Pediatric Ophthalmology, Neuro-Ophthalmology, Genetics: Strabismus - New Concepts in Pathophysiology, Diagnosis, and Treatment

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Essentials in Ophthalmology

Pediatric Ophthalmology, Neuro-Ophthalmology, Genetics B. Lorenz Editors

M. C. Brodsky

Essentials in Ophthalmology

Glaucoma

G. K. Krieglstein Series Editors

Cataract and Refractive Surgery

R. N. Weinreb

Uveitis and Immunological Disorders Vitreo-retinal Surgery Medical Retina Oculoplastics and Orbit Pediatric Ophthalmology, Neuro-Ophthalmology, Genetics Cornea and External Eye Disease

Editors Birgit Lorenz Michael C. Brodsky

Pediatric Ophthalmology, NeuroOphthalmology, Genetics Strabismus - New Concepts in Pathophysiology, Diagnosis, and Treatment

Series Editors

Volume Editors

Günter K. Krieglstein, MD Professor and Chairman Department of Ophthalmology University of Cologne Joseph-Stelzmann-Straße 9 50931 Köln Germany

Birgit Lorenz, MD Professor of Ophthalmology Klinik und Poliklinik für Augenheilkunde Justus-Liebig-University UKGM GmbH Giessen Campus Friedrichstraβe 18 35392 Giessen Germany

Robert N. Weinreb, MD Professor and Director Hamilton Glaucoma Center Department of Ophthalmology University of California at San Diego 9500 Gilman Drive La Jolla, CA 92093-0946 USA

ISBN: 978-3-540-85850-8

Michael C. Brodsky, MD Professor of Ophthalmology and Neurology Mayo Clinic Department of Ophthalmology 200 First Street SW Rochester, MN 55905 USA

e-ISBN: 978-3-540-85851-5

DOI: 10.1007/978-3-540-85851-5 Library of Congress Control Number: 2009938957 © Springer-Verlag Berlin Heidelberg 2010 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Product liability: The publishers cannot guarantee the accuracy of any information about dosage and application contained in this book. In every individual case the user must check such information by consulting the relevant literature. Cover design: wmx-Design, Heidelberg Printed on acid-free paper 9 8 7 6 5 4 3 2 1 (www.springer.com)

Foreword

The Essentials in Ophthalmology series represents an unique updating publication on the progress in all subspecialties of ophthalmology. In a quarterly rhythm, eight issues are published covering clinically relevant achievements in the whole field of ophthalmology. This timely transfer of advancements for the best possible care of our eye patients has proven to be effective. The initial working hypothesis of providing new knowledge immediately following publication in the peer-reviewed journal and not waiting for the textbook appears to be highly workable. We are now in the third cycle of the Essentials in Ophthalmology series, having been encouraged by read-

ership acceptance of the first two series, each of eight volumes. This is a success that was made possible predominantly by the numerous opinion-leading authors and the outstanding section editors, as well as with the constructive support of the publisher. There are many good reasons to continue and still improve the dissemination of this didactic and clinically relevant information.

G.K. Krieglstein R.N. Weinreb

Series Editors

Preface

The field of strabismology has long suffered from a discrepancy between its levels of sophistication in practice and theory. Although its diagnostic and therapeutic armamentarium has become quite advanced, the scientific understanding of disease pathogenesis has remained rudimentary. Consequently, educational training in strabismus diagnosis and treatment has become a didactic exercise in “learning the rules.” Recent advances in epidemiology, neuroimaging, genetics, and neurobiology have revolutionized our understanding of strabismus. Conceptualizing strabismus within an evolutionary framework has advanced our understanding of why it arises and provided new clues to its neurological underpinnings. As new information is consolidated, we are beginning to formulate a unified

philosophy of strabismus that integrates new concepts of pathogenesis into the clinic. This book provides a compendium of chapters that highlight new ideas in the field of strabismus. We have assembled an international panel of contributors who have advanced our understanding of strabismus pathogenesis. Some chapters are new while others are derived from recent seminal articles that have challenged our understanding of strabismus diagnosis and treatment. Original sources for these chapters are appropriately acknowledged. We thank our innovative authors for their important contributions, and hope that the reader finds this edition both stimulating and enlightening. Birgit Lorenz Michael C. Brodsky

Contents

Chapter 1 Epidemiology of Pediatric Strabismus Amy E. Green-Simms and Brian G. Mohney

2.1.3 2.2 2.2.1

1.1 1.2 1.2.1 1.2.1.1 1.2.1.2 1.2.1.3 1.2.1.4 1.2.1.5 1.2.2 1.2.2.1 1.2.2.2 1.2.2.3 1.2.2.4 1.2.2.5 1.2.3 1.3 1.4 1.4.1 1.4.2 1.5 1.6

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . Forms of Pediatric Strabismus . . . . . . . . . . Esodeviations . . . . . . . . . . . . . . . . . . . . . . . . . . Congenital Esotropia . . . . . . . . . . . . . . . . . . . Accommodative Esotropia. . . . . . . . . . . . . . Acquired Nonaccommodative Esotropia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Abnormal Central Nervous System Esotropia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensory Esotropia . . . . . . . . . . . . . . . . . . . . . . Exodeviations . . . . . . . . . . . . . . . . . . . . . . . . . . Intermittent Exotropia. . . . . . . . . . . . . . . . . . Congenital Exotropia . . . . . . . . . . . . . . . . . . . Convergence Insufficiency. . . . . . . . . . . . . . Abnormal Central Nervous System Exotropia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensory Exotropia . . . . . . . . . . . . . . . . . . . . . . Hyperdeviations . . . . . . . . . . . . . . . . . . . . . . . Strabismus and Associated Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Changing Trends in Strabismus Epidemiology . . . . . . . . . . . . . . . . . . . . . . . . . . Changes in Strabismus Prevalence . . . . . . Changes in Strabismus Surgery Rates . . . Worldwide Incidence and Prevalence of Childhood Strabismus . . . . . . . . . . . . . . . Incidence of Adult Strabismus . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 1 1 2 2

2.2.3 2 2 2 3 3 3 3 3 3 3

2.1.2

Binocular Alignment System. . . . . . . . . . . . Long-Term Maintenance of Binocular Alignment . . . . . . . . . . . . . . . . . Vergence Adaptation. . . . . . . . . . . . . . . . . . .

