ≥ 24 mmHg. No structural or functional glaucoma defects F: PAS > 80-90% + structural optic nerve/retina defects and/or visual field defects. IOP permanently ≥ 24 mmHg

SPECIFIC TREATMENT A: Control without treatment B: YAG iridotomy

C: Acetazolamide, pilocarpine, betablocker, alpha2agonist, glycerol, YAG iridotomy D: YAG iridotomy

E: YAG iridotomy. Post – laser drug treatment (not pilocarpine), possibly cat. operation F: Maximum drug treatment including pilocarpine/ (± iridotomy)/ filtrating operation

Fig. 21. Subclassification of Group I: PAC with pupil block and specific treatment.

B In imminent (threatening) PAC (angulus clausus imminens) with pupil block the angle is narrow occludable or appositional closed in the upper sector and occludable in the lower, but without PAS. The patient can thus in advance be informed that YAG iridotomy (fig. 21) probably will be curative in this situation. This represents the ideal situation as the adequate glaucoma prophylaxis available will result in not only personal psychological advantages, but also practical insurance benefits for the patient. Control is advised the day following laser treatment after 1, 3 and 6 months and thereafter annually. C Acute/subacute PAC (angulus clausus acutus/subacutus) with pupil block is conditioned by trabecular meshwork occlusion due

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to appositional angle closure involving 360 degrees. This leads to varying degrees of the classical subjective symptoms due to the acute IOP increase: Blurring of vision with ciliary radiating pain to the forehead and cheek combined with general discomfort with nausea and vomiting. The acute PAC is in almost half of the cases preceded by twilight-conditioned temporary subacute PAC attacks in the form of rainbow coloured haloes around light sources (corneal oedema) with slight blurring of vision and frontal headaches. Unless the manifest acute PAC attack is treated adequately within the first 24 hours, various degrees of pressure-conditioned ischaemic damage in the form of multiple retinal ischaemic infarcts may arise. In rarer cases, this situation will include varying degrees of optic nerve head lesions. The accompanying multiple retinal microhaemorrhages and dilated veins may be interpreted as representing an initial central vein thrombosis. Long-standing hypertension with associated ischaemia may result in hypotonia due to a reduced aqueous production, and this may give rise to further confusion with regard to the correct diagnosis. This hypotonia may further lead to false optimism regarding treatment, increasing the risk of overlooking advanced PAC cases with acute pressure worsening. Again, it is necessary to stress the importance of adequate gonioscopy, which should generally be carried out after using 50% glucose drops for clearing the oedematous cornea, as a necessary basis for the specific treatment of these cases. If the cornea remains cloudy in spite of the 50% glucose drops and it is therefore not possible to establish a definite diagnosis in the affected eye, the PAC diagnosis can always be established by performing limbal and axial chamber depth examinations as well as a gonioscopic evaluation of the patient’s healthy eye. This is due to the fact that the anatomical risk factors are always present bilaterally in PAC even though they are most pronounced in the acutely affected eye3. Finally, it is good clinical practice to always begin an objective examination with the least discomfort to the patient, i.e. always start with an ACD assessment and a gonioscopy examination in acute PAC in the healthy eye. The examination of the other eye is also essential with regard to determining the indication for preventive iridotomy (remember pre-laser preventive pilocarpine treatment of the healthy eye!).

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Furthermore, a pronounced case of acute PAC will often lead to permanent objective changes in the form of pupil dilatation, sector-shaped grey iris stromal atrophy, anterior subcapsular lens opacity, “glaukomflecken”, and diffuse chamber angle pigmentation, which can support the diagnosis. “Glaukomflecken” are small, white irregular spots in the pupil area situated in the lens capsule or just subcapsularly, whereas the grey iris atrophy, which arises in the weeks following an attack, are seen as greyish areas of iridoschisis in the iris stroma. In addition, in acute PAC it is recommended that YAG-laser iridotomy be undertaken as soon as it is technically possibletodosoaftertheinitialmedicalpressure-reducingtreatmenthasbeeneffect uated(ref:TreatmentofacutePAC).This is advised in order to make use of the “synecholysis effect” of the iridotomy before any irreversible, organised PAS have been formed. For the same reason, steroid eye drops are to be recommended with the acute medical treatment of PAC. Pressure control and gonioscopy should be undertaken the day following laser treatment as well as after 1, 3 and 6 months to ensure that it is not a question of acute IOP increase in a case of advanced PAC requiring a different therapy. Thereafter, control examination should be performed annually. As mentioned above, cases of abortive subacute PAC with prodromal symptoms (rainbow coloured haloes, blurred vision and frontal headaches) are frequently seen. Early diagnosis and treatment can be performed by the observant ophthalmologist. D Contrary to general assumption, asymptomatic, “creeping” chronic PAC (angulus clausus chronicus) with pupil block is more common than acute PAC17, and this represents one of the most important arguments for carrying out PAC detection using LCD assessment. The term “chronic” refers to the identification of permanent structural changes in the form of PAS, but here only involving < 50% of the angle circumference (fig. 21). This means that the remaining angle drainage will generally be adequate to maintain normal eye pressure without any treatment. It is to be emphasized that the occurrence of a single but definite PAS formation in the upper angle should be considered as represent-

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ing a solid basis for chronic PAC diagnosis and consequently an indication for treatment. The treatment consists of YAG-laser iridotomy (fig. 21), and the patient can be informed before laser treatment that the treatment in itself will probably be curative. Apart from control the day following laser treatment, the patient should be checked after 1, 3 and 6 months. Then generally annually in order to ensure that it does not represent a case of latent PAC glaucoma. Post-laser gonioscopic examination is especially indicated in border-line cases as it then becomes much easier to determine the degree of PAS development and thereby the risk of development of permanent pressure elevation. E In latent PAC glaucoma (glaucoma angulo clauso latens) with pupil block the untreated eye pressure is permanently ≥ 24 mmHg due to PAS formations in 50 to 80-90% of the angle circumference. There are, however, no structural glaucoma changes in the posterior pole, no functional glaucoma defects and most often without subjective symptoms. If the gonioscopic assessment has been correct, the eye pressure will, also following YAG-laser iridotomy, remain permanently increased with the risk of the development of structural/functional defects, i.e. manifest glaucoma. Due to the combined risk factors (ocular hypertension + PAS), this risk is considered to be large enough to warrant permanent, prophylactic, medical IOP reduction, notably only without the use of pilocarpine (fig. 21). As with POAG, it is advisable to check the patient at regular intervals of 4-5 months with special emphasis on the gonioscopic assessment of the degree of development of PAS. In most cases, the latent PAC glaucoma will develop subclinically from asymptomatic “creeping” chronic PAC, leading to a risk of misdiagnosis, often in the form of latent POAG with consequent unspecific treatment in the form of various non-miotic eye drops. It is important to stress that such treatment does not prevent a continued development of PAS with a gradually increasing pressure and consequently a risk of manifest PAC glaucoma or neovascular glaucoma. The importance of routine LCD assessment followed by ACD measurement and standardised PAC gonioscopy at the slight-

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Main groups and subclassification of PAC 63 Case report 1

Latent PAC glaucoma with pupil block left eye followed by neovascular glaucoma, imminent PAC with pupil block right eye Referral diagnosis given by the patient’s ophthalmologist: Glaucomatous iritis left eye. A 50-year-old woman was referred after one month of treatment of glaucomatous iritis with suspect iris rubeosis: Diagnosis given by the ophthalmological department:

Neovascular glaucoma left eye without known pathogenesis. Squint amblyopia left eye.

Slit lamp and ophthalmoscopy of the right eye showed no abnormality. In the left eye, an IOP of 38 mmHg was found, the anterior chamber was slightly flattened, but with an open angle on gonioscopy. Iris rubeosis was present, and ophthalmoscopy revealed a normal fundus without thrombosis. Treatment:

Panretinal argon-laser photocoagulation x 2 left eye.

Due to a continuously raised IOP (48 mmHg), in spite of treatment with timolol, dorzolamide, latanoprost and dexamethasone left eye, the patient was referred to the Glaucoma Clinic. Diagnosis given by the Glaucoma Clinic:

Latent PAC glaucoma with pupil block left eye. Neovascular glaucoma left eye. Imminent PAC with pupil block right eye.

The right eye showed LCD < 0.25, ACD 1.8 mm, IOP 15 mmHg without treatment and a narrow occludable angle without PAS as well as an anterior convex iris with pronounced iris mobility. C/D ratio 0.2 without structural changes. In spite of pilocarpine treatment, the patient developed subacute PAC with IOP 37 mmHg prior to YAG iridotomy. The left eye showed LCD < 0.25 mm with iris/corneal contact, ACD 1.7 mm and a synechiae-closed angle in the entire circumference with an inactive rubeosis as well as a medium dilated pupil with pupil synechiae. Vertical C/D ratio 0.2 without structural changes and a normal fundus without signs of thrombosis and with marked retinal laser burns. Treatment:

Right side: YAG-laser iridotomy. Left side: Mitomycin trabeculectomy Followed by transscleral diode laser cyclophotocoagulation due to lack of effect. Subsequently, a normal IOP on treatment with timolol and brinzolamide with a stable visual acuity of 6/24 (0.25). Comments Reason for unspecific treatment: No LCD and ACD assessment and no gonioscopy right eye. Misinterpretation of gonioscopy left eye. Outcome of unspecific treatment: Development of neovascular glaucoma because of undiagnosed latent PAC-glaucoma with pupil block treated as secondary open-angle glaucoma.

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est suspicion of PAC should be emphasized. The examination of the healthy eye is particularly important in this connection. This is illustrated in the case report below (case report 1). In some cases, asymptomatic latent PAC glaucoma, especially during the later course, will lead to subacute IOP increase with subjective symptoms in the form of slight blurring of vision and frontal headaches, but usually without corneal oedema. Consequently, with an inadequate gonioscopy without pre-laser observation of the PAS formation, there is a risk that the condition will be seen as a first-time case of subacute PAC followed by use of unspecific treatment. F Manifest PAC glaucoma (glaucoma angulo clauso manifestus) with pupil block refers to the PAC development stage in which structural changes to the optic nerve and the retinal nerve fibre layer are seen, often combined with visual field defects. The untreated IOP is high (> 30 mmHg) as a result of PAS involving > 80-90% of the angle circumference, but most often the condition is without subjective symptoms. When PAS can be identified in the entire angle circumference (approx. 360 degrees) with a reasonable degree of certainty, then neither YAG iridotomy nor cataract removal (without simultaneous trabeculectomy) can be expected to result in any form of pressure reducing effect, but rather lead to a further pressure rise due to increased inflammation and consequently with a poorer prognosis for a fistulating operation. This is partly due to the fact that it is not possible to disrupt fibrozised PAS by means of an iridotomy or by removing the lens and partly due to the fact that the remaining, functioning trabecular meshwork may become occluded by iris particles formed through either laser treatment or from viscoelastic material and inflammation precipitates in association with a cataract operation. At this stage of development of the disease process, it is only advisable to perform an iridotomy or remove a cataract when indentation gonioscopy shows a high degree of uncertainty as to the degree of spreading of PAS, and only when the patient has been given maximum drug treatment. Furthermore, the degree of glaucomatous loss of tissue in the nerve head may be used as a guideline since a C/D ratio of 0.9

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in the affected eye will almost always be accompanied by PAS in most of the circumference. The same applies to the occurrence of tunnel vision in automatic perimetry, which is why this examination should also generally be carried out prior to the planning of the final treatment. In terminal PAC glaucoma (C/D ratio 0.9 and/or tunnel vision) YAG-laser iridotomy or removal of the lens without simultaneous filtrating operation is therefore contraindicated. It must therefore be stressed that a reasonably adequate ophthalmoscopic optic nerve assessment should always be carried out prior to laser treatment. This will involve use of 50% glucose in order to clear the cornea and possibly pupil dilatation with 2.5% metaoxedrine drops because of drug miosis (pilocarpine treatment). When a peak pressure > 20 mmHg despite maximum drug treatment including use of pilocarpin is observed, or when the patient cannot handle the treatment using three eye drop medications (the definition of maximum treatment), a fistulating operation should be performed (in case of cataract combined phaco-MMC- trabeculectomy). Only one clinical retrospective examination concerning this has been reported33. YAG iridotomy operations were performed on eyes with manifest PAC glaucoma, but in all cases there was an indication for continued medical treatment, and in more than 1/3 a filtrating operation was required. Especially in connection with PAC glaucoma with pupil block the risk of post-operative ciliary block (formerly known as malignant glaucoma) may be increased (ref: Treatment procedure: Fistulating operation). If the pressure is acceptable on maximum treatment (including pilocarpine), the patient should then remain on the medication. For the same reason, in cases where IOP > 20 mmHg in an only eye with terminal manifest PAC glaucoma, transscleral diode-laser cyclophotocoagulation is recommendable instead of a fistulating operation. As with latent PAC glaucoma, with manifest PAC glaucoma there may occasionally be subacute IOP increase with frontal headaches and slight blurring of vision, however with an almost clear cornea. This situation may be misinterpreted as a true attack of acute glaucoma with the indication for a “curative” iridotomy and so resulting in unspecific treatment.

