2011-2012 Basic and Clinical Science Course, Section 6: Pediatric Ophthalomology and Strabismus (Basic & Clinical Science Course)

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-Pediatric Ophthalmology and Strabismus

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Basic and Clinical Science Course

Pediatric Ophthalmology and Strabismus Section 6

2011-2012 ILast major revision 2010- 2011)

aD.. AMERICAN ACADEMY

I..:Y OF OPHTHALMOLOGY T"~ f)'t'

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The Basic and Cli nical Science Course is one component of the Li felong Education for the Ophthalmologist (LEO) framework, which assists mem bers in planni ng thei r continuing medical educati on. LEO includes an array of cl inica l education products that members may select to form individualized, self-directed learning plans for updating their clinical knowledge. Active members or fe llows who use LEO components may acc ulllulate sufficient CME cred its to earn the LEO Award. Contact the Academy's Cli nical Education Division for further information on LEO. The American Academy of Ophthalmology is accredited by the Accredit ation Council for Continuing Medical Ed ucation to provide continuing medical education for physicians. The American Academy of Opht halmology designates this enduri ng material for a maximum of 15 AMA PRA Category / Credits TM. Phys icians should claim only credit commensurate with the extent of their participation in the activity.

The Academy provides this material for educational purposes only. It is not in tended to represent the only or best method or procedure in eve ry case, nor to replace a physician's own judgment or give specific advice for case management. Incl uding all indica tions, contraindications, side effects, and alternative agents fo r each drug or treatment is beyond the scope of this material. All informat ion and recommendations should be verified, prior to use, with current information included in the manufac turers' package inserts or other independent sources, and considered in light of the patient's condition and history. Reference to certain drugs, instruments, and other prod ucts in th is course is made for illustrative purposes only and is not inte nded to constitu te an endorsement of sllch. Some material may include information on applications that are not considered community sta ndard, that reflect indications not included in approved FDA labeling, or that are approved for use only in restricted research sett ings. The FDA has stated that it is the responsibili ty of the physician to determine the FDA status of each d r ug or device he or she wishes to use, and to use th em with appropri ate, in formed patient consent in compliance with applicable law. The Academy specifically disclaims any and all liabil ity for injury or other damages of an)' kind, from negl igence or otherwise, for any and all claims that may arise from the use of any recommendations or other information contained herein.

Copyri ght © 20 11 American Academy of Ophthalmology All righ ts reserved Printed in Singapore

Basic and Clinical Science Course Gregory L. Skuta, MD, Oklahoma City, Oklahoma, Sellior Secretary for Clinical Education Louis B. Cantor, MD, Indianapolis, Indiana, Secretary for Ophthalmic Knowledge Jay ne S. Weiss, MD, Detroit, Michigan, BCSC Course Chair

Section 6 Faculty Responsible for This Edition Edwa rd L. Raab, MD, JD, Chair, New York, New York Aazy A. Aaby, MD, Portland, Oregon Jeffrey N. Bloom, MD, Cleveland, Ohio Jane C. Edmond, MD, Houston, Texas Gregg T. Lueder, MD, St Louis, Missouri Scott E. Olitsky, MD, Kansas City, Missouri Pa ul H. Phillips, MD, Little Rock, Arkansas Ken K. Nischal , MBBS, Consultant, London, Un ited Kingdom Robe rt E. Wiggins, MD, Asheville, North Carolin a Practicing Ophthalmologists Advisory Committee for Education T he Acade my wishes to acknowledge Samuel Markowitz, MD, Vision Rehabilitation Committee, for his rev iew of this edition. The Academy also wishes to acknowledge the foLlowing societies for recomme nding faculty members to the sese Section 6 comm ittee: the American Associat ion for Pediatric Ophthalmology and Strabismus; and th e Ameri can Acade my of Pediatrics, Sectio n on Ophthalmology.

Financial Disclosures T he authors state the following fina ncial relationships: Dr Bloom : WMR Biomedical, consultant, equity ow nershi p/stock options Dr Edmond: Inspire. consultant, lecturer/ honoraria recipient Dr N ischal: Massie Research Laboratories, lecturer/ hono raria recipient; Merck, lecturer/ honoraria recipient

Dr Wiggins: Ophthalmic Mutua l Insurance Company, consultant

The other authors state that they have no significant financial interest or other re lations hi p with the manufactu rer of any commerc ial product disc ussed in the chapte rs tha t they contri buted to th is course or with the manufacture r of any competing comme rcia l product.

Recent Past Faculty Arlene V. Drack. MD Amy K. Hutchinso n. MD David A. Plager. M D John W. Simon. M D In ad dition. the Academy gratefull y ack nowledges th e contributions of nu mero us past faculty and advisory comm ittee members who have played an important role in the development of previous editions of the Basic and Cli nical Science Course.

American Academy of Ophthalmology Staff Richard A. Zo rab. Vice President. Ophthalmic Knowledge Hal Straus, Director, Publications Department Ch ristine Arturo, Acquisitions Manager Stephanie Tanaka, Publications Manage r D. Jean Ray. Production Manager Brian Veen, Medical Editor Steven Huebner, Administrative Coordina to r

t:lD. AMERICAN ACA D EMV

~ OFOPHTHAl MOLOGV Tlu Eye M./). ;\ Slod ,/to on

655 Beach Street Box 7424 San Francisco. CA 94 120-7424

Contents General Introduction

xix

Objectives .

.1

Introduction-Rapport With Children: Tips for a Productive Examination

.3

Preparation . The Examination. Eyedrops Use of Topical Anesthesia for Foreign-Body Removal

. . . .

PART I Strabismus ... 1 Strabismus Terminology. PrefIxes and SuffIXes PrefIxes . SuffIxes . Strabismus Classification Terms

Fusional Status Variation of the Deviation With Gaze Posit jon or Fixating Eye. Fixation Age of Onset . . Type of Deviation . Abbreviated Designations for Types of Strabismus. Important Axes of the Eye .

3

3 5 5

.7 .9 .9 .9 10 10 10 10 II II II II

11

2 Anatomy of the Extraocular Muscles and Their Fascia.

13

Origin, Course, In sertion , Inn ervati on, and Action of the

Extraocular Muscles .

Insertion Relationships of the Rectus Muscles. Blood Supply of the Extraocular Muscles. Arterial System. .

13 13 14 14 15 16 16 16

Venous System Structure of the Extraocular Muscles

18 18

Horizontal Rectus Muscles. Vertical Rectus Muscles . . Oblique Muscles . . . . .

Levator Palpebrae Superioris Muscle.

v

vi • Contents

Orbital and Fascial Relationships Adipose Tissue . Muscle Cone. Muscle Capsule. The Tenon Capsule Pulley System. Anatomical Considerations During Surgery

3 Motor Physiology . Basic Principles and Terms.

Axes of Fick, Center of Rotation, and Listing's Plane. Positions of Gaze

Extraocular Muscle Action. Eye Movements. Motor Units Monocular Eye Movements. Binocular Eye Movements .

Supranuclear Control Systems for Eye Movement

4 Sensory Physiology and Pathology Physiology of Normal Binocular Vision Retinal Correspondence . Fusion.

Selected Aspects of the Neurophysiology of Vision Retinogeniculocortical Pathway.

Visual Development. Effects of Abnormal Visual Experience on the Retinogeniculocortical Pathway Abnormalities of Binocular Vision Confusion.

Diplopia. Sensory Adaptations in Strabismus Suppression

Anomalous Retinal Correspondence . Subjective Testing for Sensory Adaptations. Monofixation Syndrome.

5 Amblyopia. Classification.

Strabismic Amblyopia. Anisometropic Amblyopia Ametropic Amblyopia. Stimulus Deprivation Amblyopia Diagnosis Treatment. Cataract Removal . Refractive Correction

19 19 19 19 20 21 24

27 27 27 27 28 32 32 33 34 37

39 39 39 41 42 42 44 46 49 49 49 50 50 52 53 59

61 62 62 63 64 64 64 65 65 66

Contents . vii

Occlusion and Optical Degradation Complications of Therapy

6

Diagnostic Techniques for Strabismus and Amblyopia . . . . . . . . . . . . History and Characteristics of the Presenting Complaint. Assessment of Visual Acuity Distance Visual Acuity.

Near Visual Acuity Assessment of Ocular Alignme nt. Cover Tests . . . . . Light Reflex Tests. Dissimilar Image Tests .

Dissimilar Target Tests. Positions of Gaze . . Assessment of Eye Movements Ocular Rotations Convergence .

Fusional Vergence. Special Tests . Motor Tests . . . 3-Step Test. . . . Prism Adaptation Test. Tests of Binocular Sensory Cooperation

Worth 4-Dot Testing. Stereoacuity Testing. Cycloplegic Refraction. Adverse Effects .

7

Esodeviations Pseudoesotropia . Infantile (Co ngen ital) Esotropia Pathogenesis . . Management. . . . . Nystagmus and Esotropia . Accommodative Esotropia. Refractive Accommodative Esotropia

66 67

71 71 71 71 74 74 74 76 78 79 80 81 81 81

82 83 83 83 86 86 87 87 87 88

89 89 89 91 91 92 93 93

High Accommodative Convergence! Accommodative Esotropia.

94

Partiall y Accommodative Esotropia

95

Nonaccommodati ve Acquired Esotropia.

Basic (Acquired) Esotropia. Acute Esotropia. . CycUc Esotropia. .

95

95 96 96

Sensory Deprivation Esodeviation .

96

Divergence Insufficiency. . . . . Spasm of the Near Synkinetic Reflex. Su rgical (Consecutive) Esodeviation .

97 97 97

viii • Contents Incomitant Esotropia . _ . . . . . . . . . Sixth Cranial Nerve (Abd ucens) Paralysis. Other Forms of Incomitant Esotropia

8 Exodeviations

9

98 98 98

99 99 99 99 99

Pseudoexotropia . Exopho ri a . . . Intermittent Exotropia. Clinical Characteristics Evaluati on . . Classifi cation. Treatment Constant Exotropia. In fa ntile Exotropia Sensory Exotropia. Consecutive Exotropia. Exotropic Duane Syndrome Neuromuscu lar Abnormalities Dissociated Horizontal Deviation. Convergence Insufficiency. Convergence Paralysis. . . . . .