2.2.4 2.2.5 2.2.6 2.3 2.3.1 2.3.2 2.3.2.1 2.4

4 4 4 4 4 7 7

Chapter 2 Changes in Strabismus Over Time: The Roles of Vergence Tonus and Muscle Length Adaptation David L. Guyton 2.1 2.1.1

2.2.2

12 13 14

14 14 15 16 17 18 19 19 19

21 22

Chapter 3 A Dissociated Pathogenesis for Infantile Esotropia Michael C. Brodsky 3.1 3.2 3.3 3.4

11 3.5 11 12

Muscle Length Adaptation . . . . . . . . . . . . . Modeling the Binocular Alignment Control System. . . . . . . . . . . . . . Breakdown of the Binocular Alignment Control System. . . . . . . . . . . . . . Clarification of Unanswered Questions Regarding the Long-Term Binocular Alignment Control System. . . . . . . . . . . . . . . . . . . . . . . . . Changes in Strabismus as Bilateral Phenomena . . . . . . . . . . . . . . . . . . . Changes in Basic Muscle Length . . . . . . . . Version Stimulation and Vergence Stimulation . . . . . . . . . . . . . . . . . . Evidence Against the “Final Common Pathway”. . . . . . . . . . . . . . . . . . . . . Changes in Strabismus . . . . . . . . . . . . . . . . . Diagnostic Occlusion: And the Hazard of Prolonged Occlusion . . . . . . . . . Unilateral Changes in Strabismus . . . . . . . Supporting Evidence for Bilateral Feedback Control of Muscle Lengths. . . . Applications of Bilateral Feedback Control to Clinical Practice and to Future Research . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Dissociated Eye Movements . . . . . . . . . . . . Tonus and its relationship to infantile esotropia . . . . . . . . . . . . . . . . . . . Esotropia and Exotropia as a Continuum . . . . . . . . . . . . . . . . . . . . . . . . . . . Distinguishing Esotonus from Convergence . . . . . . . . . . . . . . . . . . . . . Pathogenetic Role of Dissociated Eye Movements in Infantile Esotropia . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

25 25 26 28 29 30

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Contents

Chapter 4 The Monofixation Syndrome: New Considerations on Pathophysiology Kyle Arnoldi 4.1 4.2 4.2.1 4.3 4.3.1 4.3.2 4.3.3 4.4 4.4.1 4.5 4.5.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . Normal and Anomalous Binocular Vision . . . . . . . . . . . . . . . . . . . . . . . . Binocular Correspondence: Anomalous, Normal, or Both?. . . . . . . . . . . MFS with Manifest Strabismus . . . . . . . . . . Esotropia is the Most Common form of MFS. . . . . . . . . . . . . . . . . . . . . . . . . . . . Esotropia Allows for Better Binocular Vision . . . . . . . . . . . . . . . . . . . . . . . . Esotropia is the Most Stable Form. . . . . . . Repairing and Producing MFS . . . . . . . . . . Animal Models for the Study of MFS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Primary MFS (Sensory Signs of Infantile-Onset Image Decorrelation) . . . Motor Signs of Infantile-Onset Image Decorrelation . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.1.10

5.1.11 33 33 34 35 35

5.1.1 5.1.2 5.1.3 5.1.4 5.1.5

5.1.6 5.1.7

5.1.8

5.1.9

Esotropia as the Major Type of Developmental Strabismus . . . . . . . . . . Early-Onset (Infantile) Esotropia . . . . . . . . Early Cerebral Damage as the Major Risk Factor . . . . . . . . . . . . . . . . . . . Cytotoxic Insults to Cerebral Fibers. . . . . . Genetic Influences on Formation of Cerebral Connections . . . . . Development of Binocular Visuomotor Behavior in Normal Infants. . . . . . . . . . . . . . . . . . . . . . . Development of Sensorial Fusion and Stereopsis . . . . . . . . . . . . . . . . . . Development of Fusional Vergence and an Innate Convergence Bias . . . . . . . . . . . . . . . . . . . . . . Development of Motion Sensitivity and Conjugate Eye Tracking (Pursuit/OKN) . . . . . . . . . . . . . Development and Maldevelopment of Cortical Binocular Connections . . . . . . . . . . . . . . . . .

5.1.13

5.1.14 5.1.15

35 36 36

5.1.16

37

5.1.17

38

5.1.18

38 39

5.2

5.2.1

Chapter 5 Visual Cortex Mechanisms of Strabismus: Development and Maldevelopment Lawrence Tychsen 5.1

5.1.12

5.2.2

41 41 41 42 42

42 43

6.1 6.2 6.2.1 6.2.2 6.2.3 6.2.4 6.2.5 6.3 6.4 6.5 6.5.1 6.5.2

44

44 46

46

46 47

47 50 50 50

51 52 52 54

Chapter 6 Neuroanatomical Strabismus Joseph L. Demer

44

44

Binocular Connections Join Monocular Compartments Within Area V1 (Striate Cortex) . . . . . . . . . . . . . . . . . Too Few Cortical Binocular Connections in Strabismic Primate. . . . . . Projections from Striate Cortex (Area V1) to Extrastriate Cortex (Areas MT/MST) . . . . . . . . . . . . . . . . . . . . . . . . Inter-Ocular Suppression Rather than Cooperation in Strabismic Cortex . . . . . . . . . . . . . . . . . . . . Naso-Temporal Inequalities of Cortical Suppression . . . . . . . . . . . . . . . . . Persistent Nasalward Visuomotor Biases in Strabismic Primate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Repair of Strabismic Human Infants: The Historical Controversy . . . . . . Repair of High-grade Fusion is Possible. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timely Restoraion of Correclated Binocular Input: The Key to Repair . . . . . . Visual Cortex Mechanisms in Micro-Esotropia (Monofixation Syndrome) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Neuroanatomic Findings in Area V1 of Micro-Esotropic Primates . . . . Extrastriate Cortex in Micro-Esotropa. . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.5.3 6.6

General Etiologies of Strabismus. . . . . . . . Extraocular Myopathy . . . . . . . . . . . . . . . . . . Primary EOM Myopathy . . . . . . . . . . . . . . . . Immune Myopathy . . . . . . . . . . . . . . . . . . . . . Inflammatory Myositis. . . . . . . . . . . . . . . . . . Neoplastic Myositis. . . . . . . . . . . . . . . . . . . . . Traumatic Myopathy . . . . . . . . . . . . . . . . . . . Congenital Pulley Heterotopy . . . . . . . . . . Acquired Pulley Heterotopy . . . . . . . . . . . . “Divergence Paralysis” Esotropia . . . . . . . . Vertical Strabismus Due to Sagging Eye Syndrome . . . . . . . . . . . . . . . . . Postsurgical and Traumatic Pulley Heterotopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . Axial High Myopia. . . . . . . . . . . . . . . . . . . . . . Congenital Peripheral Neuropathy: The Congenital Cranial Dysinnervation Disorders (CCDDs) . . . . . .