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Case report 2

Manifest juvenile glaucoma misinterpreted as manifest PAC glaucoma with pupil block Referral diagnosis given by the patient’s ophthalmologist:

Not given.

A 42-year-old man with headache attacks on the right side of the head and with pains around the right eye throughout the last six months. Goldmann applanation 45/21 mmHg untreated. Normal slitlamp examination and an excavated optic disc of the right eye. Treatment:

Timolol and dorzolamide eye drops.

Due to a Goldmann applanation of 45 mmHg in the right eye in spite of treatment and suspect PAS on gonioscopy, the patient was referred to the ophthalmological department after additional treatment with pilocarpine and acetazolamide 500 mg twice daily. Diagnosis given by the ophthalmological department:

Chronic closed angle glaucoma

ACD assessed as normal subjectively, however not measured objectively. Gonioscopy revealed: “Curved angles, microstructures just visible in the form of PAS”. Goldmann applanation: 24/12 mmHg on the treatment as prescribed. Optic discs with deep glaucomatous excavation. C/D ratio: 0.9/0.6”. Treatment 1: YAG-laser iridotomy right eye. The day after an IOP of 38 mmHg was found in spite of timolol, dorzolamide, pilocarpine and acetazolamide. Treatment 2: Further YAG-laser iridotomy right eye due to suspected insufficient iridotomy. The patient was then referred to the Glaucoma Clinic for gonioscopic assessment. Diagnosis given by the Glaucoma Clinic:

Manifest juvenile glaucoma on the right eye: Latent juvenile glaucoma on the left eye.

LCD = 1.00 both eyes, ACD 3.0/3.0 mm, large iridotomies and open, non-occludable angles with goniodysgenesis and pronounced iris processes, but no PAS. C/D ratio right eye 0.9 with a corresponding tunnel vision on automated perimetry. C/D ratio left eye was 0.7 without structural changes and with normal visual fields. Treatment:

Trabeculectomy with mitomycin C in the right eye because of pressure > 20 mmHg with maximum drug treatment. Following this, IOP of 17 mmHg on both eyes on treatment with latanoprost right eye and betaxolol both eyes. Comments Reason for unspecific treatment: First and foremost, because of the subjective symptoms and the high IOP. Furthermore, the pronounced iris processes (goniodysgenesis) and the corneoscleral trabecular meshwork with little pigmentation resulted in the gonioscopic misdiagnosis. Outcome of unspecific treatment: Unnecessary YAG iridotomy.

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Subacute, pressure conditioned subjective symptoms caused by juvenile open-angle glaucoma may also be misinterpreted as prodromal symptoms of acute PAC. Blurring of vision, rainbow coloured haloes and headaches are common in juvenile glaucoma16, and since goniodysgenesis, often with pronounced iris processes, is also typically seen in this form of glaucoma16 the condition may be misinterpreted as acute aggravation of manifest PAC glaucoma with diffuse PAS formation (ref: Normal anatomy of the chamber angle, The uveal meshwork). Case report 2 is an example of this. YAG-laser iridotomy: Evaluation The need for preventive YAG-laser iridotomy should be firmly established before undertaking the procedure, with a precise evaluation not only of the effect, but also of any possible complications. As previously mentioned, gonioscopic detection of a pupil block conditioned PAC risk anatomy does not necessarily mean that the patient in question will develop a manifest disease. In an American multi-centre study17 129 patients with PAC risk anatomy were monitored for up to six years without treatment, and during this period only 25 patients (38 eyes) developed manifest PAC, i.e. approx. 20% of the patients at risk. In a recent study from India43 a similar risk of progression was found (22% of eyes with occludable angles in 180 degree or more developed manifest PAC after 5 years).The estimated risk of developing manifest glaucoma in the individual eyes at risk within a period of five years was estimated at 30% (Kaplan-Meier analysis)17. Furthermore, it was concluded that the most predictive method for identifying the eyes that later developed manifest PAC was the slit lamp and gonioscopy examination carried out by the experienced ophthalmologist17. The second-best method was axial chamber depth measurement as the eyes that were developing manifest PAC had a shallower chamber depth than the eyes at risk that did not develop symptoms17. This was not, however, significant. The provocation test in the form of dark-room test – prone position (ref: Dark-room test – prone position, Diagnostic methods with PAC) was, however, only positive in 24% of the eyes which later developed manifest PAC. Therefore it was concluded that

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the method cannot generally be recommended as a predicative test for an iridotomy17. Even though no predicative method with the desired sensitivity with respect to iridotomy indication exists, the conclusion of the study was that preventive laser treatment should be recommended for all patients with a gonioscopically verified risk anatomy17. A similar attitude was clearly expressed in 199618, 19. According to the above-mentioned statement18, 19, PAC risk anatomy is found among 5% of the population, whereas the prevalence of manifest glaucoma is 0.6%34. The situation can therefore be compared with open-angle ocular hypertension, which is found among approx. 10% of the population and primary open-angle glaucoma with a general prevalence of 0.65% in Denmark20. The guidelines concerning treatment of primary open-angle glaucoma (POAG)21 given by the Danish Glaucoma Society therefore only recommend treatment of latent POAG (without structural/functional defects) with a view to preventing manifest POAG when combined risk factors are present (ocular hypertension and inheritance, now updated with thin corneas, larger Cup-Disc ratios and older age groups according to the Ocular Hypertension Treatment Study45). Accordingly, in connection with PAC, the application of combined risk factors in the form of a narrow angle with the standardised PAC gonioscopy methodology and an axial chamber depth of ≤ 2.0 mm is therefore recommended. This recommendation is based on the fact that pupil block conditioned PAC, as mentioned in the section concerning axial chamber depth measurement, is predominantly found in eyes with an ACD ≤ 2.0 mm. In this way, the diagnostic basis for imminent PAC is further enhanced, making the indication of preventive YAG-laser iridotomy more precise. This is especially relevant in bilateral PAC, whereas the occurrence of acute PAC in the first eye creates a clear indication for preventive laser treatment of imminent PAC in the other eye since acute PAC episodes will otherwise occur in 50-75% of these eyes within five years. With respect to the effect of the prophylactic iridotomy, the laser treatment effectively eliminates the risk of angle-closure as the relative pupil block, and thereby the pathogenic basis for PAC, is removed18.

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Even though the indication and the effect of YAG-laser iridotomy thus seem to be clarified, proper use requires that serious complications be avoided. As opposed to argon-laser iridotomy, no laser-conditioned focal cataract changes have been described with YAG-laser iridotomy22, but on the basis of a theoretical risk it is recommended that the iridotomy be placed as peripherally as possible on the iris. The most frequent complication is temporary haemorrhage from the iridotomy opening. This is seen in up to 44%22, but the bleeding will cease spontaneously and can be reduced by indentation with the contact lens used. Only in cases on anticoagulation treatment or with acetylsalicylic acid medication does a sedimented hyphaema occur, and this treatment should therefore be discontinued for some weeks before laser application. 32% of eyes with haemorrhage have an IOP increase of > 10 mmHg within the first three hours after the laser treatment, but the corresponding figure for eyes without bleeding is 33%22, i.e. the bleeding does not accentuate the occurrence of post-laser increase in pressure. As stated in the chapter concerning treatment procedures, one pre-laser application with apraclonidine (Iopidine®) drops will, as well as preventing any post-laser increase in pressure, also reduce the occurrence of bleeding due to the vasoconstrictive properties of the substance. The patient should therefore receive the eye drops before the laser treatment. Otherwise no serious complications occur (ref: YAG-laser iridotomy, p. 102), and consequently it can be concluded that the advantages of preventive YAG-laser iridotomy with imminent PAC clearly outweigh the disadvantages, and the treatment can therefore be recommended. YAG-laser iridotomy in general The recommended technique for YAG-laser iridotomy is described in the chapter concerning treatment procedures, and therefore only the more general conditions will be discussed in this chapter. There has been a tendency to perform several iridotomies in the same eye just to be on the safe side! However, there is no rational basis for this. According to Hagen-Poiseuilles’ law, an opening of about 60 microns should compensate for the normal aqueous flow23. A stro-

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mal iridotomy opening of about 150 microns should thus be fully adequate to neutralise the pressure gradient between the anterior and posterior chambers in pupil block conditioned PAC22,24. It is possible to obtain an impression of the size of the iridotomy opening by projecting the 0.2 mm “spot” from a Haag-Streit slit lamp on the iridotomy or by using the 100 micron “aiming spot” from the argon-laser. Apart from a stromal hole of > 100 microns, adequate iridotomy function also requires an opening through the iris pigment epithelium. This is ensured by means of co-axial slit lamp illumination immediately after laser treatment. As opposed to argon-laser iridotomy there is no post-laser occlusion after YAG-laser iridotomy in PAC22. By performing several iridotomies there is an additional risk that one of the iridotomies will be situated in the rima area and thus may create visual disturbances for the patient. It should therefore be recommended that a single iridotomy is placed in the peripheral iris area covered by the eye-lid in the upper direction. To ensure the peripheral localisation, 2% pilocarpine eye drops are used before laser treatment (also see: YAG-laser iridotomy technique).

GROUP II: PAC WITH PLATEAU IRIS The classification criteria for this PAC group are seen in fig. 18, which illustrates the main classification of PAC. As previously stated, eyes with plateau iris probably constitute at the most 10% of the PAC population according to clinical opinion15, and of this group eyes without a pupil block component, i.e. purely plateau iris conditioned pathogenesis, probably only constitute 25%25. However, it should be emphasised that there are no prospective population studies concerning the prevalence of plateau iris conditioned PAC, partly because there is no generally accepted definition of this PAC group. Consequently, it is quite likely that the prevalence of this group is considerably larger than generally assumed. Moreover, as the specific treatment of this group solely involves argon-laser iridoplasty, the correct diagnosis is a prerequisite for a satisfactory course of treatment. PAC with plateau iris is most frequently seen in women between 30 and 50 years15. The gender ratio is F/M: 3/125, i.e. the same gender

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distribution as in PAC with pupil block, whereas the occurrence of hypermetropy is probably less prevalent. Pathophysiology and pathogenesis The pure plateau iris configuration refers to a pathoanatomy with narrow angle, but with normal axial chamber depth (ACD ≥ 2.5 mm) as is seen in the main classification figure (fig. 18, p. 51). The angle is narrow because of two conditions as is seen in fig. 22.

Fig. 22. PAC with plateau iris: Undilated/dilated pupil.

First of all, the iris is inserted right at the anterior edge of the ciliary body directly behind the scleral spur, i.e. the iris stroma often covers the longitudinal fibres of ciliary muscle (the ciliary band) on their course to the scleral spur. This implies that the normal angle recess (the most peripheral point of the chamber angle) is small and that it is more difficult to identify the ciliary band than in PAC with pupil block (cf. fig. 20 and fig. 22). Secondly, the iris is flat and almost immobile with an angled iris root, which makes the iris knee abnormally prominent and impossible to level out by means indentation gonioscopy (fig. 14). This means that the visualisation of the normal angle structures remains unimproved on indentation gonioscopy, which is quite the opposite to pupil block conditioned PAC (ref: Iris contour and mobility, p. 33).

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Fig. 23. UBM with typical plateau iris anatomy in spite of iridotomy (top, left picture) in a patient (case report 7) with chronic PAC with PAS (lower, right picture). P. Kock Jensen and Lars Solander, the Glaucoma Clinic, Copenhagen University Hospital.