106 . 106

A- and V-Pattern Horizontal Strabismus .

107

Clinical Features and Identifi cation Management. . . . . . . . . Summary of Treatment Plans.

10 Vertical Deviations. Inferior Oblique Muscle Overaction. Clinica l Features. ..... Management. . . . . . . . . Superior Oblique Muscle Overaction Clinical Features . . . . Management. . . . . . . . . Oblique Muscle Pseudo-Overact ion . Dissociated Vertical Deviation Clinical Features . . . . . . . Management. . . . . . . . . Superior Oblique Muscle Paralysis (Palsy or Paresis). Clinical Features . . . . . . Management. Inferi or Oblique Muscle Paralys is. Clinical Features . . . Management. . Monocular Elevation Deficiency (Do uble Elevator Palsy). Clinical Featu res Management. . . .

100

101 101 103 104 104 105 105 105 105

107 110 11 2

113 11 3 114 114 11 5 115 116 11 6 11 6 116 11 7 11 8 11 8 120 121 122 122 123 123 124

Contents . ix

Orbital Floor Fractures Clin ica l Features Management.

11 Special Forms of Strabismus.

· 124 125 126

l27

Duane Syndrome. Clinical Features Management . Brown Syndrome. Clinical Featu res Management . Third Cranial Ne rve Paralysis Clinical Features Management. Sixth Cran ial Nerve Paralysis. Clin ica l Features Management . Thyroid Eye Disease. Cli nical Features Management. Chronic Progressive External Ophthal moplegia. Clinical Features Management. Myasthenia Gravis Clinical Features Management . Congen ital Fibrosis Syndrome Cli nical Features Management. Mobius Syndrome Clinical Features Management . Eso tro pi a Associa ted With High Myopia. In ternuclear Ophthalmoplegia Clin ical Features Management . Ocular Motor Apraxia. Clin ical Features Superior Oblique Myokymia. Clinical Features Management. Other Settings for Strabism us.

127 128 129 130 130 131 · 132 132 132 134 134 134 135 135 135 · 137 137 137 137 137 138 138 139 140 140 140 141 141 141 141 141 141 142 142 · 142 142 · 143

12 Surgery of the Extraocular Muscles.

145

Indications for Surgery Planning Consid erations . Visual Ac uity . Incomitance

145 145 145 146

x • Co ntents Cyclovertical Strabismus. Prio r Surgery. Surgical Techniques fo r the Muscles and Tendo ns . Weake ni ng Procedures. . Strengt hening Procedures Adjustable Sutures . . Pull-Over (Stay) Sutures. Transposition Procedu res Posterior Fixation. . . Guidelines fo r Strab ismus Surgery Esodeviation and Exodeviation Oblique Muscle Weakening Procedures Oblique Muscle Tighteni ng (Strengt hening) Proced ures Vertical Rectus Muscle Surge ry for Hypotropia and Hypert ropia . Other Rectus Muscle Surgery . . . Approaches to the Extraocular Muscles Fornix Incision . . . . Limbal or Peritomy Incision Complications of Strabismus Surgery Unsatisfactory Alignment Refractive Changes . . Diplopia . Perforation of the Sclera Postoperati ve Infec tions Foreign-Body Granuloma and Allergic Reaction. Conju nctival Incl usion Cyst Conjunctival Scarri ng Ad herence Syndro me . . Ddlffi . . Anterior Segment Ischemia. Change in Eyelid Position . ~U~~~~M=~

Anesthesia fo r Extraocular Muscle Surgery . Methods . . . . . . . Postoperative Nausea and Vomiting Oculocardiac Reflex . . . Malignant Hyperthermi a.

146 147 147 147 147 148 149 149 149 149 150 151 . 152 . 152 153 154 154 154 154 155 . 155 155 155 156 156 157 157 158 I~

158 159 I~

160 160 16 1 161 . 161

13 Chemodenervation Treatment of Strabismus and Blepharospasm Using Botulinum Toxin. Pharmacology and Mechanism of Action Indications, Techniques, and Results. Complications . . . . .

163 163 163 164

Contents • xi

PART II

Pediatric Ophthalmology . .

14 Growth and Development of the Eye Norm al Growth and Development Dimensions of the Eye. Refra ctive State. . . . . . . O rbi t an d Ocu lar Adnexa . . Iris. Pupil. and Ante ri or Cham ber. Int raocular Pressu re. Extraocular Muscle Anatomy and Phys iology . Retin a . . . . . . . .

Visual Acuity and Stereoacuity Abnormal Growth and Development

15 Orbital Dysmorphology and Eyelid Disorders. Termino logy and Associati ons of Abno rmal Interocula r Distance .

Hypotelorism. Hypertelorism Exorbitism. . Telecanthus. . Dystop ia Canthorum Eyelid Disorders Cryptophthalmos. . Congenital Coloboma of the Eyel id Ankyloblepharo n . Conge nital Ectropion Conge nital Entropio n Epiblepharon . Congenital Tarsal Ki nk . Distichiasis. . . Tri chotilloma n ia

Euryblepharon . Epicanthus. . . Palpebral Fissure Slants Blepharophimosis Syndrome. Ptosis . . . . . Marc us Gunn Jaw -Win kin g.

16 Infectious and Allergic Ocular Diseases Int ra uterine and Perinatal Infections of the Eye. Toxoplasmos is . . . . . . .

Rub ella . . Cytomegalic Inclusion Disease Herpes Simplex Infecti on. . . Syphilis . . . . . . Lymphocytic Cho riomeningitis.

165 167 . . . . . . .

167 167 169 169 169 170 170

. 170

. 170 . 17 1

173 . 173

173 173 173 174 175 175 175 175 176 176 176 · 176 · 176

. . · · · ·

· 177 177 · 177 177

· 178 · 178 178 · 180

181 · 18 1

· 18 1 · 183

· 184 · 185

· 185 · 186

xi i . Co ntents

Ophthalmia Neonatoru m Etiology . . Most Important Agents Prophylaxis for O phthalmia Neonatorum. Conjunctivitis ..... Bacterial Conjunctivitis Viral Conjunct ivitis Blepharitis. . . . . . Orbital and Ad nexal In fections. Preseptal Cellulitis O rb ital Celluli ti s Ocu lar Allergy . Seasonal Allergic Conjunctivitis. Vernal Keratoconjunctivit is. Atop ic Keratoconj unctivitis. Stevens-Johnson Syndrome Kawasaki Disease.

17

186 187 187 188 188 189 190 193 194 194 · 195 197 · 198 198 · 200 · 200 .20 1

The Lacrimal Drainage System

203

Developmental Anom alies. . Atres ia or Stenosis of the Lacrimal Puncta or Canaliculi Supernumerary Puncta . . Congenital Lacrimal Fistula Dacryocele. Clinical Features Management. Nasolacrimal Duct Obstruction. C linical Features . Nonsurgical Management Surgical Management

· 203 .203 · 204 · 204 · 204 · 204 · 205 · 205 · 205 · 206 · 206

18 Diseases ofthe Cornea and Anterior Segment.

211

Congenital Corneal Anomalies. . . . Abnorma li ties of Corneal Size and Shape. Peripheral Developmental Abnormalities: Anterior Segment DysgeneSiS. Central Corneal Developmental Abno rmalities Infantil e Corneal Opacit ies. Sclerocornea. ..... Tears, Breaks, or Ruptures of Descemet's Membrane Mucopolysaccha ridos is and Mucolipidosis Congenital Hereditary Endothelial Dystrophy. Dermoids ...... . Congenital or Infantile Gla ucoma. . . . Congenital Hereditary Stromal Dystrophy Corneal Ulcers Amniocentesis Treatment of Corneal Opacities.

.211 · 21 1 · · · · · · · · · · · · ·

212 214 2 16 216 217 217 217 2 18 2 18 2 19 2 19 219 219

Contents . xiii

Systemic Diseases With Co rneal Ma ni fes tatio ns in C hi ldhood Cystin osis ..... Hepatolenticul ar Degeneration Co nge nital Syphilis

Famili al Dysautonomia

19 Iris Abnormalities. Dyscoria . . . . . . Aniridia . . . . . .

Coloboma of the Iris Iris Nodules Lisc h Nod ul es . Juveni le Xa nthogranuloma.

Iris Mam illations . Primary Iris Cysts. Cysts of Iris Pigment Epithel iu m Central (Pupill ary) Cysts. Cysts of Iris St roma Second ary Iris Cysts. . Brushfield Spots . Pediatric I ris Heterochrom ia.

Persistent Pupi llary Memb ra nes Abnorm alit ies in th e Size. Shape. o r Locatio n of the Pupil Congeni tal Miosis. Congenital Mydriasis Ani socoria. . . . . Co rectopi a. . . . . Polycor ia and Pseud opolyco ri a Conge nital Iris Ectropion Iris Transillumi nat ion. Posterior Synechiae. . .

20 Pediatric Glaucomas Genetics.

Primary Congen ital Glaucoma Pathophys io logy . . . . Cli nica l Ma nifestat ions and Diagnosis Natu ral History.

Secondary Pediatric Glaucomas. Secondary to Ocular Anomalies. Seconda ry to System ic Disease .

Seconda ry Mechanical Glaucomas. O th er Secondary Glaucomas Ap hakic Glaucoma

Treatment . . . . . Surg ical T herapy Med ical T herapy PrognOSiS and Follow-Up

.220 · 220 · 220 .22 1 .22 1

223 · 223 · 223 · 224 .225 .225 · 226 · 226 · 226 · 226 .227 .227 .227 · 227 .227 · 228 · 228 · 228 · 229 · 229 · 230 · 230 · 23 1 · 23 1 .23 1

233 .233 . 233 .234 · 234 · 238 · 238 · 238 · 238 · 239 · 239 · 239 · 240 .240 .242 .243

xiv • Contents

21

22

Childhood Cataracts and Other Pediatric Lens Disorders .