59 59 59 60 61 61 61 62 63 64 65 65 65

66

Contents

6.6.1 6.6.2 6.6.3 6.6.4 6.6.5 6.7 6.7.1 6.7.2 6.7.3 6.7.4 6.8 6.8.1 6.8.2 6.8.3

Congenital Oculomotor (CN3) Palsy. . . . . Congenital Fibrosis of the Extraocular Muscles (CFEOM) . . . . . . . . . . . Congenital Trochlear (CN4) Palsy. . . . . . . . Duane’s Retraction Syndrome (DRS). . . . . . . . . . . . . . . . . . . . . . . . Moebius Syndrome . . . . . . . . . . . . . . . . . . . . Acquired Motor Neuropathy. . . . . . . . . . . . Oculomotor Palsy . . . . . . . . . . . . . . . . . . . . . . Trochlear Palsy . . . . . . . . . . . . . . . . . . . . . . . . . Abducens Palsy . . . . . . . . . . . . . . . . . . . . . . . . Inferior Oblique (IO) Palsy . . . . . . . . . . . . . . Central Abnormalities of Vergence and Gaze . . . . . . . . . . . . . . . . . . Developmental Esotropia and Exotropia . . . . . . . . . . . . . . . . . . . . . . . . . . Cerebellar Disease. . . . . . . . . . . . . . . . . . . . . . Horizontal Gaze Palsy and Progressive Scoliosis . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67 67 69 69 70 71 71 71 71 71 72 72 72

Chapter 8 The Value of Screening for Amblyopia Revisited Jill Carlton and Carolyn Czoski-Murray 8.1 8.2 8.2.1

8.2.1.1 8.2.1.2 8.2.1.3 8.2.1.4 8.2.2 8.2.3 8.2.4

72 72

8.3

8.3.1 8.3.2 8.3.3 8.3.4

Chapter 7 Congenital Cranial Dysinnervation Disorders: Facts and Perspectives to Understand Ocular Motility Disorders Antje Neugebauer and Julia Fricke

8.3.5 7.1

7.1.1

7.1.1.1 7.1.1.2 7.1.1.3 7.2

7.2.1

7.2.1.1 7.2.1.2

7.2.2

Congenital Cranial Dysinnervation Disorders: Facts About Ocular Motility Disorders . . . . . . . . . . . . . . . . . . . . . . The Concept of CCDDs: Ocular Motility Disorders as Neurodevelopmental Defects . . . . . . . . . . Brainstem and Cranial Nerve Development. . . . . . . . . . . . . . . . . . . . Single Disorders Representing CCDDs . . . . . . . . . . . . . . . . . . . Disorders Understood as CCDDs . . . . . . . . Congenital Cranial Dysinnervation Disorders: Perspectives to Understand Ocular Motility Disorders . . . . . . . . . . . . . . . Congenital Ocular Elevation Deficiencies: A Neurodevelopmental View . . . . . . . . . . . . . Brown Syndrome. . . . . . . . . . . . . . . . . . . . . . . Congenital Monocular Elevation Deficiency and Vertical Retraction Syndrome . . . . . . . . . . . A Model of some Congenital Elevation Deficiencies as Neurodevelopmental Diseases . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

77

77 78 78 81

8.3.6 8.4 8.4.1 8.4.2 8.4.3 8.4.4 8.4.5 8.4.6

83

8.4.7 8.4.8

83 83

8.4.9 8.5 8.5.1

87 8.5.2 89 91

8.5.3

Amblyopia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What Is Screening? . . . . . . . . . . . . . . . . . . . . . Screening for Amblyopia, Strabismus, and/or Refractive Errors. . . . . . . . . . . . . . . . . . . . . . . . Screening for Amblyopia . . . . . . . . . . . . . . . Screening for Strabismus . . . . . . . . . . . . . . . Screening for Refractive Error . . . . . . . . . . . Screening for Other Ocular Conditions . . Difference Between a Screening and Diagnostic Test . . . . . . . . . . . . . . . . . . . . Justification for Screening for Amblyopia and/or Strabismus . . . . . . . . . . Recent Reports Examining Pre-School Vision Screening . . . . . . . . . . . . Screening Tests for Amblyopia, Strabismus, and/or Refractive Error. . . . . . . . . . . . . . . . . . . . . . . . . Vision Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cover-Uncover Test. . . . . . . . . . . . . . . . . . . . . Stereoacuity . . . . . . . . . . . . . . . . . . . . . . . . . . . Photoscreening and/or Autorefraction . . . . . . . . . . . . . . . . . . . . . . . . . What to Do with Those Who Are Unable to Perform Screening Tests?. . . . . . . . . . . . . . . . . . . . . . . . Who Should Administer the Screening Program? . . . . . . . . . . . . . . . . Treatment of Amblyopia. . . . . . . . . . . . . . . . Type of Treatment . . . . . . . . . . . . . . . . . . . . . . Refractive Adaptation . . . . . . . . . . . . . . . . . . Conventional Occlusion . . . . . . . . . . . . . . . . Pharmacological Occlusion . . . . . . . . . . . . . Optical Penalization . . . . . . . . . . . . . . . . . . . . Effective Treatment of Amblyopia in Older Children (Over the Age of 7 Years). . . . . . . . . . . . . . . . Treatment Compliance . . . . . . . . . . . . . . . . . Other Treatment Options for Amblyopia. . . . . . . . . . . . . . . . . . . . . . . . . . Recurrence of Amblyopia Following Therapy . . . . . . . . . . . . . . . . . . . . . Quality of Life . . . . . . . . . . . . . . . . . . . . . . . . . . The Impact of Amblyopia Upon HRQoL. . . . . . . . . . . . . . . . . . . . . . . . . . . Stereoacuity and Motor Skills in Children with Amblyopia. . . . . . . . . . . . . Reading Speed and Reading Ability in Children with Amblyopia. . . . . .