Due to this special pathoanatomy, a semi-dilated pupil can lead to angle-closure (e.g.: darkened room). The pathogenesis for this anatomy is probably a prominent anteriorly positioned ciliary body7 as shown in the UBM pictures in fig. 23. These ultrasound pictures are taken of a patient with recurring subacute attacks in spite of YAG-laser iridotomy (case report 7). The top left picture shows the flat iris with the typically prominent iris knee, which makes the angle narrow occludable in spite of the perfect penetrating iridotomy. It should therefore be strongly emphasized that YAG iridotomy is completely ineffective in the plateau iris condition. All four pictures show an anteriorly positioned ciliary body as indicated with the arrow in the top right picture, whereas the bottom left picture shows an additional iris/ciliary body cyst. These cysts are almost always seen in plateau iris and are probably secondary to the narrow space in the posterior chamber. The anteriorly positioned ciliary body is the reason for the immobility of the iris periphery on indentation gonioscopy (chock

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effect) as opposed to the situation in connection with pupil block conditioned PAC. Here, the pathogenetic aqueous fluid in the posterior chamber is easily pushed away on indentation gonioscopy, leading to the typical extreme iris mobility for this PAC group (see fig. 14). The gonioscopic assessment of iris contour and mobility is, apart from axial chamber depth measurement, the most important differential diagnostic parameter for distinguishing between pupil block or plateau iris conditioned PAC. In connection with a pronounced plateau iris configuration where the iris knee is in line with Schwalbe’s line over the entire circumference, either spontaneous or drug-induced pupil dilatation will lead to complete appositional angle closure with acute PAC (fig. 23). However, this situation is only seldom seen15. Far more commonly, the undulating configuration of the iris knee will lead to an incomplete iris/ meshwork apposition situated at the tops of the wave crests. This pathoanatomy causes a ”creeping” PAS formation, i.e. asymptomatic PAC. Thus, asymptomatic, “creeping” angle-closure is probably far more common in connection with plateau iris than with PAC with pupil block, i.e. it is seen in most cases of plateau iris conditioned PAC15. It is especially important with plateau iris that gonioscopy is performed under dimmed illumination and using a narrow, low aperture slit beam. The reason for this is that any light-conditioned miosis, especially in plateau iris, will increase the risk of overlooking narrow angle anatomy (ref: Standardised PAC-gonioscopy methodology). Detection and diagnosis Evaluation of the limbal chamber depth (LCD) is, as in PAC with pupil block, the preferred method of detection. It is important to note that with plateau iris the LCD in some cases lies between 0.25 and 0.5, which is greater than the previously established risk factor of 0.25 (ref: LCD methods, p. 13). In detection of plateauiris conditioned PAC it is especially important to perform routine

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gonioscopy with a Posner lens when there is the slightest suspicion of a relative narrow chamber angle following LCD estimation. The diagnosis of a plateau iris configuration is relatively simple as it is purely based on the previously described characteristic pathoanatomy. The gonioscopic evaluation regarding the narrowness of the angle is, however, often much more difficult when compared to the pupil-block type. This is primarily due to the poor visibility of the trabecular meshwork and the ciliary band. In this younger group of patients the meshwork is less pigmented, and the ciliary band is often partially hidden by the iris stroma and the uveal meshwork. Furthermore, the undulating iris knee will often create the opportunity of identifying the trabecular meshwork in certain “wave-bottoms”. Diagnosis of a narrow angle with a plateau iris requires a greater degree of judgement than in PAC with pupil block. As has been emphasised, a dimmed room illumination and the weakest possible slit-lamp light are required for proper detection. Moreover, with the pure plateau iris form of PAC the normal ACD (≥ 2.5 mm) provides no diagnostic assistance. Therefore, in case of imminent PAC with plateau iris a positive dark-room test may be used in addition to the gonioscopy as an indication for treatment (see below). The necessity of using two diagnostic procedures with regard to proper diagnosis and indication for treatment concur with the previous statements made (ref: Main classification and methods of classification). A negative dark-room test in the presence of a gonioscopically suspect plateau iris configuration does not necessarily imply that the patient can be exempted from further investigations as the predictive value of a dark-room test is limited (ref: YAG-laser iridotomy: Evaluation, p. 67). However, there are no investigations regarding the predictive value of the dark-room test in PAC with plateau iris. It is to be recommended that such patients be observed without treatment until such times that either PAS or prodromal symptoms develop. Even though ACD measurements are without diagnostic significance with the pure plateau iris, it is to be noted that the examination is necessary from the differential diagnostic point of view with regard to specific treatment. A normal anterior chamber depth excludes a pupil-block component and the indication

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for YAG-laser iridotomy. In this situation with pure plateau iris only argon-laser iridoplasty is indicated. Subclassification with specific treatment and case histories As in pupil block conditioned PAC, the various stages of development of PAC with plateau iris require different forms of treatment. In plateau iris it is therefore also advisable to carry out a subclassification with attached specific treatment for each individual subgroup. The subclassification and the specific treatment are shown in fig. 24. It should be stressed that the terminology and definition of the individual clinical subgroups are the same as those of PAC with pupil block (see fig. 21), while the treatment is, however, different (specific treatment!). With a view to more detailed guidelines for the laser treatment see also the section: Argon-laser iridoplasty, p. 102. SUBCLASSIFICATION

DEFINITIONS

A: Suspect PAC with plateau iris

A: Narrow occludable angle A: Control without treatment in the upper sector, not in the lower. No PAS

B: Imminent PAC with plateau iris

B: Occludable/appositional closed upper sector and occludable lower. No PAS. IOP < 24 mmHg (peak pressure ) C: Appositional angle closure involving 360 degrees. Temporary IOP ≥ 24 mmHg D: PAS < 50% of the angle circumference. IOP < 24 mmHg E: > 50% PAS < 80-90% of the circumference. IOP permanently ≥ 24 mmHg. No structural or functional glaucoma defects

C: Acute/subacute PAC with plateau iris

D: Chronic PAC with plateau iris E: Latent PAC glaucoma plateau iris

F: Manifest PAC glaucoma with plateau iris

F: PAS > 80-90% + structural optic nerve/retina defects and/or visual field defects. IOP permanently ≥ 24 mmHg

SPECIFIC TREATMENT

B: Iridoplasty

C: Acetazolamide, pilocarpine, betablocker, alpha2-agonist, glycerol, iridoplasty D: Iridoplasty

E: Iridoplasty. Post-laser drug treatment (pilocarpine?)

F: Maximum drug treatment including pilocarpine/ (± iridotomy)/filtrating operation

Fig. 24. Subclassification of Group II: PAC with plateau iris and specific treatment.

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A In suspect PAC (suspicio angulo clauso) with plateau iris the angle is narrow occludable in the upper sector, but not the lower. As mentioned in the section: Detection and diagnosis, the gonioscopic assessment with regard to narrow angle is more difficult in plateau iris conditioned PAC than in the pupil block form. Therefore, if in doubt, a dark-room test may be carried out in order to give as accurate a diagnosis as possible. Control without treatment is recommended after the patient has been thoroughly informed about glaucoma prodromal symptoms. Generally, control should be carried out after 6-12 months – naturally sooner should subjective symptoms occur. B In imminent PAC (angulus clausus imminens) with plateau iris the angle is narrow occludable or appositional closed in the upper sector and occludable in the lower, but without PAS. Apart from gonioscopy, a positive darkroom test is generally required, because of the normal ACD and the difficulty with regard to the visibility of the trabecular meshwork (ref: Detection and diagnosis). Not until the diagnosis has been verified is it possible to decide on a preventive iridoplasty, since especially this form of laser treatment requires a precise indication due to the higher incidence of complications than with YAG-laser iridotomy (ref: Argon-laser iridoplasty: Evaluation, p. 80). Case report 3 is an example of initial misdiagnosis caused by the above-mentioned conditions with an unspecific treatment. This is, however, followed by a clarification by utilising the procedure as described. Because of the frequent presence of LCD limit values in plateau iris, the detection of early PAC cases in this main group remains less than in the pupil block group, and the degree of detection is dependant upon the use of gonioscopy even at the slightest suspicion of LCD. Precisely in this situation the more efficient gonioscopy with the Posner lens has many advantages as opposed to the more time-consuming and discomforting gonioscopy using the Goldmann lens.

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Imminent PAC with plateau iris Referral diagnosis given by the patient’s ophthalmologist:

Open-angle glaucoma. Dry AMD.

A 66-year-old female with initially detected IOP 28 mmHg right eye and subsequent timolol gel and latanoprost treatment is referred because of the limit pressure and increasing visual field defects. Diagnosis given by the ophthalmological department:

Open-angle glaucoma. AMD.

Anterior chamber was described as slightly flattened peripherally, deep centrally and open angle on gonioscopy, however with a slight plateau appearance! Because of suspicion of increasing visual field defect in spite of normal IOP on the prescribed treatment, ALT was carried out on the right eye. Because of temporary IOP of 26 mmHg in both eyes 14 days post-laser, the patient was referred to the Glaucoma Clinic due to “unmanageable glaucoma”. Diagnosis given by the Glaucoma Clinic:

Bilateral imminent PAC with plateau iris.

LCD: 0.25 right eye. > 0.25 left eye, ACD 2.5/2.6 mm. Untreated IOP < 24 mmHg. On gonioscopy: Narrow occludable angle without PAS, plateau iris with poor motility and typical peripheral iris knee. On ophthalmoscopy.: Ratio: 0.5/0.3 without certain loss of tissue. With diurnal curve untreated IOP < 24 mmHg was found. Positive prone, dark-room test (17/16 mmHg before, 28/24 mmHg after). Automatic perimetry did not show clear glaucoma changes. Treatment: Bilateral argon-laser iridoplasty Followed by normal eye pressure with negative dark-room test. Comments Reason for unspecific treatment: Incorrect glaucoma classification (primary open-angle glaucoma instead of PAC) due to inadequate gonioscopy. Outcome of unspecific treatment: 1. Prolonged process (approx. 6 months) with treatment for simplex glaucoma and temporary pressure rise because of angle closure. 2. Unnecessary argon-laser trabeculoplasty because of the above-mentioned diagnoses.

C In Acute/subacute PAC (angulus clausus acutus/subacutus) with plateau iris the clinical symptoms and signs are exactly the same as seen in the pupil block form. As in the acute pupil block form, it should be emphasized that it is important to carry out the objective examination of the healthy eye before examining the affected eye with a view to establishing a reliable diagnosis. Furthermore, the examination of the healthy eye will generally lead to an in-

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dication for preventive iridoplasty due to imminent PAC with plateau iris. Following pressure reducing acute medical treatment (ref: Treatment procedures with PAC) argon-laser iridoplasty is carried out. In contrast to YAG iridotomy this treatment can be carried out regardless of a cloudy cornea. D Asymptomatic “creeping” chronic PAC (angulus clausus chronicus) with plateau iris is probably seen far more often than the acute form, especially in main group II. Therefore, active detection by means of LCD and efficient indentation gonioscopy with the Posner lens is particularly important in connection with this subgroup. The term “chronic” as in chronic PAC with pupil block refers to the presence of PAS formations in < 50% of the angle circumference (fig. 24), i.e. the remaining trabecular meshwork function is usually adequate in order to maintain normal IOP without pressure lowering medical treatment. Thus, the diagnosis at this phase of development provides the opportunity for primary specific iridoplasty without the need for post-laser medical treatment. Therefore, the patient can be given pre-laser information that the laser treatment will most likely be curative. Control is advised the day after laser treatment and 1, 3 and 6 months later with respect to supplementary iridoplasty, which is often necessary in order to obtain maximum angle opening. Following this, the patient is seen once a year for a gonioscopic assessment of the iridoplasty effect as supplementary laser treatment may be necessary with some patients (ref: Argon-laser iridoplasty: Evaluation). It should be stressed that YAG laser iridotomy does not change the angle anatomy. Case report 4 illustrates the typical subclinical course as well as the lack of effect of YAG laser iridotomy in group II. E In latent PAC glaucoma (glaucoma angulo clauso latens) with plateau iris the untreated IOP is permanently ≥ 24 mmHg because of PAS formations in 50% to 80-90% of the angle circumference,

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Bilateral chronic PAC with plateau iris Referral diagnosis given by the patient’s ophthalmologist:

Not given.

A 71-year-old man with untreated Goldmann applanation 28/26 mmHg without subjective symptoms and with occludable angles with plateau characteristics as well as normal optic nerve heads, receiving Dorzolamide treatment, was referred for YAG-laser iridotomy. Diagnosis given by the ophthalmological department:

Bilateral latent PAC glaucoma with suspicion of plateau iris.

Goldmann applanation.: 22/22 mmHg on dorzolamide treatment, angles narrow, occludable in the upper/lower areas, no PAS but plateau characteristics with LCD 0.25 both eyes, ACD 2.7 mm both eyes and C/D ratio 0.4/0.5 without certain structural changes. Treatment:

Bilateral YAG laser iridotomy and discontinued anti-glaucomatous treatment.

Due to untreated IOP 23 mmHg right eye, the patient was referred to the Glaucoma Clinic. Diagnosis given by the Glaucoma Clinic: Bilateral chronic PAC with plateau iris. LCD 0.25 both eyes and ACD 2.6 both eyes. In spite of adequate bilateral iridotomies, narrow, occludable angles with immobile irides with iris knee and PAS in the upper area were found in both eyes as well as C/D ratio 0.6/0.5 without structural changes, and normal visual fields with automatic perimetry. Treatment:

Pilocarpine 2 % x 4 both eyes and bilateral. argon-laser iridoplasty

Followed by diurnal curve showing: peak pressure 19/18 mmHg, without medical treatment, i.e. satisfactory untreated situation. Control was recommended at the local ophthalmologist one month later for potentially further iridoplasty treatment. Comments Reason for unspecific treatment: 1. Uncertain Goldmann gonioscopy with a suspicion of plateau iris, but no Posner lens gonioscopy with regard to PAS and iris mobility assessment. 2. No consequence of the ACD measurement. Outcome of unspecific treatment: Unnecessary YAG iridotomy with unchanged post-laser narrow angle instead of primary argon-laser iridoplasty, i.e. patient-stressing “trial and error” course.

but without structural glaucoma changes in the posterior pole and without visual field defects. Even after satisfactorily performed primary iridoplasty the IOP will still be permanently increased. Because of the risk of the patient developing manifest glaucoma,

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permanent medical treatment is therefore still indicated. In most cases, the use of pilocarpine is, as opposed to the situation concerning pupil block, necessary to ensure IOP < 20 mmHg (ref: Argon-laser iridoplasty: Evaluation). As in POAG, pressure and gonioscopy control is advised every four to five months. The latent PAC glaucoma with plateau iris will probably develop asymptomatically with “creeping” PAS formation to a higher degree than with pupil block conditioned glaucoma. Together with LCD values between 0.25 and 0.5, the risk of misdiagnosis in the form of latent POAG is therefore especially high in plateau iris conditioned glaucoma. This misdiagnosis can only be avoided through routine gonioscopy with the Posner lens in all glaucoma cases. It is important to stress that medical pressure reduction without miotics does not prevent continuing PAS formation. As in asymptomatic latent PAC glaucoma with pupil block, an asymptomatic case of latent PAC glaucoma with plateau iris can sometimes lead to subacute subjective symptoms in the form of slight blurring of vision and fleeting rainbow haloes with frontal headaches. This may thus mistakenly be perceived as representing a case of genuine acute glaucoma, maybe even pupil block conditioned! F In manifest PAC glaucoma (glaucoma angulo clauso manifestus) with plateau iris the angle is closed by PAS in > 80-90 degrees of the circumference, the untreated IOP (peak pressure) is permanently ≥ 24 mmHg, there are structural optic nerve and retinal changes and usually visual field defects (fig. 24). In connection with the typical asymptomatic manifest glaucoma there may sometimes be subacute subjective symptoms (blurring of vision and frontal headaches) in connection with pressure elevations as is the case in latent Argon-laser iridoplasty: Evaluation There are surprisingly few publications of the effect of iridoplasty with plateau iris.However, the application of argon-laser iridoplasty has increased throughout recent years and is now also recommended for acute PAC with pupil block when it is technically not possible to carry out YAG laser iridotomy26.