245

Pediatric Cataracts Systemic Impl icatio ns Onset . . . Inheritance. Laterality. Morphology Persistent Fetal Vascu lature. Evaluation . . . Histo ry . . Visual Funct ion. . Ocular Examination, Workup Surgery. . . Ma nageme nt of the Anterior Caps ul e Lensectomy Witho ut intraocular Lens Impl antation Lensectomy With Int raoc ular Lens Implantat ion Intraocular Lens Implantation . . . . . Postoperative Care . . . . . . Visual Outcome After Cataract Ext raction Structural or Positional Lens Abnormalities Congenital Aphakia. Spherophakia. . . Colobom a Dislocated Lenses in C hildren Simple Ectopia Len tis . . Ectopia Lentis et Pupillae. Marfan Syndrome. . . . Homocystinuria . Weill-Marchesani Syndrome Sulfite Oxidase DefiCiency Treatment . . .

· 245 · 245 · 245 .246 .246 .246 · 250 · 250 · 251 · 252 · 252 · 253 · 254 .255 .255 · 257 .258 .259 · 260 .260 .260 .260 .260 · 261 · 262 · 262 · 263 · 263 .264 · 264 · 264

Uveitis in the Pediatric Age Group

267

Classification.. ..... . Anterior Uveitis . . . . . . . .... . Juvenile Idiopathic Arthritis .... . Tubulointerstitial NephritiS and Uveitis Syndrome. Orbital Pseudotumor . . . . . Other Causes of An terior Uveitis Intermediate Uve itis. Posterior Uveitis . Toxoplasmosis Toxocariasis Pan uvei tis. . . Sarcoidosis. Familial Juven ile SystemiC Granul omatosis

· 267 · 267 .267 · 27 1 .272 .272 .272 .272 .272 .273 .274 · 274 · 274

Contents • xv

Vogt-Koyanagi-Harada Syndrome . . . Other Causes of Posterior Uvei ti s and Pan uveitis

Masquerade Syndromes. Diagnos is of Pediatric Uveitis. Treatment of Pediat ri c Uve itis

Medical Management . . Surgical Treatment of Uveitis Complications

23

Vitreous and Retinal Diseases and Disorders

279

Ea rly-O nset Retinal Disease . . Persistent Feta l Vascu latu re. Retinopath y of Prematurity.

· 279 .279 .280 .287 · 288 . 289 · 29 1 · 29 1 .292 · 292 .292 . 292 · 293 .294 .294 .295 · 296 · 296 .296 .296 .296 .297 · 298 · 302 · 302 · 303 .304

Coats Disease .

Hereditary Retinal Disease. . . Leber Congenital Amaurosis Ac hromatopsia .

Congenital Stationa ry Night Blindness . Foveal Hypoplas ia. . . . . Aicard i Syndrome. Hereditary Macular Dystrophies Stargardt Disease . Best Disease . . . . . . .

Hereditary Vit reo retinopathies . Juve ni.le Retinoschisis _ .

Stickler Syndrome. . . . . Familial Exudative Vitreoretinopathy No rri e Disease

Goldmann -Favre Vitreo retinal Dystrophy Systemic Diseases and Disorders With Retinal Manifestati ons. Diabetes Mellitus Leukem.ia . Albinism. , . . . . Familial Oculorenal Syndromes. Neurometabo lic Disorders Gangliosidoses HI V/A IDS . . . . . . .

24

· 275 .275 · 275 · 275 · 275 .276 .278

Optic Disc Abnormalities

305

Developmental A no mali es . . . .

· 305 .305 .306 · 306 · 307 · 307 · 307 .308 · 309

Morning Glo ry Disc Anomaly Coloboma of the Optic Ne rve. Myelinated (Med uU ated) Retinal Ne rve Fibers Tilted Disc Syndro me Bergmeister Papilla . Megalopapilla. Optic Nerve Hypoplasia Optic Ne rve Aplasia.

xvi. Contents

Optic Ne rve Pits or Holes Peripapillary Staphyloma. Optic Atrophy . Dom inant Optic Atrophy. Behr Optic Atrophy. . . Leber Hereditary Optic Neuropathy . Optic Neur itis Pap illedema . . . . Idiopath ic Intracran ial Hyperten sion (Pse udotumor Cerebri) . Pseudopapilledema . Drusen . .

25

26

· 3 10 · 310 · 3 10 · 3 10 .3 11 · 3 11 · 311 · 312 · 312 · 3 13 · 314

Childhood Nystagmus

317

Nomenclature Evaluation. History Ocular Examinat ion. Ch ildhood Nystagm us Types. Co nge nital Nystagmus (Infantile Nystagmus Syndrome ) Acq uired Nystagmus Differential DiagnOSis Treatment. Prisms. Nystagmus Surgery Low Vision Rehab ilitation

· · · · . · · · · · · ·

317 3 18 318 318 320 32 1 324 326 326 326 328 330

Ocular and Periocular Tumors in Childhood

331

Orbital Tumors. . . . Differential Diagnos is Prim ary Ma lignant Neop lasms Metastatic Tumors. . ..... Benign Tumors. Ectopic Tissue Masses . C hildh ood Orbital Inflam mati ons . Eyelid an d Epibulbar Lesions. Papillomas . Conjunctival Epith elial Inclusion Cysts. Epi bulbar Limbal Dermoid Tumors Lipodermoid. . . . Conjunctival Nevi. . Co nge nital Nevocell ular Nev i of the Skin . Ocular Melanocytosis Inflammatory Conditions Intraocular Tumors . . . . Iris and Ciliary Body Lesio ns . C horoidal and Retina l Pigment Epithelial Lesions

· 33 1 · 33 1 · 334 · 336 · 338 · 343 · 346 · 347 · 348 · 348 .348 . 348 . 349 · 349 · 350 · 350 · 35 1 · 35 1 · 352

Contents. xv ii Leukemia Retinoblastoma.

27 Phakomatoses . Neurofibromatosis . Neurofibromatosis Type I Neurofi bromatosis Type 2 Tubero us Sclerosis . . von Hippel- Lindau Disease Sturge-Weber Syndrome. Ocular Involvement . Management. . Ataxia- Telangiectas ia . . Incontinentia Pigmenti . Wyburn-Mason Syndrome.

363 .363 · 365 · 37 1 .371 · 374 · 375 .377 .377 .378 .379 · 381

28 Craniofacial Malformations .

383

Craniosynostosis. . . . . Et iology of Craniosynostosis Craniosynostosis Synd romes. Crouzon Syndrome Aper t Syndrome . Saeth re-Chotzen Syndro me. Ocular Complications. Proptosis. . . . . Corneal Exposu re . Globe Luxation . Vis ion Loss. . . . Strabismus . Optic Nerve Abnormalities. Ocular Ad nexa Abnorma liti es Management.. ...... . Nonsynostotic Cran iofacial Condit ions Branchial Arch Syndromes. Pierre Robin Sequence. Fetal Alcohol Syndrome . .

· 383 .386 .387 · 387 · 388 · 388 · 388 .388 .388 .389 .390 · 390 · 391 · 39 1 .392 .392 .392 · 394 .394

29 Ocular Findings in Inborn Errors of Metabolism . Treatment.

..........

30 Ocular Trauma in Childhood Child Abuse Shaking Injury Superficial Injury . Penetrating Injury Blunt Injury . Hyphema Orbital Fractures \

· 354 .354

397 . 399

403 .404 .404 .407 .408 .409 .409 · 4 11

xviii • Contents

31 Decreased Vision in Infants and Children.

413

Normal Visual Development.. ..... Approach to the Infant With Decreased Vision . . . . . Pregen iculate Visual Loss. .

.413 . 414 .414 .4 15 .4 16 .4 16

RetrogeniclIlate Visual Loss, or Cortical VislIallmpairment.

Delayed Visual Maturation. Low Vision Rehabilitation Basic Texts. . Related Academy Materials Credit Reporting Form Study Questions Answers.

index.

.419 .421 .425 .429 .438 .443

General Introduction The Basic and Clinical Science Course (BCSC) is designed to meet th e needs of residents and practitioners for a comprehensive yet concise curriculum of the field of ophthalmology. The BCSC has developed from its original brief outline format, which relied heavil y on outside readings, to a more co nvenient and educat ionall y useful self-contained text.

The Academy updates and revises the course annually, with the goals of integrating the basic science and clinical practice of ophthalmology and of keeping ophthalmologists current w ith new developments in the var ious su bspecialties.

The BCSC incorporates the effort and expertise of more than 80 ophthalmologists, organized into 13 Section faculties, working wi th Academy editorial staff. In addition, the course continues to ben efit from many lasting contribu tion s made by th e fac ulties of pre-

vious editions. Members of the Academy's Practicing Ophthalmologists Advisory Committee for Education serve on each facu lty and, as a gro up, review every volume before and after major revisions.

Organization of the Course The Basic and Clinical Science Course comprises 13 volumes, incorporating fundamental ophthalmi c knowledge, subspecialty areas, and special topics: I 2 3 4 5 6 7

Update on General Medicine Fundamentals and PrinCiples of Ophthalmology Clinical Optics Ophthalmic Pathology and Intraocular Tumors Neura-Ophthalmology Ped iatric Ophthalmology and Strab ismus Orbit, Eyelids, and Lacrimal System

8 External D isease and Cornea 9 Intraoc ular lnflamrnation an d Uveit is

10 Glaucoma 11 Le ns and Catarac t 12 Retina and Vitreo us

13 Refractive Surge ry In addition, a comprehensive Master Index allows th e reader to eas ily lo cate subjects throughout th e en tire seri es.