95 96

96 97 97 97 97 97 98 98

100 100 100 101 101

102 102 103 103 103 104 104 104

104 105 105 105 106 106 106 106

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8.5.4 8.5.5 8.5.6 8.5.7 8.5.8

Impact of Amblyopia Upon Education. . . . . . . . . . . . . . . . . . . . . . . . Emotional Well-Being and Amblyopia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Impact of Strabismus Upon HRQoL. . . . . . . . . . . . . . . . . . . . . . . . . . . Critique of HRQoL Issues in Amblyopia . . . . . . . . . . . . . . . . . . . . . . . . . . The Impact of the Condition or the Impact of Treatment? . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10.2.4 106 107 107 108 108 109

9.1.1 9.1.2 9.2 9.2.1 9.2.2 9.2.3 9.3 9.3.1 9.3.2 9.3.3 9.4 9.4.1 9.4.2 9.4.3 9.5

Amblyopia and Amblyogenic Disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Early Detection of Amblyopia. . . . . . . . . . . Brückner’s Original Description . . . . . . . . . Corneal Light Reflexes (First Purkinje Images) . . . . . . . . . . . . . . . . . . Physiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . Shortcomings and Pitfalls . . . . . . . . . . . . . . Fundus Red Reflex (Brückner Reflex) . . . . Physiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . Possibilities and Limitations . . . . . . . . . . . . Pupillary Light Reflexes. . . . . . . . . . . . . . . . . Physiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Performance . . . . . . . . . . . . . . . . . . . . . . . . . . . Possibilities and Limitations . . . . . . . . . . . . Eye Movements with Alternating Illumination of the Pupils . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

113 113 114 114 114 115 115 115 116 119 120 120 121 121 121 122 122

Amblyopia Treatment 2009 . . . . . . . . . . . . . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . Epidemiology . . . . . . . . . . . . . . . . . . . . . . . . . . Clinical Features of Amblyopia. . . . . . . . . . Diagnosis of Amblyopia . . . . . . . . . . . . . . . . Natural History . . . . . . . . . . . . . . . . . . . . . . . . . Amblyopia Management . . . . . . . . . . . . . . . Refractive Correction . . . . . . . . . . . . . . . . . . . Occlusion by Patching. . . . . . . . . . . . . . . . . . Pharmacological Treatment with Atropine . . . . . . . . . . . . . . . . . . . . . . . . . .

11.1 11.1.1 11.1.2 11.1.3

11.1.4 11.1.5 11.2 11.2.1 11.2.2 11.2.3 11.2.4 11.2.5

11.3 125 125 125 126 126 127 127 127 128 129

130 131 131 131 131 132 132 132 133 133 133 134

Chapter 11 Best Age for Surgery for Infantile Esotropia: Lessons from the Early vs. Late Infantile Strabismus Surgery Study H. J. Simonsz and G. H. Kolling

11.2.6

Chapter 10 Amblyopia Treatment 2009 Michael X. Repka 10.1 10.1.1 10.1.2 10.1.3 10.1.4 10.1.5 10.2 10.2.1 10.2.2 10.2.3

10.4 10.4.1 10.4.2 10.5 10.5.1

Chapter 9 The Brückner Test Revisited Michael Gräf 9.1

10.3 10.3.1 10.3.2 10.3.3 10.3.4

Pharmacological Therapy Combined with a Plano Lens. . . . . . . . . . . . Other Treatment Issues . . . . . . . . . . . . . . . . . Bilateral Refractive Amblyopia . . . . . . . . . . Age Effect. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Maintenance Therapy . . . . . . . . . . . . . . . . . . Long-Term Persistence of an Amblyopia Treatment Benefit. . . . . . . . Other Treatments . . . . . . . . . . . . . . . . . . . . . . Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Levodopa/Carbidopa Adjunctive Therapy . . . . . . . . . . . . . . . . . . . . Controversy. . . . . . . . . . . . . . . . . . . . . . . . . . . . Optic Neuropathy Rather than Amblyopia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11.3.1 11.3.2 11.3.3 11.3.4

11.3.5

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . Definition and Prevalence . . . . . . . . . . . . . . Sensory or Motor Etiology . . . . . . . . . . . . . . Pathogenesis: Lack of Binocular Horizontal Connections in the Visual Cortex. . . . . . . . . . . . . . . . . . . . . History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Outcome Parameters . . . . . . . . . . . . . . . . . . . Outcome of Surgery in the ELISSS. . . . . . . Reasons for the ELISSS. . . . . . . . . . . . . . . . . . Summarized Methods of the ELISSS. . . . . Summarized Results of the ELISSS . . . . . . Binocular Vision at Age Six. . . . . . . . . . . . . . Horizontal Angle of Strabismus at Age Six . . . . . . . . . . . . . . . . . . Alignment is Associated with Binocular Vision . . . . . . . . . . . . . . . . . . . Number of Operations and Spontaneous Reduction into Microstrabismus Without Surgery. . . . . . . The Number of Operations Per Child and the Reoperation Rate in the ELISSS. . . . . . Reported Reoperation Rates . . . . . . . . . . . . Test-Retest Reliability Studies . . . . . . . . . . . Relation Between the Postoperative Angle of Strabismus and the Reoperation Rate. . . . . . . . . . . . . . . . . . . . . . . Scheduled for Surgery, but no Surgery Done at the End of the Study at the Age of Six Years . . . . . . . . . . . .