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Terminal manifest PAC glaucoma with plateau iris Referral diagnosis given by the patient’s ophthalmologist:

Not given.

A 66-year-old man with a history of 5 days of slight variation in visual acuity, especially in the right eye, with atypical colour phenomena. Goldmann applanation 38/40 mmHg untreated. Fairly deep chambers, bilateral LCD > 0.5 with clear media and deeply excavated optic discs. Treatment:

Diagnosis given by the local ophthalmological department:

Pilocarpine 4 % + betaxolol and 500 mg single dose acetazolamide and acute referral without specified glaucoma diagnosis.

Bilateral PAC glaucoma.

Bilateral LCD > 0.25, ACD 2.8/3.1 mm and occludable angle in 50 % of the circumference in both eyes. Goldmann applanation: 18/24 mmHg immediately following the treatment by the patient’s own ophthalmologist. Treatment 1:

Bilateral YAG-laser iridotomy and withdrawal of anti-glaucomatous treatment.

Following this, increasing IOP with varying treatment accentuation for one month at which stage it was observed that PAS had spread to the entire circumference in both eyes and the C/D ratio was found to be 0.8/0.9. Treatment 2:

Bilateral argon-laser iridoplasty due to suspect plateau conditioned PAC glaucoma.

Following iridoplasty in the right eye, signs of central vein thrombosis with decreasing central vision. After this, pressure increased in both eyes on sub-maximal and finally maximal medical treatment. In spite of this, on a diurnal curve a peak pressure of 29/24 mmHg was recorded at 7:15 p.m. (please note that at 8:15 a.m. and at 12:15 p.m. IOP on the left eye was only 14 and 15 mmHg, respectively). Subsequently, neovascular glaucoma developed in the right eye, and the patient was referred to the Glaucoma Clinic. Diagnosis given by the Glaucoma Clinic:

Terminal bilateral manifest PAC glaucoma with plateau iris. Manifest neovascular glaucoma right eye.

No light perception in the right eye, applanation 40 mmHg on treatment with pilocarpine, brimonidine, brinzolamide and acetazolamide. Oedematous cornea, iris rubeosis and PAS with neovascularisation reaching Schwalbe’s line involving the entire circumference. Central vein occlusion and C/D ratio 0.8 on ophthalmoscopy. In the left eye visual acuity was 6/9 + 3.25 sph. comb. – 0.75 cyl., LCD about 0.25, ACD 3.0 mm and on gonioscopy PAS in at least 80 % of the circumference and narrow occludable angle with flat iris and poor iris mobility in the area without synechiae. C/D ratio 0.9 with a corresponding tunnel vision of a few degrees. Diurnal curve on maximal treatment showed a peak pressure < 20 mmHg left eye, also at 7:15 p.m.! Treatment: Right eye pain treatment: Left eye maximal drug treatment:

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Comments Reason for unspecific treatment: 1. Neither the patient’s own ophthalmologist nor the referring eye department undertook a main- and subclassification of PAC since assessment of both iris mobility and PAS was omitted. No consequence was taken from the ACD measurement or the degree of C/D ratio. 2. A diurnal curve was not carried out until four months later at which stage normal IOP left eye was measured at 8:30 am and 12:15 pm (14 and 15 mmHg, respectively), however with an unacceptable pressure top in the evening (24 mmHg), i.e. not until this stage is it possible to adequately treat the terminal situation on the left eye. Outcome of unspecific treatment: 1. Laser treatment with a “trial and error” course instead of primary maximal drug treatment, which was not started until five months later!!!! 2. Additional IOP elevation after YAG-laser iridotomy and argon-laser iridoplasty because of terminal PAC glaucoma. 3. Neovascular glaucoma right eye.

In a prospective study from 1988 the effect of iridoplasty on imminent and chronic PAC as well as latent PAC glaucoma with plateau iris was evaluated on the basis of post-laser IOP and prone 25 dark-room test . The darkroom test was carried out without the pre-laser required pilocarpine treatment. The diagnostic and classification criteria were similar to those mentioned in this book. During an observation period of a minimum of six months without pilocarpine treatment, the dark-room test remained negative and untreated IOP was normal in 100% of all cases with imminent PAC. In chronic PAC pilocarpine was dispensable in 90% of all cases, whereas this was only the case in 55% of the cases with latent PAC glaucoma. The study thus demonstrates a sufficient effect of iridoplasty, however first and foremost in the early stages without PAS (imminent PAC) or PAS in < 50% of the angle circumference (chronic PAC). The necessary post-laser drug treatment in latent PAC glaucoma with plateau iris must therefore often include pilocarpine as opposed to the situation in latent PAC glaucoma with pupil block (see p. 62). When in doubt it is advisable to carry out a prone dark-room test. The long-term effect of iridoplasty in early plateau conditioned PAC with continued iris/cornea contact following iridotomy has 27 recently been reported by Ritch, Tham and Lam . Estimated on the basis of the clinical situation (IOP and gonioscopy) after six years in 23 eyes among 14 patients, the angle-opening laser-effect was still sufficient in 87% of the eyes after one iridoplasty treatment. Repeated treatment was necessary in the remaining three eyes

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after a few years. The examination thus indicates that the effect of iridoplasty is long-lasting in most eyes, but decreases in some cases with the indication for further treatment. Continued control (e.g. once a year) is therefore recommended after iridoplasty. This is the opposite of the case following YAG-laser iridotomy in early PAC with pupil block where the laser effect permanently excludes angle-closure (ref: YAG-laser iridotomy: Evaluation, p. 67). Post-laser complications are seen more frequently following iridoplasty than with YAG-laser iridotomy. In most cases, there is a minor intraocular reaction requiring local steroid treatment as well as the withdrawal of any pre-laser pilocarpine treatment. In many cases, a lesser degree of permanent pupil dilatation is seen, however only seldom does a laser-conditioned pressure increase occur in contrast to YAG-laser iridotomy. Extra powerful laser applications may lead to iris pigment hypertrophy around the laser burns. However, no serious complications such as cataract development or intra-ocular haemorrhages are seen. We therefore find there is a clear indication for iridoplasty with imminent PAC, acute/subacute PAC, chronic PAC as well as latent PAC glaucoma when the patient meets the diagnostic criteria as described above. In terminal manifest PAC glaucoma (C/D ratio 0.9 and/or tunnel vision), iridoplasty is not advised due to the risk of post-laser pressure increase (ref: Manifest PAC glaucoma with plateau iris). Argon-laser iridoplasty in general With respect to iridoplasty technique, one is referred to the section concerning treatment procedure, iridoplasty. It should, however, be stressed that it is advisable to determine the required energy amount (immediate visible iris shrinkage) in each individual patient by “titration”, always starting with a low energy position (100 mW). This is essential not only in order to avoid micro-explosions (bubble formation), but also because the required energy application is close to the pain threshold of many patients. Furthermore, the application of a lengthy exposure time (0.5 seconds) is often disturbing to the patients with respect to the required fixation. This is especially the case when indirect laser application via an angular mirror is used. Treatment is much easier to carry

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out for all parties involved when direct laser application on the iris root is performed using an Abraham iridotomy lens. This lens has an adequate and not too large a magnification when compared to the Wise iridotomy lens.

GROUP III: PAC MIXED GROUP (I+II) The occurrence of the grey transition cases found between the pure clinical entities is, as is well known, a challenge to the clinician. The main group III, which appears more frequently than the pure plateau cases, is a good example of this, as the pathoanatomy includes conditions of group I as well as group II. Here, a satisfactory course without unexpected treatment frustrations both for the ophthalmologist and for the patient can only be achieved when the patient has been correctly classified from the start. After this, the patient can be prepared for the possibility of a more complicated treatment course, including the application of both YAG-laser iridotomy and argon-laser iridoplasty. Again, the application of ACD is of decisive importance. As illustrated in fig. 18, main classification of PAC, gonioscopy shows varying degrees of both pupil block and plateau iris pathoanatomy. If the chamber angle anatomy is the only guideline used, it will often lead to incorrect placement into either group I or II. An ACD ≥ 2.1 mm and ≤ 2.4 mm may be used as a guideline since these ACD values lie between those found in typical cases of pupil block and the normal ACD values found with a pure plateau iris. Pathophysiolology and pathogenesis See the corresponding section under Group I: PAC with pupil block and Group II: PAC with plateau iris, respectively. Detection and diagnosis Detection is carried out by means of LCD, which is most often < 0.25 in this group. The actual diagnosis is made using “the mixed gonioscopy” findings together with ACD values between ≥ 2.1 mm and ≤ 2.4 mm.

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Subclassification with specific treatment and case reports As in the other main groups, the various development stages of the PAC mixed group require different forms of treatment. Therefore, a subclassification indicating the specific treatment regimes for each individual subgroup must be carried out. The terminology and definitions of the individual subgroups are the same as in I and II. The subdivision and the specific treatment are illustrated in fig. 25. SUBCLASSIFICATION

DEFINITIONS

A: Suspect PAC mixed group

A: Narrow occludable angle A: Control without in the upper sector, not in treatment the lower. No PAS

B: Imminent PAC mixed group

B: Occludable/appositional B: Iridotomy/iridoplasty? closed upper sector and (gonioscopy) occludable lower. No PAS. IOP < 24 mmHg

C: Acute/subacute PAC mixed group

C: Appositional angle closure involving 360 degrees. Temporary IOP ≥ 24 mmHg

C: Acetazolamide, pilocarpine, betablocker, alpha2-agonist, glycerol, iridotomy/ iridoplasty (gonioscopy)

D: Chronic PAC mixed group

D: PAS < 50% of the angle circumference. IOP < 24 mmHg

D: Iridotomy/iridoplasty? (gonioscopy)

E: Latent PAC glaucoma mixed group

E: > 50% PAS < 80-90% of the circumference. IOP permanently ≥ 24 mmHg. No structural or functional glaucoma defects

E: Iridotomy/iridoplasty? (gonioscopy) Postlaser drug treatment (pilocarpine?) Possibly cataract operation

F: Manifest PAC F: PAS > 80-90% + glaucoma mixed group structural optic nerve/ retina defects and/or visual field defects. IOP permanently ≥ 24 mmHg

SPECIFIC TREATMENT

F: Maximum drug treatment including pilocarpine/ (± iridotomy/iridoplasty)/ filtrating operation

Fig. 25. Subclassification of Group III: PAC mixed group II+II) and specific treatment.

A In suspect PAC (suspicio angulo clauso) mixed group the angle is narrow occludable in the upper sector, but not in the lower and with a varying degree of gonioscopic pupil block/plateau iris

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components. The axial chamber depth measurement shows values between those of the pure pupil block (I) and plateau iris (II) group (≥ 2.1 mm and ≤ 2.4 mm). Once the patient has been informed regarding glaucoma prodromal symptoms, control without treatment should be carried out every 6-12 months. B In imminent PAC (angulus clausus imminens) mixed group the angle is narrow occludable or appositional closed in the upper sector and occludable in the lower with a varying degree of gonioscopic pupil block/plateau iris anatomy as well as ACD ≥ 2.1 mm and ≤ 2.4 mm. There are no PAS in the chamber angle, normal untreated IOP and no structural nerve head/retinal changes or functional defects. The condition is thus asymptomatic and can only be detected by means of LCD < 0.25. Because of the pupil block component, the gonioscopic interpretation with respect to narrow occludable angle is usually easier than in the pure plateau iris situation. It is generally not necessary to carry out a supplementary dark-room test. The preventive, primary treatment is YAG-laser iridotomy. However, prior to the YAG-laser treatment the patient should be informed about a possible need for a subsequent iridoplasty. This is carried out if LCD does not change considerably and if the angle remains narrow occludable or appositional closed in the upper sector and ocludable in the lower. It should be emphasised that “post-YAG” gonioscopy with regard to the indication for argon-laser iridoplasty should preferably be carried out the day following the YAG-iridotomy in order to prevent a plateau iris conditioned acute PAC. A post-YAG elevation in IOP does not necessarily indicate the need for iridoplasty. The indication for this should solely be based on the gonioscopic pathoanatomy, especially noting the difference in the iris mobility between pupil block and plateau iris situations. Case report 6 is an example of this. If the eye pressure after YAG is normal, but the angle still seems to be narrow occludable with a plateau configuration, in case of doubt, a prone dark-room test should be performed to determine the necessity for an iridoplasty. Post-laser control is recommended after 1, 3 and 6 months and then annually.