References Read ers who wis h to explore specific topics in greater detail may consult the references cited within each chapter and listed in the Basic Texts section at the back of the book.

xix

xx • General Introduction

These references are intended to be selective rather than exhaustive, chosen by the BCSC faculty as being important, current, and readily available to res idents and practit ioners.

Related Academy educational materials are also listed in the appropriate sections. They include books, online and audiovisual materials, self-assessment programs, cli nical modules. and interactive programs.

Study Questions and CME Credit Each volume of the BCSC is designed as an independent study activity for ophthalmology residents and pract iti oners. The learning objecti ves for this volume are given on page 1. The text, illustrations, and references provide the information necessary to achieve the ob-

jectives; the stud y questions allow readers to test their unde rstanding of the materi al and their maste ry of the objectives. Physicians who wish to clai m CM E credit for this ed ucational act ivity may do so by mail. by fax, o r on lin e. The necessary forms and instructions

are given at the end of the book.

Conclusion The Basic and Clinical Science Course has expanded greall y over the yea rs, with the addition of much new text and numerous illustrati o ns. Recent editions have sought to place a greater emphasis on clinical applicability wh Ue main taining a solid foundation in basic science. As with any educa tional program, it re fl ec ts the ex perience of its authors. As its fac ulties change and as medicine progresses, new viewpo ints are always emerging on

controversial subjects and techniques. Not all alternate approaches can be included in this series; as with any educational endeavor, the learner should seek additional sources, including such carefully balanced opinions as the Academy's Preferred Practice Patterns. The BCSC facu lty and staff are continuously stri ving to improve the educational usefulness of the course; you, the reader, can contribute to this ongoing process. If yo u have any suggestions or questions abo ut the series, please do not hesitate to contact the faculty or the editors. The authors, ed itors, and reviewers hope that your stud y of the BCSC will be of lasting val ue and that each Section will serve as a practical resource for quality patient care.

Objectives Upo n completion of BCSC Secti on 6, Pediatric Ophthalmology and Strabismus, the reader shoul d be able to describe evaluation techniq ues for yo ung ch ild ren that provide the maxim um ga in of informa tio n with the leas t trauma and frustration

• outline the anatomy and phYSiology of the extraocular muscles and th eir fasc ia explain the classification, diagnosis. and treatme nt options for

amb lyopia descr ibe the common ly llsed diagnostic and measurement tests

for strabismus classify the various esodeviatiol1s and exodeviations. and describe the ma nagem ent of each type identify vertical strabismus and special forms of strabismus, and formulate a treatment plan for each type • list the poss ible complications of strabism us surgery, and describe gui deli nes to minimize them • d ifferent iate among variolls causes of conge nita l and acq ui red ocular infections in children, and formu late a logical plan for

the diagnosis and manageme nt of each type li st the most common diseases and ma lformations of the co rn ea, lacrimal drainage system , anterior segment, and iris seen in children • descr ibe th e d iagnostic fi nd in gs and treat me nt opt ions for

child hood glaucoma identify common types of childhood cataracts and other le ns disorders outline a diag nostic and manageme nt plan for ch ildhood catarac ts

\

identify appropr iate diagnostic tests for pediatric uveitis differentiate am ong vario us optic disc, yi treoretinal , and metabo lic diseases and disorde rs found in children

• describe the features of the va ri ous form s of nystagmus and understand their significance

• li st th e characteristics of ocular tum ors and phakomatoses seen in children describ e th e characteristic findin gs of accidental and nonaccide ntal childhood trauma design an approach to th e diagnosis of decreased vision in

children, and be fam iliar with the resources available to these patients

INTRODUCTION

Rapport With Children: Tips for a Productive Examination

Chi ldren are not merely small adults, and most common ophthalmologic problems in child ren are different from the most common problems in adults. The varying developmental le vels of children require different approaches to the ophthalmic examination. Proper preparatio n and attitude can make th e oph th almic exam ination of pediatric pa·

tients both enjoyable and rewarding.

Pre aration If at all possible, have a small room or corner of the waiting area designated for children. Both the parents and the adu lt patients will be relieved by this separation. A small table and chairs, some books. and some toys are sufficient.

A dedicated long pediatric examination lane with different types of distance fixation targets is optimal. Following the one toy, one look rule, have several small toys readily available for nea r flXation (Fig I- I). Light-colored plastic finger puppets become silent accommodative near targets that can also provide a corneal light reflex if placed over a muscle light or penlight. Some children fear the white coat. You may choose to enter th e room w ithout yours.

The Examination Examination of th e pediatric patient begins with observing children at ease in the play area, as they navigate th e ir way to the lane, and in the ir parent's arms as you enter the

room. This may be the best look yo u get before children cry and bury their face in the parent's shoulder. Observe the parents and Siblings. Some ophthalmic conditions tend to run in fami lies. Seat yo urself at the child's eye level and introduce yo urself to th e child and the parent. Establish and maintain eye contact with the child. Be relaxed, open, honest, and playfully engaging during the exa mination. Gaining the child's confiden ce makes for a faster and better examination, eas ier follow-up visits, and greater pare ntal support. Some children are more comfortable Sitting in a parent's lap.

Initiate ve rbal contact by asking child ren easy questions with simple answers. For example, children enjoy being regarded as "big" and correcting adu lts whe n they are wrong.

3

4 • Pediatric Ophthalmology and Strabismus

Figure 1-1

Small toys, pictures, and reduced letter and E cha rts are used as near fixation tar-

g ets. (Reproduced with permission from Haldi BA, Mets MB. Nonsurgical treatment of strabismus. Focal Points: Clini· ca l M odules for Ophtha lmologists. San Francisco: American Academy of OplHhalmology; 1997. module 4. Photograph courtesy of Berty Anne Haldi, CO.)

Tell them they look "so grow n up"; grossly overestimate their age or grade level and then ask, "Is th at ri ght'" A simple joke can relax both child and parent. To initiate physical contact with children, you can ask them to "give me five" or ad mire an article of their clothing, such as their shoes. Pushing the "magic button" on the nose of a child as you surre ptit iously activate video presentatio ns or mechanical ani mals with YOllr foot pedal allows you to work close to the child's face while he or she is distracted. Go where the action is- yo u m ay have o nl y a few mo ments of cooperation, so check what you most need to see at the beginning of the exami nation. If fusion is in doubt, check it first before disrupting it with other tests, including th ose for vision. While checking vision , make children feel successful by initially giving them objects they can readil y discern; then say, "That's too easy-let's try this one:' Copies of whatever oplotypes are appropriate for children (Allen cards, picture chart, tumbling E) can be given to the parent for at- home rehearsal to help di fferentiate not seeing the test object from not understand ing the test. Develop a different vocab ulary for wo rking wi th children , such as ") want to show yo u something special" instead of" J wa nt to examine yo u:' Use "magic sunglasses" fo r the Polaroid stereo glasses, "special flashligh t" for the retinoscope, "fun ny hat" for the indirect ophthalmoscope, and "magnifying glass" for the indirect lens. Confronta tion visua l fields can be performed as a counting-fin gers game o r Simo n Says. Talk children into a slit-lamp examination by saying that they can "dri ve the motorcycle" by having them grab the han dles of the slit lamp. Use your imagination to "play" with children as yo u rapidly proceed with the examination. Childre n will be more cooperative if yo u are sharing an experience instead of doing something to them. Save the most threatening or most unpleasant part of the examin ation for the end. The least expensive test yo u can order is a retur n office vis it. Children who become totally uncooperative can return later to fini sh the examination.

INTRODUCTION:

Rapport With Children: Tips for a Productive Examination.

5

For the follow-up examination of a child who was fussy during the firs t visit, ask the parent to bring the child in hungry and then feed him or her during the examination. When dealing with a vision-threatening or life-threatening problem, yo u must persist with the examination and even use sedation or anesthesia when necessary.

The answers to the most common pediatric ophthalmic problems seen in the office will usually be found in the cycloplegic examination. Almost all children are apprehensive about eyedrops. However, they do not have to like the drops; the important thing is to in still them. There are many approaches to giving eyed raps. If possible, someone other than the examini ng physician should administer the drops. Some practitioners use a cycloplegic spray, some use a topical anesthetic drop first, and some si mpl y use the cycloplegic drop. The drops can be described as being "li ke a splash of swimming pool water" that wi ll "feel funny fo r about 30 seconds:' Do not give ch ildren a long time to think about it. Dark irides are more difficult to dilate. In some cases, the parent can put the cycloplegic drops in at ho me, or the practitioner can perform an atropine refraction. (See Table 17-2 in BCSe Section 2, Fundamentals and Principles of Ophthalmology, for a complete listing of mydriatics and cycloplegics. See also Chapter 6 in this book. )

Use of Topical Anesthesia for Foreign-Body Removal Procedures that provoke anxiety or are pai nful are best performed if children k.now that it is possible to numb the area. For example, the follOWing process to remove foreign bodies can comfort the child: l. Explain to the child that the eyes can be made numb. 2. Show the child the drop to be used while telling him or her that the drop is cold but most children say it is also comfor table. You can call it a "magiC drop:' Put a drop on the back of the child's hand first, before putting the drop in the eye. Tell the patient he or she might have felt that first drop in the eye but probably wo n't notice a second drop so much because the eye is already numb. 3. Demonstrate with a second drop that the eye has become numb. Show the child that a soft cotton-tipped app licator with drops on it can to uch the eye without hurting or even bei ng felt. 4. Introduce instruments fo r foreign -body removal in the same way. Day SH, Sami DA. History, examination, and further investigation. In: Taylor 0 , Hoyt CS, eds. Pediatric Ophthalmology and Strabismus. 3rd ed. Cam bridge, MA: Saunders; 2005:66-77. McKeown CA. The ped iatric eye exami nation . In: Albert DM, Jakobiec FA, eds. Principles al1d Practice ofOphtha/l11ology. 2nd ed. Phil adelphi a: Saunders; 2000. Pediatric Ophthalmology Panel. Pediatric Eye Evaluations. Preferred Practice Patterns. San Francisco: Ame rican Academy of Ophthalmology; 2002.