137 137 137

138 138 138 139 139 139 140 140 140 141

142 142 142 144

145

145

Contents

11.3.6 11.3.7 11.3.8

Spontaneous Reduction of the Angle. . . . . . . . . . . . . . . . . . . . . . . . . . . . Predictors of Spontaneous Reduction into Microstrabismus . . . . . . . . Random-Effects Model Predicting the Angle and its Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

146 146

146 149 149

Chapter 12 Management of Congenital Nystagmus with and without Strabismus Anil Kumar, Frank A. Proudlock, and Irene Gottlob

12.3.6.2 12.3.6.3 12.3.6.4 12.3.6.5

12.1.1.1 12.1.2 12.1.2.1 12.1.3 12.1.3.1

12.2 12.2.1 12.2.2 12.2.3 12.2.3.4 12.2.3.5

12.2.3.6 12.2.3.7 12.3 12.3.1 12.3.1.1 12.3.1.2 12.3.1.3 12.3.1.4 12.3.2 12.3.3 12.3.4 12.3.5 12.3.6 12.3.6.1

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Congenital Nystagmus with and Without Sensory Deficits . . . . . . . . . . . The Clinical Characteristics of Congenital Nystagmus. . . . . . . . . . . . . . . Manifest Latent Nystagmus (MLN) . . . . . . Clinical Characteristics of Manifest Latent Nystagmus (MLN). . . . Congenital Periodic Alternating Nystagmus (PAN). . . . . . . . . . . . . . . . . . . . . . . Clinical characteristics of congenital periodic alternating nystagmus . . . . . . . . . . . . . . . . . Compensatory Mechanisms . . . . . . . . . . . . Dampening by Versions . . . . . . . . . . . . . . . . Dampening by Vergence . . . . . . . . . . . . . . . Anomalous Head Posture (AHP) . . . . . . . . Measurement of AHP. . . . . . . . . . . . . . . . . . . Effect of Monocular and Binocular Visual Acuity Testing on AHP. . . . . . . . . . . . . . . . . . . . . . . . . Testing AHP at Near . . . . . . . . . . . . . . . . . . . . The Effect of Straightening the Head in Patients with AHP . . . . . . . . . . Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Optical Treatment . . . . . . . . . . . . . . . . . . . . . . Refractive Correction . . . . . . . . . . . . . . . . . . . Spectacles and Contact Lenses (CL). . . . . . . . . . . . . . . . . . . . . . . . . . . . . Prisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low Visual Aids. . . . . . . . . . . . . . . . . . . . . . . . . Medication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acupuncture. . . . . . . . . . . . . . . . . . . . . . . . . . . Biofeedback . . . . . . . . . . . . . . . . . . . . . . . . . . . Botulinum Toxin-A (Botox). . . . . . . . . . . . . . Surgical Treatment of Congenital Nystagmus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Management of Horizontal AHP . . . . . . . .

13.1 13.2

154 154

13.2.2

156 157

13.2.3 13.2.4

157 13.2.5 158 13.2.6 159 160 160 160 160 160

161 162 162 162 162 162

13.3 13.4

13.5

164 165

168 169

Dissociated Deviations . . . . . . . . . . . . . . . . . Surgical Alternatives to Treat Patients with DVD . . . . . . . . . . . . . . . . . . . . . . Symmetric DVD with Good Bilateral Visual Acuity, with No Oblique Muscles Dysfunction . . . . . . . . . . . . . . . . . . . Bilateral DVD with Deep Unilateral Amblyopia . . . . . . . . . . . . . . . . . . . DVD with Inferior Oblique Overaction (IOOA) and V Pattern . . . . . . . . DVD with Superior Oblique Overaction (SOOA) and A Pattern . . . . . . . Symmetric vs. Asymmetric Surgeries for DVD . . . . . . . . . . . . . . . . . . . . . . DVD with Hypotropia of the Nonfixating Eye . . . . . . . . . . . . . . . . . . . . . . . . Dissociated Horizontal Deviation . . . . . . . Dissociated Torsional Deviation. Head tilts in patients with Dissociated Strabismus . . . . . . . . . . . . . . . . . Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

174 175

175 175 176 177 178 178 179

180 182 182

Chapter 14 Surgical Implications of the Superior Oblique Frenulum Burton J. Kushner and Megumi Iizuka 14.1 14.2 14.2.1

162 163 163 163 164 164 164

166 167 167

Chapter 13 Surgical Management of Dissociated Deviations Susana Gamio

13.2.1 12.1 12.1.1

Management of Vertical AHP . . . . . . . . . . . Management of Head Tilt. . . . . . . . . . . . . . . Artificial Divergence Surgery . . . . . . . . . . . Surgery to Decrease the Intensity of Nystagmus . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14.2.2

14.2.3

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . Clinical and Theoretical Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . The Effect of Superior Rectus Muscle Recession on the Location of the Superior Oblique Tendon Before and After Cutting the Frenulum. . . . . . . . . The Effect of the Frenulum on Superior Oblique Recession Using a Suspension Technique. . . . . . . . . . The Theoretical Effect of the Superior Oblique Frenulum on the Posterior Partial Tenectomy of the Superior Oblique . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

185 186

186

188

189 192

xiii

xiv

Contents

Chapter 15 Pearls and Pitfalls in Surgical Management of Paralytic Strabismus Seyhan B. Özkan 15.1

15.1.1 15.1.2 15.1.3 15.1.4 15.2 15.2.1 15.2.2 15.3 15.4

General Principles of Surgical Treatment in Paralytic Strabismus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Aims of Treatment. . . . . . . . . . . . . . . . . . . . . . Timing of Surgery . . . . . . . . . . . . . . . . . . . . . . Preoperative Assessment . . . . . . . . . . . . . . . Methods of Surgical Treatment . . . . . . . . . Third Nerve Palsy. . . . . . . . . . . . . . . . . . . . . . . Complete Third Nerve Palsy . . . . . . . . . . . . Incomplete Third Nerve Palsy . . . . . . . . . . . Fourth Nerve Palsy . . . . . . . . . . . . . . . . . . . . . Sixth Nerve Palsy . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16.2 16.3 16.3.1 16.3.1.1 16.3.1.2 16.3.1.3 195 195 195 196 197 198 198 199 200 204 205

Chapter 16 Modern Treatment Concepts in Graves Disease Anja Eckstein and Joachim Esser 16.1 16.1.1 16.1.2 16.1.2.1 16.1.3 16.1.3.1 16.1.3.2 16.1.3.3 16.1.4

Graves Orbitopathy (GO): Pathogenesis and Clinical Signs. . . . . . . . . Graves Orbitopathy is Part of a Systemic Disease: Graves Disease (GD) . . . . . . . . . . . Graves Orbitopathy−Clinical Signs . . . . . . Clinical Changes Result in Typical Symptoms. . . . . . . . . . . . . . . . . . . . . . Clinical Examination of GO . . . . . . . . . . . . . Signs of Activity . . . . . . . . . . . . . . . . . . . . . . . . Assessing Severity of GO . . . . . . . . . . . . . . . Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classification of GO. . . . . . . . . . . . . . . . . . . . .