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C The medical treatment of acute/subacute PAC (angulus clausus acutus/subacutus) mixed group is similar to that of the acute cases of pure pupil block or plateau iris (ref: Treatment procedures with PAC, p. 95). As mentioned earlier in acute PAC, the diagnosis should primarily be established by examining the healthy eye, which should then be treated preventively (pilocarpine and laser treatment). As soon as possible YAG-laser iridotomy of the acute eye is carried out with post-laser LCD and gonioscopic assessment with regard to indication for iridoplasty. This assessment should be carried out at the latest the day after YAG-laser treatment in order to avoid a new attack. In doubtful cases, a dark-room test should be carried out. Both the post-laser gonioscopy and the dark-room test should be undertaken on eyes not receiving any medications, especially pilocarpine. Post-laser control without drug treatment should be carried out after 1, 3 and 6 months and then annually. D As in the corresponding subgroups in main group I and II, asymptomatic “creeping” chronic PAC (angulus clausus chronicus) mixed group is probably more common than acute/subacute PAC, which is why the importance of detection by means of LCD should once again be stressed. As in I and II, the term chronic refers to the presence of permanent structural changes in the form of PAS, but in < 50% of the angle circumference, which is why the untreated IOP remains normal (fig. 25). As in B and C, the patient may prior to treatment be informed that the treatment will probably be curative, but may possibly require the application of both YAG-laser and argon-laser therapy. As mentioned in C, this decision should be made the day following YAG-laser iridotomy in an untreated eye. As appears from case report 7, omission of this may lead to a frustrating and lengthy treatment course. Finally, post-laser control without drug treatment is recommended after 1, 3 and 6 months and then annually.

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Case report 6

Imminent PAC mixed group with pupil block dominance Referral diagnosis given by the patient’s ophthalmologist:

Narrow-angle glaucoma – bilateral plateau iris.

A 55-year-old woman with a one year history of attacks of blurred vision and headaches. Treatment:

Bilateral YAG iridotomies (by the patient’s local ophthalmologist).

Continued prodromal attacks in the right eye in spite of YAG iridotomy. The iridotomy was described as being smaller in the right eye as compared to the left. ACD 2.2 mm bilaterally. After laser treatment gonioscopy revealed a narrow occludable angle with poor iris mobility in the periphery, especially on the right side. The patient was then treated with pilocarpine 2 % in both eyes, which resulted in a considerably discomforting miosis. The patient was then referred to the Glaucoma Clinic for iridoplasty. Diagnosis given by the Glaucoma Clinic:

Imminent PAC mixed group with pupil block dominance.

LCD right eye < 0.25 with localised iris/cornea contact, LCD left eye > 0.25, ACD 2.2/2.3 mm. In the right eye, there was a narrow occludable angle without PAS and with an anterior convex iris with pronounced iris mobility and only a suggestion of an iris knee. In the left eye, there was an open, non-occludable, angle without PAS and with a slight anterior convex iris. The right eye showed a small iridotomy < 100 microns without any opening through the pigment epithelium. Contrary, there was a large completely penetrating iridotomy on the left side. IOP was 16 mmHg bilaterally on pilocarpine treatment. Ophthalmoscopy revealed a bilateral C/D ratio of 0.2 without structural changes. Visual fields on automatic perimetry were normal. Treatment:

YAG-laser dilatation of iridotomy right eye.

Following this, LCD > 0.25 right eye and normal pressure without treatment with a negative dark-room test. Comments Reason for unspecific treatment: 1. The referring ophthalmologist failed to assess the functional effect of the iridotomy in the right eye by means of LCD assessment immediately following laser treatment. 2. The referring ophthalmologist did not determine whether there was an adequate opening through the pigment epithelium in the right eye after the YAG-laser treatment by using retro-illumination and did not assess the adequacy of the stromal size of the hole of the iridotomy by means of the 0.2 mm “spot” from Haag-Streit slit lamp or the 100 micron “spot” from an argon laser (ref: YAG-laser iridotomy in general, p. 59). 3. The referring ophthalmologist misinterpreted the gonioscopy as representing a plateau iris. The anterior convex iris contour was not observed, and assessment of mobility was confined to that of the iris root instead of the iris contour in its entirety. Outcome of unspecific treatment: 1. Patient frustration due to length of the treatment course without the anticipated laser effect. 2. Discomfort due to the miosis.

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E In latent PAC glaucoma (glaucoma angulo clauso latens) mixed group IOP is permanently ≥ 24 mmHg due to PAS in > 50% – < 80-90% of the angle circumference, but there are no structural glaucoma changes in the posterior part of the eye, and there are no functional defects. Even following sufficient laser treatment, permanent pressure reducing drug treatment is therefore necessary in order to prevent the development of manifest PAC glaucoma. As in I and II, an asymptomatic “creeping” PAC glaucoma may sometimes lead to brief subjective symptoms in the form of rainbow haloes and blurred vision. As mentioned in III B, C and D, post-YAG laser assessment (gonioscopy and LCD) should be carried out as soon as possible after iridotomy with regard to performing iridoplasty in order to avoid plateau iris conditioned acute angle closure. In all cases it is important to assess whether the drug treatment is adequate (diurnal curve). In plateau iris dominance requiring iridoplasty, the required drug treatment often includes pilocarpine as mentioned in II E (p. 80). In case of doubt, a prone dark-room test on drug treatment excluding pilocarpine may be carried out. F As in the corresponding groups under I and II, structural changes to the optic nerve head and in the retinal nerve fibre layer with associated visual field defects are found in manifest PAC glaucoma (glaucoma angulo clauso) mixed group. The pressure is permanently increased (≥ 24 mmHg) due to PAS in more than 80-90 degrees of the angle circumference. When identification of PAS in 360 degrees of the circumference can be verified with a reasonable degree of certainty, a pressure reducing effect of YAG-laser iridotomy/argon-laser iridoplasty or indeed cataract operation is not to be expected. In such a situation, maximum drug treatment (three different medications at most) is prescribed, naturally including pilocarpine. This decision is supported by diagnosing the presence of severe structural changes (C/D ratio: 0.8 or 0.9) and/or extensive functional defects. In case of suspect terminal PAC glaucoma an adequate ophthalmoscopy, if necessary after pupil dilation with metaoxedrine 2,5% drops, and a subsequent automatic perimetry is therefore recommended

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Case report 7

Chronic PAC mixed group with plateau iris dominance (see fig. 23, UBM from this patient) Referral diagnosis given by the patient’s ophthalmologist:

Bilateral latent angle-closure glaucoma – plateau iris. Bilateral hypermetropia (+4.5 D/+4.0D).

A 44-year-old nurse with a history of 5-10 attacks of blurred vision and rainbow haloes in both eyes every year for the last four years. A severe attack with nausea, blurred vision and rainbow haloes four weeks prior to ophthalmic consultation. Diagnosis given by the referring ophthalmological department: 1. Bilateral intermittent primary angle-closure glaucoma. Bilateral LCD < 0.25, ACD 2.0/2.2 mm, gonioscopy showed narrow occludable angles with PAS in the upper sector in both eyes, Goldmann applanation: 20/18 mmHg on treatment with pilocarpine 4 % (local ophthalmologist) and normal optic discs without structural changes. Treatment:

Bilateral YAG-laser iridotomy.

Discharged to the local ophthalmologist the day following therapy, but without gonioscopy and without treatment as the patient is informed that “the problem is most likely solved”. 2. Plateau iris glaucoma Again referred by the local ophthalmologist after two weeks following an attack with rainbow haloes in the right eye. Goldmann applanation 16 mmHg in both eyes on treatment with pilocarpine. Treatment:

YAG-laser dilatation of former iridotomy in the right eye owing to a few stromal fibrillae. Due to a suspicion of a subclinical attack: Dark-room test without pilocarpine (19/18 mmHg → 57/34 mmHg + rainbow haloes). Treatment: Pilocarpine 2 % x 2 both eyes. After this dark-room test: Pilocarpine treatment for six months with considerable miosis discomfort (blurred vision a few hours after pilocarpine. The patient managed by not wearing glasses after the pilocarpine application). Due to the discomfort referral to the glaucoma clinic. Diagnosis given by the Glaucoma Clinic:

Bilateral chronic PAC mixed group with plateau iris dominance. Bilateral LCD = 0.25, ACD 2.2/2.3 mm, large iridotomies and narrow, occludable angles with plateau iris configuration and little iris mobility on gonioscopy. PAS 10-3 o’clock in the right eye, 12-3 o’clock in the left eye as is illustrated in fig. 23 (UBM from the patient), bilateral C/D ratio 0.2 without structural changes and normal visual fields on automatic perimetry. Treatment:

Iridoplasty x 2 on both eyes.

After this, dark-room test without pilocarpine was negative (17/15 → 19/17 mmHg). The course was then satisfactory with IOP < 20 mmHg without treatment with an observation time of four years. Due to suspicion of continuing PAS development, renewed bilateral iridoplasty after three years.

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Main groups and subclassification of PAC 91 Comments Reason for unspecific treatment: 1. Lack of pre-laser main classification of PAC owing to insufficient gonioscopy (no plateau iris configuration or iris mobility assessment with the Posner lens) and lack of interpretation of the ACD measurement. 2. Consequently, the required gonioscopy immediately after YAG-laser iridotomy was not carried out. 3. No application of argon-laser iridoplasty. Outcome of unspecific treatment: 1. Patient frustration due to renewed referral with recurring glaucoma attack in spite of “curative” YAG-laser iridotomy. 2. Visual problems caused by pilocarpine treatment.

before treatment. Case report 8 is an example of unspecific treatment of manifest PAC glaucoma due to inadequate gonioscopy and insufficient assessment of structural/functional defects and illustrates the consequences that ensued. If in doubt as to the stage of development of PAC, an iridotomy possibly followed by iridoplasty can be performed, but this may lead to post-laser pressure increases, especially in advanced glaucoma. In terminal manifest PAC glaucoma (C/D ratio 0.9 and/or tunnel vision) YAG-laser iridotomy and argon-laser iridoplasty are therefore generally contraindicated. If maximum drug treatment is not accepted or when a diurnal curve shows a peak pressure of > 20 mmHg, a filtrating operation should be carried out, possibly a combined cataract trabeculectomy procedure (ref: Treatment procedures: Fistulating operation, p. 108). YAG-laser iridotomy/argon-laser iridoplasty: Evaluation The indication for YAG-laser iridotomy and argon-laser iridoplasty in the mixed group is the same as described in the section concerning iridotomy evaluation under I. PAC with pupil block (p. 67) and the section concerning iridoplasty evaluation under II. PAC with plateau iris (p. 80). As mentioned above, these laser indications also apply to imminent PAC in the mixed group. The advantage of the correct classification of an eye into the mixed group is that it not only creates the possibility for proper planning of treatment, but also allows realistic patient information to be given with regard to the expected treatment course. With regard to subsequent iridoplasty, the indication for this should be estab-

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Case report 8

Manifest PAC glaucoma mixed group with pupil block dominance Referral diagnosis given by the patient’s ophthalmologist:

Acute glaucoma right eye.

A 47-year-old woman with a history of attacks of rainbow haloes and frontal headaches for a period of six months treated as migraine by the general practitioner. Referred by the local ophthalmologist because of Goldmann applanation pressures 60/20 mmHg. No further information available. Treatment: None. Diagnosis 1 given by the local ophthalmological department:

Acute angle-closure glaucoma right eye and latent glaucoma left eye.

Goldmann applanation 60/20 mmHg untreated. LCD < 0.25. Gonioscopy after medical treatment: Narrow occludable angles without PAS, suspect plateau iris. Normal optic nerve heads without loss of tissue in both eyes. Treatment: Bilateral YAG-laser iridotomy. Discharged to the local ophthalmologist without further treatment. Acute re-referral from local ophthalmologist after five days with rainbow haloes and frontal headaches and Goldmann applanation pressure 32 mmHg in the right eye. Diagnosis 2 given by the ophthalmological department: Treatment: Following this, referral to the Glaucoma Clinic.

Bilateral chronic angle-closure glaucoma. Dorzolamide both eyes and brimonidine right eye.

Diagnosis given by the Glaucoma Clinic:

Manifest PAC glaucoma right eye, latent PAC glaucoma left eye, mixed group with pupil block dominance. Goldmann applanation at 2 pm: 15 mmHg bilaterally on treatment with dorzolamide both eyes and brimonidine right eye. LCD < 0.25 in the right eye, > 0.25 in the left eye. ACD 2.3/2.4. PAS in the right eye except between 5 and 6 oćlock where there was pigment dispersion in the angle, in the left eye PAS in the upper and the nasal sectors, i.e. > 50 %. Increased iris mobility without iris knee using Posner indentation in the rest of the circumference. In the right eye, C/D ratio 0.7 with structural changes in the optic disc and retina corresponding to a small nasal defect found on automatic perimetry. In the left eye, C/D ratio 0.4 without structural changes corresponding to a normal automatic perimetry. Diurnal curve on dorzolamide both eyes, and brimonidine right eye showed a peak IOP of 29/20 mmHg, however only at 8.15 am, with IOP < 20 mmHg at 3.15 pm!! Treatment:

Right eye: Maximum drug treatment (combined pilocarpine-timolol, brimonidine, brinzolamide). Left eye: Brimonidine.