1

CHAPTER

1

Strabismus Terminology

The term strabismus is derived from th e Greek wo rd strabismos, "to squint, to look

obliquely o r askance:' Strabismus mea ns ocular misalignment, wheth er caused by abnormalit ies in binocular vision or by anoma lies of neuromuscular cont rol of ocular motility. Many terms are e mployed in discussions of strabismus, and unless these terms are used correctly and uniform ly, confusion and misunderstand ing can occur. Orth ophoria is the ideal condition of ocular alignment und er binocular conditio ns. In

reali ty, o rth o phoria is seldom encou ntered; a small heteropho ria (see below) can be documented in most persons. Some ophthalmologists therefore prefer orthotropia to mean correct direction or positi on of the eyes. Both terms are common ly used to describe eyes without strabismus. Heterophoria is an ocular deviation kept latent by the fusional mechanism (latent strabismus). Heterotropia is a deviation that is manifest and not kept under control by the fusio nal mechanism (manifest strabismus).

It is important to identify the deviating eye, especially when seeking to call attention to the "offending" eye as causing the deviation. This usage is particularly helpful when dealing with vertical deviations, restrictive or paretic strabismus, or amblyopia in a preve rb al chil d.

Prefixes and Suffixes A detailed nomenclature has evolved to describe types of ocu lar deviations. T his vocabulary uses many prefixes and sufftxes based o n the relative positions of the visual axes of both eyes to account for the multiple strabismic patterns encountered.

Prefixes Eso- The eye is rotated so that the corn ea is deviated nasall y and the fovea is rotated tempo rally. Because the visual axes converge at a point closer than the fixat ion target, this is also known as convergent strabismus. Exo- The eye is rotated so that th e cornea is deviated temporall y and the fovea is rotated nasa ll y. Because the visual axes are still di ve rgi ng at th e fixation target, this is also known as divergent strabismus.

9

10 • Pediatric Ophthalmology and Strabismus The eye is rotated so that the cornea is deviated superiorly and the fovea is rotated inferiorly. This is also known as vertical strabismus.

Hyper-

The eye is rotated so that the cornea is deviated inferiorly and the fovea is rotated superiorly. This is also known as vertical strabismus. Hypo-

Incyclo- The eye is rotated so that the superior pole of the ve rtical meridian is torted nasall y and the inferior pole of the ve rtical meridian is torted temporally. This is also known as intorsionai strabismus.

The eye is rotated so that the superior pole of the vertical meridian is torted temporally and the inferior pole of the vertical meridian is torted nasally. This is also known as extorsionai strabismus.

Excyclo-

Suffixes A latent deviation (eg, esophoria, exophoria, right hyperphoria) that is controlled by the fu sional mechanism so that the eyes remain aligned under normal binocular

-phoria vision

A manifest deviation (eg, esotropia, exotropia, right hypertropia, excyclotropia) th at exceeds the control of the fusional mechanism so that the eyes are not aligned under

-tropia

binocular conditions

Strabismus Classification Terms No classification is perfect or all-inclusive, and several methods of classifyi ng eye alignment and motility disorders are used. FoUowing are terms used in these classifications.

Fusional Status Phoria

A latent deviation in which fusiona l control is always present

Intermittent tropia Tropia

A deviation in which fusiona l control is present part of the time

A manifest deviation in which fusional control is not present

Variation of the Deviation With Gaze Position or Fixating Eye The size of the deviatio n does not vary by more than a few prism diopters with direction of gaze or with the eye used for fixating.

Comitant Iconcomitant)

Incomitant (noncomitant) The deviation varies in size with the direction of gaze or wi th the eye used for fixating. Most incomitant st rabismus is paralytic or restrictive.

CHAPTER 1:

Strabismus Terminology . 11

Fixation Alternating

Spontaneous alternation of fixation from one eye to the other

Monocular

Definite preference for fixat ion with one eye

Age of Onset A deviation documented before age 6 months. presumably related to a defect present at birth; the term infantile might be more appropriate.

Congenital

A deviation with later onset. after a period of appare ntly normal visual devel -

Acquired opment

Type of Deviation Horizontal Vertical

Esodeviation or exodeviation Hyperdeviation or hypodeviation

Torsional

IncycJodeviation or excyclodeviation

Combined

Horizontal , vertical, torsional, or any combination thereof

Abbreviated Designations for Types of Strabismus The addition of a prime (') to any of the following indicates near fIXation (eg. E' indicates esophoria at near). E. X. RH. LH Esophoria. exophoria. right hyperpho ria. left hyperpho ri a at distance fixa tion. respectively ET. Xl. RHT. LHT Constant esotropia. exotropia. right hypertropia. left hypertropia at distance flXation , respectively EITI. XITI. RH(T). LHITI Intermittent esotropia. exotropia. right hypertropia. left hypertropia at distance fixation. respectively RHoT. LHoT

O. EX = 0

Right hypotropia. left hypotropia at distance fixat ion. respectively Orthophoria (orthoptropia)

Important Axes of the Eye There is occasionally confusion in the ophthalmic literature regard ing terms used to describe the axes of the eye. Following are some important definitions (see also BCSC Section 3. Clinical Optics).

1

12 • Pediatric Ophthalmology and Strabismus Optical axis A line that best approximates the line passing through the optical centers of the cornea, lens, and fovea. Because the lens is usuall y decentered with respect to the cornea and the visual axis, no single li ne ca n precisely pass through each of these points. However, because the amount of decentration is small , the best approximation of this line

is taken to be the optical ax is.

Pupillary axis The imaginary line perpendicular to the corneal surface and passing through the midpoint of the entrance pupil Visual axis

The imaginary line connect in g the fLXation point and the fovea

CHAPTER

2

Anatomy of the Extraocular Muscles and Their Fascia

Origin. Course. Insertion. Innervation. and Action of the Extraocular Muscles There are 7 extraocul ar muscles: the 4 rectus muscles, the 2 oblique muscles, and the levator palpebrae superio ris muscle. Cranial nerve (CN) VI (abdu cens) inn ervates the lateral rectus muscle; CN IV (trochlear), the sup eri or oblique muscle; and CN III (oculomotor), the levator palpebrae. superior rectus, medi al rectus, inferior rectus. and inferior oblique muscles. CN III has an upper and a lower di vision: the upper divisio n supplies the levator palpebrae and superi o r rec tus muscles; the lower di vision supplies the medi al rectus, inferior rectus. and in fe rior oblique muscles. The parasympathetic innervation of the sphincter pupillae and ciliary muscle travels with the bra nch of the lower di vision of CN III that supplies the inferi o r obliq ue muscle. BCSC Sect ion 5, Neuro-Ophthalm ology, discusses the ocular motor nerves in more detail, and Secti on 2, FUlldamentals and Prin ciples of Oph thalmology, extensively illustrates th e anatomical structures mentioned in this chapter. When the eye is directed straight ahead and the head is also straight, the eye is said to be in primary position. The primary action of a muscle is its major effect on the position of the eye when th e muscle contracts while the eye is in primary positio n. The secondary and tertiary act io ns of a muscle are the additional effects o n the positio n of the eye in primary positio n (see also Chapter 3 and Table 3- 1). T he globe usuall y can be moved about 50· in each direction from primary posit ion. Under normal viewing circumstances, however, the eyes move only about 15°_20° from primary posit ion before head movement occurs.

Horizontal Rectus Muscles The hori zontal rectus muscles are the medial and lateral rectus muscles. Both arise from the annulus of ZinnoThe medial rectLis muscle courses along the medi al orbital wall. The proximity of the medial rectus muscle to the medial orbital wall means the medial rectus can be injured du ring ethmoid sin us surge ry. T he lateral rectus muscle courses alo ng the lateral orbital wall. In primary position, the med ial rectus is an adductor, and the lateral rectus is an abductor. The medial rectus muscle is the only rectus muscle that does not have an oblique muscle funnin g tangential to it. This makes surgery on the medial rectus less complicated. but means that there is neither a point of reference if the surgeon becomes disoriented nor a point of attachment if the muscle is lost. 13

14 • Pediatric Ophthalmology and Strabismus Vertical Rectus Muscles The vertical rectus muscles are the superior and inferior rectus muscles. The superior rectus muscle originates from the annulus of Zinn and cou rses anteriorly> upward over the eyeball, and laterally, forming an angle of 23° with the visual axis of the eye in primary position (Fig 2~1; see also Chapter 3, Fig 3~4). In primary position, this muscle's primary action is elevation, secondary action is intorsion (incycloduction), and tertiary action is adduction. The inferior rectus muscle also arises from the annulus ofZinn, and it then courses anteriorly, downward, and laterally along the floor of the orbit, forming an angle of 23° with the visual axis of the eye in primary position (see Chapter 3, Fig 3~5) . In primary position, the inferior rectus muscle's primary action is depression, secondary action is extorsion (excycloduction ), and tertiary action is adduction. Oblique Muscles The superior oblique muscle originates from the orbital apex above the annulus of Zinn and passes anteriorly and upward along the superomedial wall of the orbit. The muscle becomes tendinous before passing through the trochlea, a cartilaginous saddle attached to the frontal bone in the superior nasal orbit. A bursa~like cleft separates the trochlea from the loose fibrovascular sheath surrounding the tendon. The discrete fibers of the tendon telescope as they move through the trochlea, the central fibers moving farther than the

Figure

2-'

The extrinsic muscles of the right eyeball in primary position, seen f rom above.

(Modified with permission from Yano" M. Duker J, eds. Ophthalmology. 2nd ed. London: Mosby; 2004:549.)

CHAPTER 2:

Anatomy of the Extraocular Mu scles and Their Fascia .