16.3.1.4 16.3.1.5

16.3.1.6 16.3.2 16.3.2.1 16.3.2.2 16.3.2.3 16.4 16.4.1 16.4.2

207 16.5 207 208 208 208 208 209 211 211

16.5.1 16.5.2 16.6 16.6.1 16.6.2 16.6.3

Natural History . . . . . . . . . . . . . . . . . . . . . . . . . Treatment of GO . . . . . . . . . . . . . . . . . . . . . . . Active Inflammatory Phase . . . . . . . . . . . . . Glucocorticoid Treatment . . . . . . . . . . . . . . Orbital Radiotherapy . . . . . . . . . . . . . . . . . . . Combined Therapy: Glucocorticoids and Orbital Radiotherapy. . . . . . . . . . . . . . . Other Immunosuppressive Treatments and New Developments . . . . . . . . . . . . . . . . Therapy of Dysthyroid Optic Neuropathy [DON] and Sight-Threatening Corneal Breakdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . Other Simple Measures that may Alleviate Symptoms . . . . . . . . . . . . . . . Inactive Disease Stages. . . . . . . . . . . . . . . . . Orbital Decompression . . . . . . . . . . . . . . . . . Extraocular Muscle Surgery. . . . . . . . . . . . . Lid Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thyroid Dysfunction and GO. . . . . . . . . . . . Association Between Treatment of Hyperthyroidism and Course of GO . . . . . Relationship Between TSH-Receptor-Antibody (TRAb) Levels and Orbitopathy. . . . . . . . . . . . . . . . . Environmental and Genetic Influence on the Course of GO . . . . . . . . . . Relationship Between Cigarette Smoking and Graves Orbitopathy. . . . . . . Genetic Susceptibility . . . . . . . . . . . . . . . . . . Special Situations . . . . . . . . . . . . . . . . . . . . . . Euthyroid GO . . . . . . . . . . . . . . . . . . . . . . . . . . Childhood GO. . . . . . . . . . . . . . . . . . . . . . . . . . GO and Diabetes . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

212 213 213 213 213 213 213

214 214 215 215 216 217 220 220

220 221 221 221 222 222 222 222 223

Contributors

Kyle Arnoldi

Susana Gamio

Ross Eye Institute Department of Ophthalmology, University at Buffalo, Ross Eye Institute, 1176 Main Street, NY, 14209, USA

Gallo 1330, Ricardo Gutierrez Children’s Hospital, Matienzo 1731 First Floor E, Buenos Aires, Captial Fedral 1426, Argentina, South America

Michael C. Brodsky

Irene Gottlob

Departments of Ophthalmology and Neurology, Mayo Clinic 200 First Street, SW Rochester, MN 55905, USA

Jill Carlton

Department of Ophthalmology, Ricardo Gutiérrez Children’s Hospital, Buenos Aires, Argentina

Health Economics and Decision Science, CHARR, University of Sheffield, Regent Court, 30 Regent Street, Sheffield, S1 4DA, UK

Michael Gräf

Carolyn Czoski-Murray

Amy E. Greenberg

Leeds Institute of Health Sciences, University of Leeds, Room 1.26, 6 Charles Thackrah Building, 101 Clarendon Road, Leeds LS2 9LJ, UK

Department of Ophthalmology, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA

Joseph L. Demer Jules Stein Eye Institute, 100 Stein Plaza, UCLA, Box 957002, Los Angeles, CA 90095-7002, USA

Anja Eckstein University Eye Hospital, Hufelandstraβe 55, 45122 Essen, Germany

Marinus J.C. Eijkemans Department of Public Health, Erasmus Medical Center, PO Box 2040, 3000 CA, Rotterdam, The Netherlands

Department of Ophthalmology, Justus-Liebig-University Giessen, Giessen Campus, Friedrichstraβe 18, 35385 Giessen, Germany

David L. Guyton The Krieger Children’s Eye Center at the Wilmer Institute, The Johns Hopkins University School of Medicine, Baltimore, MD 21287-9028, USA

Megumi Iizuka University of Toronto, St. Michael’s Hospital, 61 Queen Street East, 8th Floor, Care of the Eye Clinic, Toronto, ON, Canada M5C 2T2

Gerold H. Kolling Department of Ophthalmology, University Clinic Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany

A. S. Anil Kumar Julia Fricke Department of Ophthalmology, Kerpener Straβe 62, 50937 Köln, Germany

Department of Ophthalmology, University of Leicester, UK

xvi

Contributors

Burton J. Kushner

Frank A. Proudlock

Department of Ophthalmology and Visual Sciences, 2870 University Avenue, Suite 206, Madison, WI 53705, USA

Department of Ophthalmology, Ricardo Gutiérrez Children’s Hospital, Buenos Aires, Argentina

Birgit Lorenz

Michael X. Repka

Department of Ophthalmology, Justus-Liebig-University Giessen Giessen Campus Friedrichstraβe 18, 35392 Giessen Germany

Brian G. Mohney Department of Ophthalmology, Mayo Clinic, 200 First Street Southwest, Rochester, MN 55905, USA

Antje Neugebauer Department of Ophthalmology, Kerpener Straβe 62, 50937 Köln, Germany

Seyhan B. Özkan Guzelhisar Mah. 35. sok. No: 8/A, 09010 Aydin, Turkey

Johns Hopkins University School of Medicine, Wilmer 233, Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, MD 21287-9028, USA

Huibert J. Simonsz Department of Ophthalmology, Erasmus Medical Center, PO Box 2040, 3000 CA Rotterdam, The Netherlands

Lawrence Tychsen St Louis Children’s Hospital at Washington University Medical Center, 1 Children’s Place, St Louis, MO 63110, USA