After this, IOP < 20 mmHg in both eyes (diurnal curve)

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Main groups and subclassification of PAC 93 Comments Reason for unspecific treatment: 1. The local ophthalmological department did not carry out an ACD measurement or establish a PAS diagnosis owing to inadequate gonioscopy (Posner indentation was not performed). 2. Incorrect optic nerve head assessment (normal discs). Incorrect suspicion of plateau iris, because iris motility was not assessed. 3. No final diurnal curve was performed with regard to adequacy of treatment. Outcome of unspecific treatment: 1. The patient was discharged from the ophthalmological department without drug treatment after YAG-laser iridotomy. This led to a new acute referral. 2. This new acute referral led to unspecific submaximal drug treatment instead of optimal treatment due to inadequate PAC subclassification in the right eye.

lished as soon as possible after performing iridotomy, i.e. preferably on the following day by means of gonioscopy without the use of pilocarpine and under minimum illumination (both lighting in the room and slit lamp). In case of doubt a prone dark-room test is recommended. YAG-laser iridotomy/argon-laser iridoplasty in general See the same section under groups I and II (p. 69 and 83).

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Treatment procedures with PAC 95

TREATMENT PROCEDURES WITH PAC

By John Thygesen

PRINCIPLES OF TREATMENT WITH ACUTE PAC I, II AND III • Examine both eyes and make note of both peripheral and central chamber depths (LCD and ACD), the contour of the iris as well as the findings on indentation gonioscopy. Should corneal oedema preclude adequate examination of the acute eye, base the initial PAC diagnosis on the examination of the fellow eye. • Lower intraocular pressure using drugs that reduce the production of aqueous fluid: Carbonic anhydrase inhibitors, beta-blockers and alfa2-agonists. • Repeat the ophthalmological examination after 1/2-1 hour. The IOP will typically be reduced, but the angle will remain appositionally closed. At a tension < 50 mmHg the pressure conditioned ischaemia will typically have subsided and the pupillary sphincter therefore be sensitive to pilocarpine medication. One drop of pilocarpine 2% should then be administered and assessment repeated after a further 15-30 minutes. If necessary repeat the pilocarpine treatment 3-4 times during the following hour. • If after the first 1/2-1 hour the pressure remains > 50 mmHg, oral hyperosmotic agents such as glycerol or intravenous mannitol (cave diabetes, pulmonary oedema) may be added followed by pilocarpine. • Procedure in connection with hyperosmotic agents: Place the patient in a supine position. This allows the lens to gradually fall back into position as the volume of the vitreous body becomes reduced by the hyperosmotic agents used. This reduction comprises only about 3% of the total vitreous volume, but this is equivalent to 0.12 cc or twice the volume of the posterior chamber or half of the volume of the anterior chamber. • If the pressure is thereby reduced and a repeated gonioscopy in the acute eye (typically after applying 50% glucose in order to remove any remaining corneal oedema) shows a narrow occlud-

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able angle without PAS, pilocarpine 2% x 4 daily is prescribed together with local steroids until the inflammation has been further reduced. • Based on gonioscopy (ref: 1. Iris contour and iris mobility, p. 33) together with ACD measurement the case in question is classified under I, II or III (ref: Main classification of PAC, p. 50), whereas the subclassification with the attached final specific treatment are based on the presence of any PAS, any structural optic disc changes, and/or functional defects (ref: Subclassification with specific treatment, PAC groups I, II and III, p.58, 75 and 85). • As mentioned under latent and manifest PAC glaucoma groups I, II and III, an asymptomatic “creeping” chronic PAC may sometimes become converted into a subacute/acute condition, i.e. behind a seemingly acute PAC, a chronic condition in the need of post-laser medical therapy or even a fistulating operation may be hidden. Therefore, as repeatedly mentioned in the foregoing chapters, a thorough initial examination before starting any treatment is of vital importance in order to avoid unspecific treatment (“trial and error” method). N.B.! The axiom to date in angle-closure glaucoma has been to use extensive amounts of pilocarpine. However, this is only very seldom necessary. Should excess therapy with pilocarpine 4% be applied, a rise in pressure due to an increased pupil block may sometimes paradoxically occur and gastrointestinal side effects may present. TREATMENT OF ACUTE PAC I, II AND III (PREVIOUSLY “ACUTE GLAUCOMA”) I. Preliminary treatment 1. Reduction of aqueous fluid production Acetazolamide (Diamox®) 10 mg/kg intravenously (cave sulphonamide allergy) (N.B.! Topical CAIs such as dorzolamide (Trusopt®) or brinzolamide (Azopt®) are not recommended as they have a reduced IOP lowering effect in the presence of corneal oedema). Local alpha -agonist (e.g.: Iopidine®, Alphagan®). 2 Local betablockers (cave asthma).

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2. Elimination of iris/cornea apposition (restitution of outflow) Corneal indentation with a hand-held Goldmann tonometer head. Aqueous fluid in the anterior chamber is thereby pressed into the chamber angle, which may then be opened in certain cases. 3. Pupil constriction Pilocarpine eye drops 2% x 1, 1/2-1 hour after performing points 1 and 2 as IOP is then generally < 50 mmHg, i.e. the pupillary sphincter is again pilocarpine sensitive due to the elimination of the pressure conditioned ischaemia. The pilocarpine 2% medication is repeated 3-4 times during the following hour. (Stronger miotics such as pilocarpine 4% or more frequent doses may sometimes increase the pupil block and lead to a so-called paradoxical pressure increase.) 4. Inflammatory treatment Local corticosteroid, e.g. dexamethasone x 4 daily.

II. FOLLOW-UP TREATMENT AFTER 1-2 HOURS A. If the attack is interrupted: Pressure reduced. Pupil contracted. Corneal oedema reduced. 1. Classification Repeat the gonioscopy and possibly the ACD with regard to a final classification into main groups and subgroups with regard to the specific treatment of the case in question. 2. Pupil constriction Prescribe pilocarpine eye drops 2% x 4 daily for both eyes. In the presence of extensive PAS possibly combined with structural optic disc changes further drug treatment should be administered as mentioned in the chapters: Subclassification and specific treatment of PAC I, II and III (p. 58, 75 and 85). 3. Inflammatory treatment Local corticosteroid, e.g. dexamethasone x 4 daily. 4. YAG-iridotomy and argon-laser iridoplasty An iridotomy should be arranged for in both eyes in acute PAC with pupil block (I) and in the mixed group (III) when the pupil block appears to be the dominating factor (ref: Acute PAC, group I,

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p. 59 and III, p. 87). In acute PAC with plateau iris, arrange for a primary iridoplasty (ref: II: Acute PAC with plateau iris, p. 77). Should the final classification indicate subacute/acute attack in a previous asympomatic, chronic course, the specific treatment of the case concerned is planned as illustrated in the chapters: Subclassification with specific treatment of PAC groups I, II and III. YAG-laser iridotomy and argon-laser iridoplasty: Generally, preventive iridotomy should first be performed in the healthy eye. Iridotomy in the acute eye should not be carried out until the cornea has cleared and the intraocular inflammation has been sufficiently reduced (iris without hyperaemia). In the case of uncertain gonioscopic subclassification it is important to note that a reduced IOP in the days immediately following acute PAC may be caused by a reduced aqueous production due to pressure-conditioned ciliary body ischaemia. In other words, the pressure reduction itself cannot alone account for any opening of the chamber angle. In such cases, observation on the above-mentioned medication will clarify the situation making it possible to avoid unspecific treatment. Generally, however, iridotomy should be carried out as soon as technically possible in order to utilize the synecholysis effect of the treatment on any new PAS formations. Adequate gonioscopic evaluation should therefore be carried out as early as possible in the course of the disease process with regard to the optimal planning of the specific treatment. In iridoplasty in acute PAC with plateau iris (II) the same considerations as mentioned above are applicable. It is to be noted that direct argon-laser iridoplasty using an Abraham lens (really designed for iridotomy) can adequately be carried out in the presence of a slightly cloudy cornea, i.e. earlier than iridotomy (see below). B: If the attack is not interrupted: Pressure continuously high. Pupil dilated. Cornea oedematous. 1. Osmotic reduction of the vitreous volume Oral Glycerol 1.0-1.5 g/kg (cave diabetes) or intravenous 20% Mannitol (1.0-1.5 g/kg) over 30 minutes.

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2. Supine position for one hour In this manner the lens will gradually move posteriorly as mentioned above. 3. If the patient is in pain: Systematic analgesics. 4. If the patient feels nauseous or is vomiting: Intramuscular metoclopramide. C: If the attack is then interrupted 1. Continue pilocarpine eye drops 2% x 4 daily. 2. Continue corticosteroid eye drops x 4 daily. 3. Plan specific treatment as mentioned under A. D: If the attack is not successfully interrupted, i.e. IOP > approx. 30 mmHg With a clear cornea: Repeated gonioscopy with regard to final subclassification as a continued increased IOP in spite of clear cornea generally implies PAC glaucoma in group I, II or III. Following this, specific treatment is planned as illustrated in fig. 19, p. 52: Flow chart for specific treatment of PAC. In the presence of visually impairing cataract, phaco-extraction may improve the outflow possibilities in latent PAC glaucoma. An improved outflow should not of course be expected in manifest PAC glaucoma where PAS involves almost the entire circumference (> 80-90%), indeed in this situation there is a risk of a post-operative increase in pressure. In such a case a combined cataract and glaucoma operation should therefore be considered (ref: Fistulating operation). With continued cornea oedema: If it is not possible to carry out adequate gonioscopic subclassification and YAG-laser iridotomy, and when the patient history indicates a short-term acute course, argon-laser iridoplasty should be attempted even though examination of the healthy eye suggests that the case belongs to groups I, or III.

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With continued extreme cornea oedema: If it is not technically possible to perform an iridoplasty, the case is treated as in manifest PAC glaucoma (ref: Flow chart, fig. 19, p. 52).If maximum drug treatment including pilocarpine does not lead to IOP ≤ 20 mmHg, or if the patient is unable to accept the treatment, a fistulating operation should be performed. As the situation is often caused by PAS in the entire angle circumference, a cataract extraction will naturally not improve the outflow situation.

YAG-LASER IRIDOTOMY YAG-laser iridotomy eliminates the pressure difference between the anterior and posterior chambers caused by the abnormal pupil block and thereby flattens the iris. In this way, the chamber angle is opened provided there are no PAS present (see also: Pathophysiology and pathogenesis, Group I: PAC with pupil block, p. 53). Indications • • • •

Imminent PAC with pupil block groups I and III Acute/subacute PAC with pupil block groups I and III Chronic PAC with pupil block groups I and III Latent PAC glaucoma with pupil block groups I and III (In manifest PAC glaucoma with pupil block (I) and mixed group (III) where PAS are present in > 80-90% of the angle circumference iridotomy will not have a pressure reducing effect, possibly even the opposite) Concerning YAG-laser indications and necessary post-laser anti-glaucomatous drug treatment see also: Subclassification with specific treatment of PAC with pupil block group I, p. 58) and group III (p. 85) as well as fig. 19 (p. 52): Flow chart for specific treatment of PAC

Contraindications • Terminal manifest PAC glaucoma (C/D ratio 0.9 and/or tunnel vision) with pupil block groups I and III due to the risk of post-laser increase in pressure

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• Extremely flat anterior chamber with iris/cornea contact as is for instance found in nanophthalmos (ref: Pathophysiology and pathogenesis, PAC with pupil block, p. 55). Under such circumstances iridotomy may result in ciliary block or uveal effusion (formerly known as malignant glaucoma). The alternative laser treatment is iridoplasty • Pronounced corneal oedema • Anticoagulation therapy and acetylsalicylic acid treatment: The treatment should be interrupted for a few weeks prior to laser application Technique26 • Local anaesthesia • Apraclonidine (Iopidine®) pre-laser: Reduces post-laser pressure increase and bleeding • 2% pilocarpine x 1 pre-operatively in order to achieve miosis and thus an extension of the iris tissue (easier laser perforation) and an improved possibility for creating a peripheral iridotomy, which will be covered by upper eyelid (no dazzle) • Lens: Wise laser-iridotomy lens (ocular + 103 D) • Laser burns: Energy: Start with 1.5 – 3.0 mJ.Adjust for iris colour. Energy in brown iris > blue iris. In brown iris: Defocus posteriorly towards the iris pigment layer (“volcano effect” with maximum energy absorption in the pigment layer). Preferably no more than five applications Choose an iris crypt peripherally in the upper area where the patient’s eyelid will provide cover (fig. 26). In this manner, dazzle and lens damage may as mentioned be avoided. Register the functional iridotomy effect by observing the change in LCD. If there is no change in the limbal chamber depth: Assess whether the iridotomy has penetrated all iris tissue and whether it is large enough (ref: YAG-laser iridotomy in general, p. 69). Possibly repeat the gonioscopy with regard to reviewing the classification (PAS?).