15

peripheral ones (Fig 2-2). The function of the troch lea is to red irect the tendon inferiorly, posteriorly, and laterall y, for ming an angle of 5 10 with the visual ax is of the eye in primary position (see Chapter 3, Fig 3-6). The tendon penetrates the Teno n capsule 2 mm nasally and 5 mm posteri o rl y to the nasal insertion of th e superior rectus muscle. PaSSing und er the superior rectus muscle. the tendon inserts in the posterosuperior quadrant of the eyeball , almost or ent irely laterall y to the mid ve rti cal plane or center of rotation. In primary position, the primary action of the superior oblique muscle is intorsion (incycloduction). secondary action is depression . and tertiary action is abdu ction. The inferior oblique muscle originates from the periosteum of the maxillary bone, just posteri or to the orbital rim and lateraJ to the orifice of th e lacrimal fossa. It passes Jaterally, superi orly. and posteri orl y, going inferior to the inferior rectus muscle and insertin g under the lateral rectus muscle in the posterolateral portion of the globe. in the area of the macula. The inferior oblique muscle form s an angle of 5 10 with the visual axis of the eye in primar y position (see Chapter 3, Fig 3-7). In primary position , the muscle's primary action is exto rsion (excycloduction ), secondar y act ion is elevat ion, and te rtiary action is abductio n. Helvesto n EM. The influence of superior oblique anatomy o n fun ctio n and treatme nt. The 1998 Bielsc howsky Lec ture. BitlOwl Vis Strabismus Q. 1999; 14( I): 16- 26.

Levator Palpebrae Superioris Muscle The levator palpebrae superi oris muscle ar ises at the apex of the orbit from the lesser wing of the sphenoid bone just superi or to the annulus of Zinn oThe origin of th is muscle blends with th e su peri or rectus muscle inferiorl y and with the superior oblique muscl e medi all y. The levator pa lpebrae superioris passes anteri o rl y, lying just above th e superior rectus muscle; the fasc ial sheaths of these 2 muscles are connected. T he levator palpebrae

Loose fibrillar, -\\I\~{r ' highfy vascular structure

Cartilage ----"-

l.

A

B

I ~ ·0 ~ I

c[!]

Figure 4-10 The Worth 4-dot test . A. Looking through a pair of red and green goggles, the patient views a box with 4 lights (1 red, 2 green,

1 whitel at 6 m and at 33 em (with the 4 lights mounted on a flashligh t!. The possible responses are given in B to E. 8, Patient sees all 4 lights: peri ph eral fusion with ort hophoria or strabismus with ARC . Depending on ocu lar dominance, the light in the 6 o'clock position is seen as white or pink. C, Pat ient sees 2 red lights : suppression in as. 0, Pat ient sees 3 green lights: suppression in

OD. E. Patient sees 5 lights. The red lights may appea r to the right, as in this figure (uncrossed

dip lopia with esotropia)' or to the left of the green lights (crossed diplopia with exotropia) .

D

~ ~

E

I ~~ ~

--I

(Reproduced wirh permission from von Noorden GK. Campos EC. Binocular Vision and Ocular Motility: Theory and Management of Strabismus. 6th ed. St Louis: Mosby: 2002.221.)

56 • Pediatric Ophthalmology and Strabismus

8agolini glasses Bagolini striated glasses are glasses of no dioptric power that have many narrow striations running para llel in one meridia n. These glasses cause the fixation light to appear as an elongated streak, li ke micro-Maddox cylinders. T he glasses are usually placed at 135· in front of the right eye and at 45· in front of the left eye. The advantages of the Bagolini glasses are that they afford the most lifelike testing conditions and permit the examiner to perfor m cover testing during the exami nation. Figure 4- 11 summ ari zes so me of the

Type of ocular deviation:

Orthophoria

Monofixation syndrome (fixating) OS

Cover Test

No Shift

Small Shift (,;8") or No Shift

Retinal Correspondence

NRC

Peripheral fusion with central suppression (NRC vsARC)

Type of ocular deviation :

Esotropia

Esotropia or Exotropia

Patients perception:

left eye preferred for fixation

OS~ Patient's perception: Cover Test

Large Shift

(>1o,,)

Shift

Retinal Correspondence

ARC with Suppression (larger scotoma than monofixation syndrome)

Suppression

Type of ocular deviation:

Esotropia

Exotropia

Cover Test

Shift

Shift

Retinal Correspondence

NRC with Diplopia No Suppression

NRC with Diplopia No Suppression

(Total) OD

Patient 's perception:

Figure 4-11

Bagolini striated glass test for retinal correspondence and suppression . For these

figures, the Bagolini lens is oriented at 135' in front of the right eye and at 45' in front of the left eye, The perception of the oblique lines seen by each eye under binocular conditions is shown. Examples of the types of strabismus in which t hese respon ses are commonly found are given.

CHA PTER 4,

Se nsory Phys iology and Path olog y .

57

possible subjecti ve res ults of this test. Note that in monofixation syndrome, the central scotoma is perceived as a gap in one of the lines surroundin g the fixati on light. 4,j

base-out prism test

The 4t. base-out prism test is a d iag nostic ma neuver performed primaril y to document the presence of a small fac ultative scotoma in a patient wit h mo nofixati on syndrome and no ma nifest small deviatio n (see the section Mo nofixation Synd ro me later in this chapter). In th is test, a 4t. base-out prism is qu ickly placed befo re I eye and then the other d urin g bin ocular view in g, and moto r respo nses are obse rved (Fig 4- l 2). Patients with bifixation

usuall y show a ve rsion (bilateral) movement away fro m the eye covered by the prism fol lowed by a un il ate ral fusio na l convergence movement of the eye no t behind the prism. A similar response occurs regardless of whic h eye the prism is placed over. Often, no moveme nt is seen in patients with monoftxati o n synd ro me wh en the prism is placed befo re th e nonflx ating eye. A refixatio n version movement is seen whe n th e prism is placed before

the fixati ng eye, but the expected fusional conve rgence does no t occur. T he 4t. base-out prism test is the least rel iable meth od used to doc ument th e presence of a macu lar scotoma. An occasio nal patient with bifixation recogni zes diplo pia when

'f'

Stays abducted

1m

r

00

C Adducts

-

Abducts

.Q> ~

sEe

~ 0

No adduction r --.'----"1 of DO-patient experiences diplopia

Adducts

~

Figure 4-12 The 4~ base-out prism test. A, When a prism is placed over the left eye, dextroversion occurs during refixation of that eye, indicating absence of foveal suppression in the left eye. If a suppression scotoma is present in the left eye, there will be no movement of either

eye when placing the prism before the left eye. B, A subsequent slow fusional adduction movemen t of the right eye is observed, indicating absence of foveal suppression in the right

eye. C, In a second patient, the right eye stays abducted, and the absence of an adduction movement IB) indicates foveal suppression in the right eye. D, Another cause of absence of the adduction movement is weak fusion , and su ch patients experience diplopia until refus ion occurs spontaneously. (Reproduced with permiSSion (rom von Noorden GK, Campos EC. Binocular ViSion and Ocular Motility Theory and Management of Strabismus. 6th ed Sf LOUIS. Mosby; 2002:220.)

58 • Pediatric Ophthalmology and Strabismus

the prism is placed before an eye but makes no convergence movem ent to correct for it. Patients with monofixation syndrome may switch ftxation each time the prism is inserted and show no movement, regardl ess of which eye is tested.

Afterimage test The test can be perfo rm ed by cove rin g a camera flash with black paper and then exposing only a narrow slit, the ce nter of which is covered with blac k tape to se rve as a fixation point, as well as to protect the fovea frolll exposure. Thi s test invo lves the stimulation, or labeling, of the macula of each eye with a different linear afterimage, 1 horizontal and 1 verti cal. Because suppression scotomata extend along the hori zontal retinal meridian and may obscure most of a hori zo ntal afterimage, th e vertical afterimage is placed on the deviating eye and the horizontal afterimage on th e fixating eye sim ply by having each eye fIXate the linear light filam ent separately. The central zone of th e linear light is occluded to allow th e fovea to fixate and remain unlabeled. The patient is th en asked to draw the relative positions of the perceived afterimages. Possible perceptions are shown in Figure 4-13.

Amblyoscope testing Although its use has declined in recent ye ars, the major amblyoscope (Fig 4- 14) in vario us form s (eg, C lement Clarke synoptophore, American Optical troposcope), was for decades a mainstay in the field of strabism us. The amblyoscope ca n be used in the measurem ent of hori zo ntal, ve rtical, and torsional deviations; in the diagnosis of suppression and retin al co rrespo ndence; and in th e dete rmination of fusio nal amplitudes an d the

Patient's view

R-

I I

L _

.

R-

Fovea RE~

LE

-R

LE

RE

LE

RE

EB El9 E9 EB EB EB I

I

I

,

I

I

I

I

I

I L _ _NRC _ _ _ _ ..JI

I

ARC L _____ ..JI

IL _______ ARC ..JI

B

c

A

I,

I

Figure 4·13 Afterimage test. A, Normal localization (cross) in normal correspondence (NRC). B, Anoma lous crossed localization (ARC) in a case of esot ropia. C, Anomalous uncrossed localization in a case of exotropia. (Reproduced with permission from von Noorden GK Campos EC. Binocular Vis ion and Ocular Motility: Theory and Management of St rabismus. 6th ed. St Louis: MosbV; 2002:227.)

CHAPTER 4,

Target slides

Sensory Ph ys iology a nd Pathology. 59

~~

~

~©

_ J ......

UHARC

NRC Patient's view

Patient's view

Patient's view

[0J

~

~

Figure 4·14 Testing with a major amblyoscope for retinal correspondence in a patient with 20 diopters of esotropia. (Reproduced with permission from von Noorden GK, Campos EC. Binocular Vision and Ocular Motility: Theory and Management of Strabismus . 6th ed. Sf LoUIs · Mosby; 2002:229)

degree of stereopsis, with testing usually performed by an orth optist. The major amblyo· sco pe can also be used in exercises designed to overcome suppression and expand fu sional am plitudes. A description of this in strument and its uses can be found in th e following reference. von Noorden G K, Campos EC. Binocular VisiOlI and Ocula r Motility: Theory and M(//wgement a/Strabislllus. 6t h ed. St Louis: Mosby; 2002.