Chapter 1

Epidemiology of Pediatric Strabismus

1

Amy E. Green-Simms and Brian G. Mohney

Core Messages ■

■

■

■

■

Recognition and diagnosis of the individual forms of childhood strabismus are important for the best preservation of visual function. Esotropia is the most common form of pediatric ocular deviation in the West, whereas exotropia predominates in the East. Accommodative esotropia is the most prevalent form of strabismus in the West, comprising half of all esodeviations. Congenital, or infantile, esotropia accounts for less than 10% of all pediatric esotropia, a figure much smaller than once widely believed. Intermittent exotropia is the second most common form of childhood strabismus in the West

1.1

Introduction

Strabismus, or squint, is a disorder of ocular alignment. This overarching term may be further characterized by the direction of the misalignment: the prefix eso- describes an inward ocular deviation; exo-, an outward deviation; and hyper-, a vertical deviation. Descriptive suffixes include -tropia, a manifest deviation in which fusional control is not present, and -phoria, a latent deviation that is controlled by fusion. Strabismus detection, classification, and treatment are especially important in pediatric populations as strabismus is a leading factor in the development of amblyopia, or a loss in visual function resulting from inadequate or abnormal visual system stimulation. This strong connection with amblyopia differentiates pediatric from adultonset strabismus, wherein vision and stereopsis are less likely to be irreversibly harmed. In children, strabismus should be corrected to decrease the occurrence of amblyopia, to maximize the potential for stereopsis, and to straighten the visual axes of the eyes. This chapter will review recent data on the epidemiology of pediatric strabismus. The information will focus

■

■

■

and the most commonly diagnosed form of exodeviation worldwide. Hyperdeviations are uncommon, with fourth cranial nerve palsy being the most prevalent etiology. Major independent risk factors associated with strabismus development include: prematurity, central nervous system (CNS) impairment, low birth weight, family history, and refractive error. Recent studies have reported a decline in the number of surgeries performed for strabismus; however, population-based data of congenital esotropia in the United States confirms a more stable rate.

solely on tropic deviations rather than phorias and will encompass worldwide incidence and prevalence as well as clinical characteristics of the various strabismus subtypes.

1.2 Forms of Pediatric Strabismus 1.2.1

Esodeviations

Esodeviations are characterized by an intermittent or constant inward deviation of the eye or eyes (Fig. 1.1). Esotropia comprises approximately 60% of all strabismus in the West [1] whereas only about 30% in the East [2]. In the United States, children are diagnosed with esotropia at a mean age of 3.1 years [3], and 90% of esodeviations occur by 5 years of age [4]. Esotropia is more commonly associated with amblyopia than either exo- or hypertropia, occurring in one of three esotropic children vs. 1 of 12 exo- or hypertropic children [5]. There is no significant gender predilection among any of the following subtypes of childhood esotropia.

2

1

Epidemiology of Pediatric Strabismus

1.2.1.3

Acquired Nonaccommodative Esotropia

Acquired nonaccommodative esotropia defines children whose deviation develops after 6 months of age and is not associated with accommodative effort. This subtype has typically been thought of as uncommon and as portending underlying neurological disease. However, a recent population-based study showed that it is the second most common form of childhood esotropia [3], with an incidence of 1 in 257 children and is rarely the result of neurologic disease [8].

1

Fig. 1.1 A child with esotropia

1.2.1.4 1.2.1.1 Congenital Esotropia Congenital esotropia, also known as infantile or essential infantile esotropia, is generally defined as a neurologically intact child with a constant nonaccommodative esotropia that develops by 6 months of age. This term is often confusing as children do not typically present at birth with their deviation. Moreover, esotropia measuring up to 40 prism diopters (PD) between weeks 4 and 20 of life has been reported to resolve in 27% of children [6]. Congenital esotropia has, for decades, been considered the most common form of strabismus. However, more recent reports have demonstrated that congenital esotropia is much less common than once believed. In a recent incidence study among children born over a 30-year time period in the US, 1 in 403 live births developed congenital esotropia [7]. Other recent reports from the same population reported similar results, with infantile esotropia making up only 8.1% of all forms of esotropia [3].

1.2.1.2

Abnormal Central Nervous System Esotropia

Esotropic children with a developmental or neurologic disorder may be classified under central nervous system (CNS) defects regardless of the age at onset or form of esotropia. The most commonly associated conditions include cerebral palsy, developmental delay, Down syndrome, and seizure disorder. CNS-associated esotropia makes up approximately 10% of all diagnosed esodeviations [3].

1.2.1.5 Sensory Esotropia Sensory esotropia includes patients with a unilateral or bilateral ocular condition that prevents normal fusion. This form of esodeviation is commonly associated with anisometropic amblyopia as well as with disorders of deprivation such as cataract, corneal scarring, and retinal or optic nerve disorders [3].

Accommodative Esotropia

Accommodative esotropia is characterized by an acquired constant or intermittent deviation that is corrected or reduced 10 PD or more after wearing hyperopic spectacles full time for at least 3 weeks. Patients can further be classified as having fully accommodative esotropia, in which the deviation is reduced to ≤8 PD, or partially accommodative esotropia, in which there is a residual deviation of 10 or more PD. Accommodative esotropia, including both the partially and fully accommodative forms, comprises approximately one half of all pediatric esotropia in the United States and is the most prevalent form of childhood strabismus in the West [3]. This form of esodeviation has been reported to occur in 1 in 92 children [3].

Summary for the Clinician ■ ■

■

■

Accommodative esotropia comprises approximately half of all pediatric esotropia. Acquired nonaccommodative esotropia is the second most common form of esodeviation in the West and is rarely associated with neurologic disease. Congenital esotropia, once thought to be the most common esodeviation, makes up less than 10% of all esotropia diagnosed in childhood. Amblyopia occurs in one of three children with esotropia, a rate significantly higher than in children with either exotropia or hypertropia.

1.2

1.2.2

Exodeviations

Exotropia is a disorder of ocular alignment characterized by an outward deviation of the eye or eyes (Fig. 1.2). Exotropia is less common than esotropia among Western populations [1]; however, it is the predominant form of strabismus in the East [2]. Regardless of the relative prevalence, the age at presentation for children with exotropia tends to be older than for those with esotropia [4]. Amblyopia is less commonly associated with exotropia than esotropia [5].