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Fig. 26. Combined YAG-laser iridotomy/argon-laser iridoplasty in a patient with imminent PAC III, mixed group with plateau iris dominance. Svend V. Kessing, the Glaucoma Clinic, Copenhagen University Hospital.

• Post-treatment: Local steroid x 3-4 daily for 3-5 days • Control: Pressure measurement after 1-3 days. Especially in cases with PAC mixed group (group III), gonioscopy should be repeated the following day with regard to possible plateau iris with continued occludable angle representing an indication for iridoplasty • Complications: Haemorrhage from iris. IOP increase (within 3 hours post-laser). Minor iritis and posterior synechiae. Closure of iridotomy. Lens damage? Corneal laser marks See also: YAG-laser iridotomy: Evaluation (p. 67).

ARGON-LASER IRIDOPLASTY In argon-laser iridoplasty8 laser energy is applied centrally to the pathological prominent iris knee (ref: Normal anatomy of

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the chamber angle, 1. Iris contour and iris mobility (p. 33) and pathophysiology and pathogenesis, group II, PAC with plateau iris, p. 71). The heat generated causes shrinkage of the iris tissue, thus opening the narrow chamber angle (fig. 27). In group II: PAC with plateau iris where the pathogenesis is purely plateau conditioned without any pupil block component, iridoplasty represents the specific treatment since YAG-iridotomy does not have any effect whatsoever in this situation (see case report 4, p. 79).

Fig. 27. Argon-laser iridoplasty in plateau conditioned PAC.

Indications • Imminent (threatening) PAC with plateau iris (group II) and imminent PAC mixed group (group III) in cases where YAG-laser iridotomy in group III has not opened the chamber angle. • Subacute/acute PAC with plateau iris (group II) and subacute/ acute PAC mixed group (group III) in cases where YAG-laser iridotomy in group III has not opened the chamber angle. • Chronic PAC with plateau iris (group II) and chronic PAC mixed group (group III) in cases where YAG-laser iridotomy in group III has not opened the chamber angle. • Latent PAC glaucoma with plateau iris (group II) and latent PAC glaucoma, mixed group (group III) in cases where YAGlaser iridotomy has not opened the chamber angle. • (In manifest PAC glaucoma with plateau iris (group II) or mixed group (group III) with PAS in > 80-90% of the angle circum-

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ference iridoplasty most often will have no pressure reducing effect, possibly even the opposite.) • With regard to iridoplasty indications and possible post-laser anti-glaucomatous drug treatment see also: Subclassification with specific treatment, groups II and III (p. 75 and 85) and fig. 19: Flow chart for specific treatment (p. 52). Relative iridoplasty indications • Subacute/acute PAC with pupil block where acute anti-glaucomatous drug treatment is ineffective and where there is no possibility of obtaining a sufficient YAG-laser iridotomy owing to cornea oedema • Secondary angle-closure (SAC) due to a subluxated lens (forward-axial) and in hypermature cataract with increasing lens thickness where the YAG iridotomy is inadequate • Nanophthalmos (ref: Group I: Pathophysiology and pathogenesis, p. 56) as an alternative to YAG-laser iridotomy Contraindications • Pronounced corneal oedema (may lead to corneal burns in both endothelium and stroma) • Flat anterior chamber with extensive iridocorneal contact (in some cases laser treatment may be initiated intermedially on the iris and then followed up by placing the burns in a more peripheral fashion resulting in successive peripheral angle opening, e.g. in nanophthalmos) • Terminal manifest PAC glaucoma (C/D ratio 0.9 and/or tunnel vision). Technique • Local anaesthesia • Apraclonidine (Iopidine®) pre-operatively • 2% pilocarpine x 1 pre-operatively in order to pull the iris knee as centrally as possible (should not be used following iridoplasty) • Laser wavelength: Blue-green • Lens: Abraham iridotomy lens (ocular + 66 D), which provides a suitable enlargement whereas the Wise iridotomy lens (ocu-

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•

• •

•

lar + 103 D) provides an enlargement, which is excessive and therefore impractical (see also: Argon-laser iridoplasty in general, group II, p. 83) Laser burns: *24 burns placed over 360 degrees with approx. 2 “spot” diameters between each burn (fig. 26 and 27). Focus peripherally on the iris (on the iris knee). *“Spot” diameter: 200–500 microns *Time: 0.5 seconds *Laser energy: 100-400 mW depending on iris colour Highest energy in lesser pigmented irises. Determine the required energy amount (immediate visible iris shrinkage) in each individual patient by “titration”, always starting with a low energy position (100 mW). In case of bubble formation: Reduce the energy Post-treatment: Local steroids x 3-4 daily for 3-5 days Control: Gonioscopy immediately post-laser and then at least annually in order to assess any degree of angle closure requiring further iridoplasty treatment (Ref: Group II, Argon-laser iridoplasty: Evaluation p.69.) Complications: Minor iritis. Larger pupil. Iris pigment hypertrophy from the laser burns. Rarely increase in IOP

FISTULATING OPERATION By Svend V. Kessing It is not the aim of this book to give a detailed account of the trabeculectomy procedure as such. However, indications and postoperative treatment will be mentioned together with a brief description of the post-operative complications, which are especially found to occur in PAC with pupil block. Finally, suggestions for preventive measures in connection with these complications will be put forward.

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Indication Primarily in manifest PAC glaucoma with pupil block (group I), with plateau iris (group II) and mixed group (group III) when maximum anti-glaucomatous medication is ineffective (ref: Subclassification with specific treatment of PAC I, II and III, p. 58, 75 and 85; and fig. 19, p. 52: Flow chart for specific treatment). In the case of terminal manifest PAC glaucoma in an only eye, transscleral diode laser cyclophotocoagulation should be considered instead of trabeculectomy due to the complications which can occur in fistulating operations as mentioned below. Complications 1. Post-operative hyperfistulation Due to the particular pathoanatomy found in eyes with PAC with pupil block (ref: Pathophysiology and pathogenesis, group I PAC with pupil block, p. 55), there is a pronounced tendency for postoperative hyperfistulation to occur as compared to eyes with primary open-angle glaucoma. This leads to hypotension with various degrees of anterior chamber flattening. 2. Choroidal detachment Hypotension often leads to choroidal detachment with further hypotension due to the cessation in aqueous production that follows. This will result in a closure of the filtrating bleb (subconjunctival fibrosis) and an increased IOP when aqueous production is re-established, i.e. indication for re-operation. 3. Ciliary block (formerly known as malignant glaucoma) This complication is almost only found in manifest PAC glaucoma since it is only very seldom seen in either primary or secondary open-angle glaucoma. As is well-recognised, this is a most serious complication that requires urgent acute operative intervention with “vitreous tap” (removal of intravitreal aqueous pockets), most easily done via an opened trabeculectomy, which is subsequently closed in a more solid fashion. In the situation with a large iridectomy YAG laser photo-disruption of a visible hyaloid membrane could be attempted before performing a “vitreous tap”.

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Prevention of post-operative hyperfistulation The above-mentioned hyperfistulation is prevented by using 6 tight 10-0 nylon sutures in the scleral flap where the two most limbal sutures are placed as so-called disposable sutures, i.e. sutures where the knots are situated in the cornea enabling them to be removed without any risk of external fistulation. This procedure is preferred to post-operative transconjunctival laser-burning of the sutures, which in fact is often quite impossible to perform due to conjunctival oedema and haemorrhage. This suture technique is especially necessary when using 5-FU or Mitomycin C for anti-fibrotic treatment as these treatment procedures alone involve a high risk of hyperfistulation. In this connection, it should be emphasised that a combined cataract and glaucoma operation requires anti-fibrotic treatment in order to ensure continued fistulation. In a combined operation separate procedures are therefore recommended with a corneal phacoextraction and a separate trabeculectomy with Mitomycin C (0.2 mg/ml for 3 minutes) in the upper area of the eye. In cases of terminal PAC glaucoma, trabeculectomy alone is recommended followed by phacoextraction through a corneal incision as combined operations have higher post-operative pressure levels than a solitary trabeculectomy. Post-operative treatment 1. Scopolamine eye drops x 3 daily for as long as hypotension (IOP < 5 mmHg) and a tendency towards flat anterior chamber exist. 2. Steroid eye drops, e.g. dexamethasone x 4 daily, individualised (> 5 weeks) until a non-hyperaemic, diffuse fistulation bleb is found (i.e. no sign of active subconjunctival fibrosis). 3. Cutting of disposable sutures (anteriorly placed scleral flap sutures as mentioned above) when IOP is > 15 mmHg. With adequately tightened scleral flap sutures in cases without antifibrotic treatment (5 FU or Mitomycin C) it is generally advisable to cut the disposable sutures on the second or third post-operative

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day. When anti-fibrotic treatment has been used, suture cutting should be left until at least one month post-operatively. 4. Bulbar massage to create “hydro-dissection” of incipient subconjunctival fibrosis (in cystic blebs). Bulbar massage is carried out under slit lamp control using gentle and continuous pressure at the outer angle of the eyelid with the index finger, thereby compressing the bulbus against the nasal orbital wall. At the same time, the bleb is observed through the slit lamp enabling finger pressure to be adjusted according to changes in the bleb appearance. With a high bleb configuration without any spreading to the conjunctiva on the sides bleb compression is carried out transpalpebrally (“bleb modulation”) in order to hydro-dissect any tendency to subconjunctival fibrosis until the bleb has become more diffuse. It should be emphasised that the primary purpose of bulbus massage is to eliminate incipient subconjunctival fibrosis and not to reduce the eye pressure. Bulbus massage should therefore be carried out as soon as IOP > approx. 10 mmHg and not left until the pressure has become increased (> 20 mmHg) as the fibrosis will generally be irreversible at this stage.

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References 109

REFERENCES 1.

2. 3. 4. 5. 6. 7. 8. 9. 10.

11.

12. 13. 14. 15. 16. 17. 18.

19.

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Van Herick W, Shaffer RN and Schwartz A. Estimation of the width of the angle of anterior chambers: Incidense and significance of the narrow angle. Am J Ophthalmol 1969;68:626-629. Ascher KW. Partial coloboma of the scleral-limbus zone with visible Schlemm’s canal. Am J Ophthalmol 1941;24:615-19. Törnquist R. Chamber depth in primary acute glaucoma. Br J Ophthalmol 1956;40:421-29. Scheie HG. Width and pigmentation of the angle of the anterior chamber. Arch Ophthalmol 1957;58:510-12. Shaffer RN. Gonioscopy, ophthalmoscopy and perimetri. Trans Am Acad Ophthalmol Otolaryngol 1960;64:112-25. Spaeth GL. The normal development of the human anterior chamber angle: a new system of descriptive grading. Trans Ophthalmol Soc 1971;91:709-39. Ritch R. Plateau iris is caused by abnormally positioned ciliary processes. J Glaucoma 1992;1:23-26. Ritch R Jeffrey M and Liebmann M. Argon laser peripheral iridoplasty. Ophthalmic Surg and Lasers 1996;27:289-99. Barkan O. Glaucoma: Classification, causes and surgical control. Am J Ophthalmol 1938;21:1099-1105. Rosengren B. Studien uber die tiefe der vorderen augenkammer mit besonderer hinsicht aus ihr verhalten beim primären glaukom I. Acta Ophthalmol 1930;8:99-136. Rosengren B. Studien uber die tiefe der vorderen augenkammer mit besonderer hinsicht aus ihr verhalten beim primären glaucoma II. Acta Ophthalmol 1931;9:121-42. Törnquist R. Angle-closure glaucoma in an eye with a plateau type of iris. Acta Ophthalmol. 1958;36:419-23. Klapper RM. Q-switched neodymium-YAG laser iridotomy. Ophthalmology 1984;91:1017-21. Kimbrough RL, Trempe CS, Brockburst RJ and Simmons RJ. Angle closure glaucoma in nanophthalmos. Am J Ophthalmol 1979;88:572-75. Ritch R, Liepmann J, Lizzi R, Tello C. Angle-closure glaucoma. In: Schumann JS. Imaging in Glaucoma. Slack incorporated. Thorofare, USA, 1997:185. Kjer B, Kessing SV. Trabeculotomy in juvenile primary open-angle glaucoma. Ophthalmic Surg 1993;24:663-68. Wilensky JT, Kaufman PL, Frohlichstein D, et al. Follow-up of angle-closure glaucoma suspects. Am J Ophthalmol 1993;115:338-46. Wilensky JT. Narrow angles accompanied by slit-lamp and gonioscopic evidence of risk are indications for prophylactic laser iridectomy. Surv Ophthalmol 1996;41:31-32. Ritch R. Definitive signs and gonioscopic visualization of appositional angleclosure are indications for prophylactic laser iridectomy. Surv Opthalmol 1996;41:33-36.