Monofixation Syndrome T he term monofixation syndrome is used to descri be a parti cular presentatio n of a sensory state in strabi smus. The essential featu re of th is synd ro me is th e presence of periph eral fu sion with th e absence of bi mac ul ar fu sion d ue to a phYSiologic macula r scotoma. A patient with mo no Hxation syndrome may have no mani fes t deviation but usually has a small heterotropia (less th an 8t.), most commonl y esotropia. Stereoacui ty is present but reduced. Ambl yopia is a common findin g. The original descri ption of this entity states that reti nal correspondence is norm al regardless of whether there is a manifest deviati o n; this has been questi oned by other auth ors. Mo noHxati on syndrome may be a primary condition. It is a favora ble outcome of in fantil e strab ismus surge ry. This syndrome can also res ult fro m anisometropia or macular lesions. It can be the cause of unilaterally redu ced visio n when no obvious strabismus is present. If amblyopia is clinicall y significant, occlusion therapy is indicated.

Diagnosis To make the d iagnos is of monofixati o n synd rome, the cl inician must demonstrate the absence of bimacular fusio n by documenti ng a mac ular scotoma in th e nonHxating eye

60 • Pediatric Ophthalmology and Strabismus under binocular conditions; and the presence of peripheral binocular vision (per ipheral fusion). Several binocular perimetric techniques have been described to plot the l11onofixation scotoma. However, they are rarely used clinically. Vectographic projections of Snellen letters can be used clinically to document the facultative scotoma of the monofixation syndrome. Snellen letters are viewed through polarized analyzers or goggles equipped with liquid crystal shutters in such a way that some letters are seen with only the right eye, some with only the left eye, and some with both eyes. Patients with monofixation syndrome delete letters that are imaged only in the non fixating eye. Testing stereoacuity is an imp ortant part of the monofixation syndrome evaluation. Any amount of gross stereopsis confirms the presence of peripheral fu sion. Most patients with monofixation syndrome demonstrate 200- 3000 sec of arc stereopsis. However, because some patients with this syndrome have no demonstrable stereopsis, other tests for peripheral fusion , such as the Worth 4-dot test and Bagolini glasses, must be used in conjunction with stereoacuity measurement. Fine stereopsis (better than 67 sec of arc) is present only in patients with bifixat ion. Parks MM . The monofixation syndrome. Trails Am Ophthalmol Soc. 1969;67:609- 657. (This classic thesis outlines early studies of small -angle deviations and central versus peripheral bi nocular vis ion . The development of the various terms used to describe these conditions is also covered in detail.) von Noorden GK, Campos EC. Binoctllar Vision and Ocular Motility: Theory and Management of Strabismus. 6th ed. St Louis: Mosby; 2002:340- 345.

CHAPTER

5

Amblyopia

Amblyop ia is a unilateral

Of ,

less common ly, bilateral reduction of best-corrected visual

acuity that cannot be attributed directl y to the effect of any structural abnormality of the eye or the posterior visual pathways. Ambl yopia is caused

by abnormal visual experience

early in life resulting from one of the following: strabism us anisometropia or high bilate ral refractive e rrors (isomet ropia), stimulus deprivation

Ambl yopia is responsible fo r more unilaterall y reduced vision of childhood o nset than all other causes com bined, with a prevalence of 2%- 4% in the North American population. This fact is particularly distressing because, in principle, most amb lyop ic vision loss is preventable or reve rsibl e w ith tim ely detection and appropriate intervention. Children

with amblyop ia or at risk for am blyopia should be identified at a you ng age, when the prog nos is for sll ccessful treatment is best. Scree ning plays an important role in detecting ambl yopia and other vis ion problems at an early age and can be performed in the primary care practitioner's office, allowing th e primary ca re phys ician to help coordinate the care of these pat ients, or in cornm unity-based vis ion screening programs. Repeated screening

is important for continuing to check for the development of vision problems and is also helpful in detecting false- positive results. A consensus about the best method and the appropriate age to screen has not yet e merged.

Amblyopia is primarily a defect of central vision; the peripheral visual field is usually normal. Experimental studi es on animals and clinica l studies of infants an d young

children support the concept of criti cal periods for sensitivity in developing amb lyopia. These critical periods correspond to th e period when the ch ild's developing visual system is sensitive to abnormal inpu t caused by stimulu s deprivation, strabismus, or Significant refract ive e rrors. In general , th e critica l period for stimulus deprivation amblyopia occurs earl ier than th at for ocular misalignment or anisometropia. Furthermore, th e time necessary for amblyopia to occur during the cr itica l period is shorter for sti mulu s deprivation than for strabismus or anisometropia.

Although the neurophys iologic mechanisms that underlie amblyopia are far from clear, the study of experimenta l mod ifi catio n of visual experience in animals and labo-

ratory testing of humans with amblyopia have provided some inSights. Animal models have revea led that a variety of profoun d disturban ces of visual system neuron function may result fro m abnormal early vis ual expe ri ence. Cell s of the pri mary visual cortex can

completely lose their innate ability to respond to stimulat ion of I or both eyes, and cells 61

62 • Pediatric Ophthalmology and Strabismus that remain responsive may show significant functional deficiencies. Abnormalities also occur in neurons in th e lateral geniculate body. Evidence concerning involvement at the retinal level remains inconclusive; if present, changes in the retina make at most a minor contributi on to the overall visua l defect. Several findings from both animals and humans, such as in creased spatial summati on

and lateral inhibition when light detection thresholds are measured using different-sized spots, suggest that the receptive fields of neurons in the amblyopic visual system are abnormally large. This disturbance may account for the cro wding phenomenon (also known as contour interaction), whereby Snell en letters or equivalent symbols of a given size be-

come more difficult to recognize if they are closely surrounded by similar forms, such as a full line or field of letters. Daw NW. Critical periods and amblyopia. Arch Ophthafmol. 1998; 11 6(4):502-505 . Simons K. Preschool vision screening: rationale, methodology, and outcome. 511rv Ophtlwlmol. 1996;41 ( I );3- 30. von Noorden GK. Amblyopia: a multidisciplinary approach. Proctor lecture. 1I1ves! OphthalniDI

Vi,Sci.

1985;26(12);1704- 1716.

Classification Amblyopia has traditionally been subdivided in terms of the major disorders that may be responsibl e for its occurrence.

Strabismic Amblyopia The most common form of amblyop ia develops in the consistently deviating eye of a ch ild with strabismus. Constant, non alternating heterotropias (typicall y esodeviations) are most likely to cause Sign ificant amblyopia. Strabismic amblyopia is thought to resu lt fro m compet itive or inhibitory interaction between neurons carrying the nonfusibl e inputs from the 2 eye~, which leads to domination of cor tica l vis ion centers by th e fixating

eye and chronicall y reduced responsiveness to input by the non fi xating eye. Amblyopia itself does not as a rule prevent diplopia. Older patients with long-standing deviations might develop double vision after strabismus surge ry despite the presence of substantially reduced visual acuity from am blyopia. Several features of typica l strabismic amblyop ia are uncommon in other forms of am -

blyopia. In strabismic amblyopia, grating acuity, the ability to detect patterns composed of uni formly spaced stripes, is often reduced considerab ly less than Snellen acuity. Apparently, the affected eye sees forms in a tw isted or distorted manner that in terferes more

with letter recognition than wi th the simpler task of determining whether a grating pattern is present. This discrepancy must be considered when the results of tests based on grating detection, such as Teller card preferential looki ng (a method of estimating acuity in infants and toddle rs), are interpreted (Fig 5- I). When visual acuity is checked with the use of a neutral-density filter, the acuity of an eye with amblyopia tends to decline less sharply than that of a normal eye. This phenomenon is called the neutral-density filter effect.

CHAPTER 5,

Figure 5-1

Am blyo pia .

Teller acuity card being used to measure the visual acuity in a preverbal child.

63

(Cour-

tesy of John W. Simon, MD.J

Eccentric fixa tion refe rs to th e consistent li se of a Il o nfoveal regio n of th e re tin a for mo nocular viewin g by an ambl yopic eye. Min o r degrees of eccentric fixati o n, de tectable o nly with specia l tests such as ViSlISCOp y, are seen in many pat ients with st rab ism ic am blyo pia and relat ively mild acu ity loss. A visuscope projects a target with an open center surrounded

by

2 concentri c circles on to the re tina, and the pati ent is asked to fixate on

the target. If the target is not di rected at the fovea, the degree of eccentri c fixat ion can be measured lIsing the concentric ci rcles as a guide. Ma ny ophth alJll oscopes are equi pped

with a visuscope. Cli nically evident eccent ric fi xati on, detectable by obserVing the no ncentral positio n of the corn eal refl ectio n fro m the amb lyopic eye while it fixates a light with the dominant eye covered, ge nerall y impli es visual acui ty of 20/200 or wo rse. See Chapte r 6 fo r a discussion o f clin ica l testin g. Use of th e nonfoveal re tin a fo r fixati o n cannot, in ge neral, be regard ed as th e primar y cause of reduced ac uity in affec ted eyes. The mechanis m of thi s interes tin g phe no me non, long a source of spec ulation, rema ins un kn own.

Anisometropic Amblyopia Second in frequency to strabism ic am bl yo pia, anisometropic am bl yopia develops when unequal refrac ti ve errors in th e 2 eyes causes the im age on 1 ret in a to be c hron ica lly de-

focused. T his condition is th ought to result partly from the direct effect of image blur on visua l ac uity development in th e invo lved eye and partl y from interocul ar compet iti on o r inh ibiti on similar (but not necessaril y id e ntical) to th at responsible fo r strabism ic am -

blyopia. Relati vely mild degrees of hyperopic o r astigmatic anisometropia (1-2 0) can in du ce mild amblyopia. Mild myopic anisometropi a (less th an -3 0 ) usuall y does not cause am blyo pia, but unilateral high myop ia (- 6 0 or greater) often res ults in severe amb lyopic visio n loss. Unless strabismus is present, the eyes of a chi ld with an isometrop ic ambl yo pia

look normal to the family and primary care physicia n, typicall y causing a delay in detection and treatme nt.