1.2.2.1 Intermittent Exotropia Intermittent exotropia is an acquired, intermittent deviation of 10 or more PD unassociated with other ocular, paralytic, or neurologic disorders. It is the second most commonly diagnosed form of strabismus (at approximately 17%) in the United States [1] and the most commonly diagnosed subtype of exodeviation with an incidence of 1 in 155 children [9]. In a recent populationbased study, it was reported to occur nearly twice as often in girls compared with boys [10].

1.2.2.2 Congenital Exotropia Congenital exotropia includes children with a constant exodeviation that develops by 6 months of age. Although this condition is rare, many children will have associated neurologic or other disorders and should undergo CNS imaging [11]. This form of exotropia results in amblyopia much more often than other subtypes of divergent strabismus.

Forms of Pediatric Strabismus

3

exodeviation at near. It is the second most commonly diagnosed type of exodeviation and comprises approximately one in five children with exotropia [9] with an incidence of 1 in 411 children [9]. However, this disorder is likely to be under-diagnosed given the obscure symptoms and relatively imperceptible nature of the deviation to outside observers.

1.2.2.4

Abnormal Central Nervous System Exotropia

Exotropic children with a congenital or acquired developmental or neurological disorder may be grouped under CNS defects regardless of the age at onset. Approximately, 15% of children with exotropia may have neurologic abnormalities, most commonly cerebral palsy and developmental delay [9].

1.2.2.5 Sensory Exotropia Sensory exotropia includes children with a unilateral or bilateral ocular condition that prevents normal fusion, most commonly anisometropic amblyopia or cataract [9]. Children with sensory disturbances are more likely to develop exotropia (24 of 235 children, or 10.2%) than esotropia (15 of 221 children, or 6.8%) [12]. This difference may be in part due to the age at onset of visual impairment. Havertape and coauthors have shown that children with a unilateral or bilateral visual loss by 6 months of age are more likely to develop sensory esotropia, whereas those with an acquired visual loss are much more likely to develop sensory exotropia [13].

1.2.2.3 Convergence Insufficiency Convergence insufficiency describes children who are generally orthotropic at distance fixation but whose eyes do not converge sufficiently at near fixation, leaving an

Summary for the Clinician ■

■ ■

Exotropia is the predominant form of strabismus among Asian populations; however, it is less common than esotropia in the West. Intermittent exotropia is the most commonly diagnosed form of exodeviation. Amblyopia is less commonly associated with exotropia than esotropia.

1.2.3

Fig. 1.2 A child with exotropia

Hyperdeviations

Hypertropia, or a vertical displacement of one eye relative to the other, is the least diagnosed form of strabismus [1]. Nearly one-third of all cases are associated with fourth cranial nerve palsy (Fig. 1.3), corresponding to an incidence of 1 in 1,264 children [14]. Other causes of

4

1

Epidemiology of Pediatric Strabismus

a

1

included children with CNS disorders or acquired nonaccommodative esotropia, distinct forms of early-onset esotropia that have been shown to occur more frequently than infantile esotropia. Acquired nonaccommodative esotropia, on the other hand, appears to be relatively prevalent and is a form of esotropia that is much more likely to develop fusion and normal stereopsis with treatment [8]. Intermittent exotropia, the most common form of exodeviation, is more prevalent than any other form of strabismus in Asia and, as a result, may be the most prevalent form of strabismus worldwide.

b 1.4.2 Changes in Strabismus Surgery Rates

Fig. 1.3 A child with left fourth nerve palsy showing, (a) right head tilt and (b) left hypertropia with left head tilt

hypertropia include primary inferior oblique overaction, Brown syndrome, and CNS-associated hypertropia [14].

There have been several reports from the United Kingdom describing a decrease in the incidence of strabismus or strabismus surgery in recent years [21–24]. Explanations for this decline have included the implementation of childhood vision screening programs and the more frequent correction of the full hyperopic refractive error. Contrasting data, however, has come from Louwagie et al.’s population-based cohort study reporting on the incidence of infantile esotropia as well as the incidence of surgery for infantile esotropia in Rochester, Minnesota, US [7]. From 1965 through 1994, there was no significant change in the numbers of children diagnosed with infantile esotropia, and there was no significant change in the number of surgeries performed on these children.

Summary for the Clinician 1.3 Strabismus and Associated Conditions A number of studies have demonstrated an association between prenatal and environmental factors and the development of strabismus. Significant independent risk factors for strabismus include: family history, prematurity, low birth weight, low Apgar scores (at 1 and 5 min), maternal cigarette smoking, increasing maternal age, retinopathy of prematurity, refractive error, and anisometropia [15–20].

1.4 Changing Trends in Strabismus Epidemiology

■

■ ■

Congenital esotropia appears to be less prevalent than previously believed, whereas other forms such as acquired nonaccommodative esotropia are relatively common. Intermittent exotropia may be the most prevalent form of strabismus worldwide. The rate of pediatric strabismus surgery has recently been reported to be in decline; however, data from a population-based cohort of children with congenital esotropia in the United States found no change in strabismus incidence or surgical rate over a 30-year period (1965–1994).

1.4.1 Changes in Strabismus Prevalence Our understanding of the prevalence of childhood strabismus continues to change. As discussed earlier, congenital esotropia has recently been reported to occur less commonly than once widely believed, comprising only 8.1% of all diagnosed esodeviations [3]. The previously reported higher incidence of infantile esotropia may have

1.5 Worldwide Incidence and Prevalence of Childhood Strabismus Recent reports describe the prevalence of pediatric strabismus as ranging from 0.12% in 1.5-year-old Japanese children [25] to 20.1% in a cohort of low birth weight

1.5

5

Worldwide Incidence and Prevalence of Childhood Strabismus

Table 1.1. Pediatric strabismus prevalence rates by regions of the world Reference

Categorical

Number

Age of

Strabismus

Esotropia

Exotropia

Hypertropia

descriptions

of

subjects

prevalence

prevalence

prevalence

prevalence

within the

children

(years)

(%)

(%)

(%)

(%)

study

examined

North America Canada [31]

946

1.6–11.6

4.3

[32]

1,074