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References

20. Lundberg LU, Thygesen J, Damgaard-Jensen L, Serup L and Kessing SV. Glaucompatienter i behandling hos praktiserende Øjenlæger i Danmark. Ugeskr Læger 2000;162:3028-33. 21. Thygesen J, Kessing SV, Krogh E and Zibrandtsen P. Primært Åbenvinklet Glaucom & Oculær Hypertension. 1997; Dansk Glaucom Selskab. 22. Del Priore LV, Robin AL and Pollack IP. Neodymium:Yag and Argon laser Iridotomy. Long-term follow-up in a prospective randomized clinical trial. Ophthalmol 1988;95:1207-11. 23. Wetzel W, Schmidt-Erfurth U, Hæring G, et al. Laser sclerostomy ab externo using two different infrared lasers: a clinical comparison. German J Ophthalmol 1995;4:1-6. 24. Fleck BW. How large must an iridotomy be? Br J Ophthalmol 1990;74:58388. 25. Kessing SV and Brincher P. Argon Laser Iridoplasty of Plateau Iris caused Primary Angle Closure Glaucoma (a prospective consecutive clinical study). EGS Congress, Lissabon 1988 Abstr. 26. Joos KM . Case discussion: Management of Acute Angle-Closure Glaucoma. American Academy of Ophthalmology, Orlando 1999, Subspecialty Day. Abstr. 27. Ritch R, Tham CCY, Lam DSC. Long-term success of argon laser peripheral iridoplasty in the management of plateau iris syndrome. Ophthalmology 2004;111(1) 104-1088. 28. Foster PJ, Johnson GJ.Primary angle closure – classification and features. In Hitching RA, Lightman S. Fundamentals of clinical ophthalmology. Glaucoma. BMJ books, 2000;145-151. 29. American Academy of Ophthalmology: Primary angle closure. Preferred Practice Pattern, 2000. 30. Quigley HA, Congdon NG, Friedman DS. Glaucoma in China (and worldwide): changes in established thinking will decrease preventable blindness. Br J Ophthalmol 2001; 85:1271-1272. 31. Alsbirk PH. Anterior chamber depth in Greenland Eskimos. I. A population study of variation with age and sex. II. Geographical and ethnic variation. Acta Ophthalmol (Kbh) 1974;52:551-580. 32. Foster PJ, Devereux JG, Alsbirk PH, et al. Detection of gonioscopically occludable angles and primary angle closure glaucoma by estimation of limbal chamber deepth in Asians: modified grading scheme. Br J Ophthalmol 2000;84:186-92. 33. Rosman M, Aung T, Ang LPK et al. Chronic Angle-closure with glaucomatous damage. Long-term clinical course in a North American population and comparison with an Asian population. Ophthalmology 2002;109:2227-31. 34. Bonomi L, Marchini G, Maraffa M et al. Epidemiology of Angle-Closure Glaucoma. Prevalence, Clinical Types, and Association with Peripheral Anterior Chamber Depth in the Egna-Neumark Glaucoma Study. Ophthalmology 2000;107:998-1003. 35. He M, Foster PJ, JohnsonGJ et al. Angle-closure glaucoma in East Asian and European people. Different diseases? Eye advance on line publication, 21 January 2005;doi:10.1038/sj.eye.6701797.

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References 111 36. Matsunaga K, Ito K, Esaki K et al. Evaluation and comparison of indentation ultrasound biomicroscopy gonioscopy in relative pupillary block, peripheral anterior synechia and plateau iris configuration. J Glaucoma 2004;13(6):516519. 37. Goldsmith JA, Li Y, Chalita MR et al. Anterior chamber width measurement by high-speed optical coherence tomography. Ophthalmology2005;112:238244. 38. Kunimatsu S, Tomidokoro A, Mishima K et al. Prevalence of appositional angle closure determined by ultrasound biomicroscopy in eyes with shallow anterior chambers. Ophthalmology 2005;112:407-412. 39. Bhargova SK, Leighton DA, Phillips CI. Early angle-closure glaucoma. Distribution of irido trabecular contact and response to pilocarpin. Arch Ophhalmol 1973;89:369-372. 40. Dandona L, Dandona R, Mandal P et al. Angle-closure glacoma in an urban population in southern India. Ophthalmology 2000;107:1710-1716. 41. Ang LPK, Aung T, Chua WH et al. Visual field loss from primary angleclosure glaucoma: A comparative study of symptomatic and asymptomatic disease. Ophthalmology 2004;111:1636-1640. 42. Aung T, Nolan WP, Machin D et al. Anterior chamber depth and risk of primary angle closure in 2 east Asian populations. Arch Ophthalmol 2005;123:527532. 43. Thomas R, George R, Parikh R et al. Five year risk of progression of primary angle closure suspects to primary angle closure: a population based study. Br J Ophthalmol 2003;87:450-454. 44. Radhakrishnan S, Goldsmith J, Huang D. et al. Comparison of optical coherence tomography and ultrasound biomicroscopy for detection of narrow anterior chamber angles. Arch Ophthalmol 2005;123:1053-1059 45. Gordon MO, Beiser JA, Brandt JD, et al. The Ocular Hypertension Treatment Study: Baseline factors that predict the Onset of Primary Open Angle Glaucoma. Arch Ophthalmol 2002;120:714-720 46. Bourne RR, Alsbirk PH. Anterior chamber depth measurement by optical pachymetry: Systematic difference using the Haag-Streit attachments. Br J Ophthalmol 2006;90:142-145.

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112

References

RIGHTS OF ILLUSTRATIONS Below-mentioned sources have given the authors of this book permission to copy figures and originals. The rights of the remaining figures belong to the Glaucoma Clinic, Rigshospitalet Copenhagen University Hospital. Fig. 1. Norn MS. External eye, Methods of examination, Copenhagen, Scriptor; 1974: Fig. III,6. Fig. 2. Foster PJ, Devereux JG, Alsbirk PH, Lee PS, Uranchimeg D, Johnson GJ, Baasanhu J. Detection of gonioscopically occludable angles and primary angle closure glaucoma by estimation of limbal chamber depth in Asians: modified grading scheme. Br J Ophthalmol 2000; 84: Fig. 3+6. Fig. 4. Weekers R, Delmarcelle Y, Collignon J, Luyckx J. Mesure optique de la profondeur de la chambre anterieure applications cliniques. Documenta Ophthalmologica 1973; 34: 416. Fig. 7. Mandell AI. Gonioscopy. In: Heilmann K, Richardson KT. Glaucoma, conception of a disease, Stuttgart, Georg Thieme; 1978: Fig. 4.20. Fig. 9. Henkind P, Starita R, Tarrant T. Atlas of glaucoma, Fort Worth, Texas, Alcon laboratories, Inc.; 1984: plate 2. Fig. 11. Tegninger: Jørgen Kampp, Tellus Publishing, Denmark. Fig. 12. Mandell AI. Gonioscopy. In: Heilmann K, Richardson KT. Glaucoma, conception of a disease, Stuttgart, Georg Thieme; 1978: Fig. 4.24. Fig. 13. Mandell AI. Gonioscopy. In: Heilmann K, Richardson KT. Glaucoma, conception of a disease, Stuttgart, Georg Thieme; 1978: Fig. 4.26. Fig. 15a. Shaffer. Stereoscopic manual of gonioscopy, Saint Louis; CVMosby, 1962: Real I-2 p.43. Fig.15b. Mandell AI. Gonioscopy. In: Heilmann K, Richardson KT. Glaucoma, conception of a disease, Stuttgart, Georg Thieme; 1978: Fig. 4.26. Fig. 20. Becker og Shaffer. Diagnosis and therapy of the glaucomas, third edition Saint Louis: CVMosby; 1970: Fig.4-1. Fig. 22. Becker og Shaffer. Diagnosis and therapy of the glaucomas, third edition Saint Louis: CVMosby; 1970: Fig.13-1. Fig. 27. Ritch R, Liebmann JM. Laser iridotomy and peripheral iridoplasty. In Ritch R, Shields M, Krupin T. The glaucomas, second edition Saint Louis: Mosby; 1996: Fig. 76-23.

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Index 113

INDEX Acute glaucoma 1, 96 Acute PAC, treatment 96 principles of treatment 95 terminology 1 Acute/subacute PAC, mixed group 87 plateau iris 77 pupil block 59 Angle coloboma 26, 29, 39 Argon laser iridoplasty 102 complications 105 evaluation 80 indications, contraindications 103, 104 technique 104 Axenfeld’s anomaly 40, 42 Axial chamber depth measurement (ACD) 11 sources of error 16 plauteau iris 12 pupil block 12 Blood vessels in chamber angle, normal 40 pathological 43 Chamber angle, definitions 25 classification 25 normal anatomy 32 Scheie’s classification system 26 Chronic PAC, mixed group 87 plateau iris 78 pupilblock 61 Ciliary body 37 Corneal thickness (CT) 8 Corneoscleral trabecular meshwork 27 (fig. 9), 39 Dark-room test – prone position 45 Detection of PAC 7 Diagnostic procedures with PAC 11 Embryotoxon posterior 40 Fistulating operation 105 complications 106 indication 106 post-operative treatment 107 Glaucoma with PAC, definition 1, 50 Goldmann’s gonioscopy lens 23 Gonioscopy 16 terminology 28 (fig. 10) Gonioscopy methods with PAC 25

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Gonioscopy methodology with PAC, standardised 29 Imminent PAC, mixed group 86 plateau iris 76 pupil block 59 terminology 1 Indentation gonioscopy 18, 21 (fig. 7) Iridocorneal endothelial syndrome (ICE) 43 Iris contour 23, 33, 35 (fig. 14) Iris knee 27 (fig. 9), 34, 72 (fig. 23), 105 Iris processes 36, 38 (fig. 15) Latent PAC glaucoma, mixed group 89 plateau iris 78 pupilblock 62 terminology 1, 50 Limbal chamber depth measurement (LCD) 7 Manifest PAC glaucoma, mixed group 89 plateau iris 80 pupilblock 64 terminology 1, 50 Narrow angle, definition 26 Narrow occludable angle, definition 27 Narrow appositional-closed angle, definition 27 Narrow synechiae-closed angle, definition 28 Neovascularisation in the chamber angle 43 Open angle, definition 26 PAC with plateau iris 50, 51, 70, 71 (fig. 22) case histories 77 (3), 79 (4), 81 (5) detection, diagnosis 73 pathophysiology 71 subclassification and specific treatment 52 (fig. 19), 75 (fig. 24) PAC with pupil block 50, 55, 56 (fig. 20) case histories 63 (1), 66 (2) detection and diagnosis 57 pathophysiology 55 subclassification and specific treatment 52 (fig. 19), 58, 59 (fig. 21) PAC main and subclassification 52 (fig. 19) PAC main classification 49, 50, 51 (fig. 18) PAC subclassification 51, 52 (fig. 19) PAC mixed group, case histories 88 (6), 90 (7), 92 (8) detection, diagnosis 84 pathophysiology 84 pupil block and plateau iris 50, 84 subclassification, specific treatment 52 (fig. 19), 85 (fig. 25) Pachymetry, optical 13, 15 (fig. 4) ultrasound and laser 14, 15 Peripheral anterior synechiae (PAS) 38 (fig. 25), 41, 72 (fig. 23) Pigmentation of the chamber angle, abnormal 44 normal 39

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Index 115 Plateau iris with PAC 70 Posner’s indentation goniolens 18, 20 (fig. 6), 22 (fig. 8) Prevalence PAC Glaucoma 5 Preventative treatment of PAC 2 Primary angle-closure (PAC) 1 definition 50 Primary position at gonioscopy 21, 30 Provocation test 45 Pupil block with PAC 55 Rieger’s syndrome 40, 42 Sampoaolesis line 27 (fig. 9), 39, 41 (fig. 16) Schlemm’s canal 37, 38 (fig. 15) Schwalbe’s line 39, 72 (fig. 23) Scleral spur 27 (fig. 9), 38 Scleral limbal staphyloma 10 Secondary angle-closure (SAC) 12 Specific treatment of PAC, definition 3, 53 Suspect PAC, mixed group 85 plateau iris 76 pupil block 58 Ultrasound biomicroscopy (UBM) 46 Uveal meshwork 36 Van Herick 7 YAG-laser iridotomy 100, 102 (fig. 26) complications 102 evaluation 67 indications, contraindications 100 size 69 techniques 101

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PrimaryAngleClosure_def

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Pagina 1



S.V. Kessing and J.Thygesen

by Svend Vedel Kessing and John Thygesen

Kugler Publications, Amsterdam, The Netherlands

Primary Angle-Closure and Angle-Closure Glaucoma

Primary Angle-Closure and Angle-Closure Glaucoma

Glaucoma

Glaucoma

Glaucoma Screening

Glaucoma: Science and Practice

Glaucoma. Science and Practice

Glaucoma: Identification and Co-Management

Glaucoma Surgery

Management of Cataracts and Glaucoma

Glaucoma - Basic and Clinical Concepts

Atlas of Glaucoma

The Mystery of Glaucoma

Medical Treatment of Glaucoma

Pearls of Glaucoma Management

Non-Penetrating Glaucoma Surgery

Shields Textbook of Glaucoma (Allingham, Shields' Textbook of Glaucoma)

Atlas of Glaucoma, Second Edition

ICT and Primary Mathematics

Perception and Primary Qualities

Primary and Elementary Education

Ocular Blood Flow in Glaucoma

Primary Colors

School Violence and Primary Prevention

Classroom Pedagogy and Primary Practice

Renaissance and Reformation: Primary Sources

Primary Inversion

Primary Colors

Primary Colors

Primary Inversion

Primary Angle-Closure and Angle-Closure Glaucoma