64 • Pediatric Ophthalmology and Strabismus

Ametropic Amblyopia Ametropic amblyopia, a bilateral reduction in acuity that is usually relatively mild, results from large, approximately equal, uncorrected refractive errors in both eyes of a young child. Its mechanism involves the effect of blurred retinal images alone. Hyperopia exceeding about 5 0 and myopia in excess of 6 0 carry a risk of ind ucing bilateral amblyopia. Uncorrected bilateral astigmatism in early childhood may result in loss of resolving ability limited to the chronically blurred meridians (meridional amblyopia). The degree of cylindrica l ametropia necessary to produce meridional amblyopia is not known, but 1110st ophthalmologists recommend correction of greater than 2 D of cylinder.

Stimulus Deprivation Amblyopia Deprivation amblyopia may occur when the visual axis is obstructed. The 1110St common cause is a congenital or early acquired cataract, but corneal opacities and vitreo us hemorrhage may also be implicated. Deprivation amblyopia is the least common but most damaging and difficult to treat of the various forms of amblyopia. Amblyopic vision loss resulting from a unilateral occlusion of the visual axis tends to be worse than that produced by bilateral deprivation of similar degree because interocular effects add to the direct developmental impact of severe image degradation. Even in bilateral cases, however, acuity can be 20/200 or worse. In ch ildren younger than 6 years, dense congenital cataracts that occupy the central 3 mm or more of the lens must be considered capable of caus in g severe amblyopia. Similar lens opacities acquired after age 6 years are generally less harmful. Small polar cataracts, around which retinoscopy can be readily performed, and lamellar cataracts, through which a reasonably good view of the fundus can be obtained, may cause mild to moderate amblyopia or may have no effect on visual development. Occlusion amblyopia is a form of deprivation amblyopia that may be seen after therapeutic patching.

Diagnosis Amblyopia is diagnosed when a patient is found to have a condition known to in crease the risk of amblyopia and when reduced visual acuity cannot be explained entirely on the basis of physical abnormalities of the eye. Characteri stics of vision alone cannot be used to reliably differentiate amblyopia from other forms of vision loss. The crowding phenomenon, for example, is typical of amblyopia but is not pathognomonic or uniformly demonstrable. Afferent pupillary defects rarely occur in amblyopia, and th en, only in severe cases. Amblyopia sometimes coexists with vision loss directly caused by an uncorrectable structural abnormality of the eye such as optic nerve hypoplasia or coloboma. When the clinician encounters doubtful or borderline cases of this type ("organic amblyop ia") in a young child, it is appropriate to undertake a trial of occlusion therapy. Improvement in vision confirms that amblyopia was indeed present. Multiple assessments using a variety of tests or performed on different occasions are sometimes required to make a final judgment concern ing the presence and severity of amblyopia. General techniques for visual acuity assessment in children are discussed in

CHAPTER 5:

Amb lyop ia . 65

Chapter 6, but the cl inician trying to determine the degree of amblyopic vision loss in a young patient should keep certain special considerations in mind. The fixation pattern, which indicates the strength of preference for 1 eye or the other under binocular viewing conditions, is a test for esti mating the relative level of vision in the 2 eyes for preverbal children with strabismus. Th is test is qu ite sensitive for detectin g amb lyop ia, but results can be falsely positive, showin g a strong pre fe rence whe n vision is equa l or nearly equal in the 2 eyes, pa rticularl y with small -angle strabismus. A variety of optotypes can be used to di rectly measure acuity in children 3-6 years old. When possible, it is best to use linear symbols to measure visual acuity. Often, however, only isolated symbols can be used, which may lead to underestimated amblyopic vision loss d ue to the crowding phenomeno n. Crowding bars help alleviate th is problem (Fig 5-2). In additio n, the you ng child's brief attention span frequently results in measurements that fall short of the true limits of acuity; these results can mimic bilatera l amblyopia or obscure or fa lsely suggest a Significant interoc ular difference.

Treatment Treatment of amblyopia involves the fo llowing steps: 1. Eliminate (if needed) any obstacle to visio n, such as a cataract. 2. Correct any sig ni ficant refractive error. 3. Force use of the poorer eye by limiting use of the better eye.

Cataract Removal Cataracts capable of producing amb lyo pia requ ire surgery wi th out unn ecessary de lay. In yo un g children, amblyopia may develop as qUickly as 1 week per age of life. Removal of Visua ll y Significant conge ni ta l lens opacities during th e fi rst 4-6 weeks of li fe is necessary for optima l recovery of vis ion. In symmetric bilateral cases, the interval between operations o n the fi rst and second eyes should be no more tha n 1- 2 weeks. Ac utel y developing severe tra umatic cataracts in chi ldren yo unger than 6 years should be removed with in a few \veeks of injur y, if possible. Signi ficant cataracts with uncertain tirn e of onset also deserve prompt and agg ressive treatment during childhood if recent development is at least a possibili ty (eg, in the case of an opacity that appears to have origi nated fro m a posterior

---

---

---

IIEII

11011 ---

Figure 5-2 Crowding bars, or con tour interaction bars, allow the examiner to test crowding phenomenon w ith isolated optotypes. Bars surrounding the optotype mimic the full row of optotypes to the amblyopic child. {Reproduced With permission from Coars OK, Jenkms RH. Vision assessment of the pediatric patient. Refinemen ts. San Francisco: American Academy of Ophthalmology; 1997,1: 1.'

66 • Pediatric Ophthalmology and Strabismus lenticonus deformity). Chapter 21 of this volume and BCSC Section 11 , Lells alld Cataract, discuss the special considerations of cataract surgery in children.

Refractive Correction In general, optical prescription for amblyopic eyes shou ld be based on the refractive error as determined with cycloplegia. Because an amblyopic eye's ability to control accommodation tends to be impaired, this eye cannot be relied o n to compensate for uncorrected hyperopia as would a normal child's eye. Sometimes, however, symmetric decreases in

plus lens power may be req uired to foster acceptance of spectacle wear by a child. Refractive correction for aphakia fo llowing cataract surgery in childhood must be provided promptly to avoid compounding the visual deprivation effect of the lens opacity with that of a severe optical deficit. Both anisometropic and ametropic amblyopia may improve or resolve with refractive correction alone over several 1110nths. Give n thi s, many ophthal mologists wait to initiate patching or penali zation (d iscussed in the following section) in order to see whether the vision improves with spectacle correction alone. The role of refractive surgery in those patients who fail conventiona l treatment with spectacle s and/or contact lenses is under investigation. Cotter SA; Pediatric Eye Disease Investigator Group. Treatment of anisometropic amblyopia in children wi th refractive correction. Ophtlwllllology. 2006; 11 3(6):895-903. Paysse EA. Photorefractive keratectomy for anisometropic amblyopia in childre n. Trails AII1

Oplltllallllol Soc. 2004; 102:341 -37 1.

Occlusion and Optical Oegradation Full-time occlusion of the so un d eye is defined as occlusion during all waking ho urs. This treatment is usual ly performed usin g com mercially ava ilab le ad hes ive patches. Spectacle· mounted occluders or special opaque contact lenses can be used as an alternative to fu ll · time patching if skin irritat ion or inadequate adhesion is a significant problem. provided that close supervis iQn ensures that the spectacles rema in in place conSistently. (Switching

to a different brand of patch or preparing the skin with tincture of benzoin or ostomy adhesive before application can eliminate most skin-related problems.) Rarely, strabismus may result during full -time patching; it is not known whether strabismus would have occurred with other forms of amblyopia treatment. Therefore, the child whose eyes are consistently or intermittently straight may benefit by being given some opportunity to see binocularly. Modest reductions in patching are employed by many ophthalmologists (removing the patch for an hour or two a day) to reduce the li keli hood of occl usion am blyopia or of inducing strabismus. Parl-till1e occlusion, defined as occlusion fo r 2-6 hours per day, has been shown to ach ieve the same results as the prescription of flill ·ti me occlusion. The relative duration of

patch-on and patch-off intervals should reflect the degree of amblyopia; for moderate to severe defic its, at least 6 hours per day is preferred. Compliance with occlusion therapy for ambl yop ia decl ines with increasing age. The effectiveness of more acceptable part-time patching regimens in older children is being actively investigated. Furthermore, studies in older children with amblyopia have shown

CHAPTER 5,

Amblyopia.

67

that treatment can still be beneficial beyond the first decade of life. This is especially true in children who have not previously undergone treatment. Other methods of amb lyop ia treatment involve optical degradation of the better eye's image to the point that it becomes inferior to the amblyopic eye's, an approach often called penalization. Use of the amblyopic eye is thus promoted within the context of binocular seeing. Studi es have demonstrated that pharmacologic penalization can be used to successfull y treat moderate levels of am blyopia. The improvement in vision has been shown to be similar to that obtained with the prescription of patching. A cycloplegic agent (usuall y atrop ine .1% drops or homatropine 5% drops) is administered to the better-seeing eye so that it is unable to accom modate. As a result, the better eye experiences blur with near viewing and, if uncorrected hyperopia is present) with distance viewing. This form of treatment has been demonstrated to be as effective as patching for mild to moderate amb lyopia (visual acu ity of 201100 o r better in the amblyopic eye) . Depending o n the depth of amblyop ia and the response to prior treatment, the hyperopic correction of the dominant eye can be red uced to enhance the effect. Regular follow-up of patients whose amblyopia is bei ng treated with cycloplegia is important to avoid rev.,..se am blyopia in the previously preferred eye, alt hough th is is very rare with penalization. Pharmacologic penalization offers the parti cular advantage of being difficult to thwart even if the child objects. Alternative met hods of treatment based on the same principle involve prescribing excessive plus-power lenses (fogging) or di ffuS ing filters. These methods avoid potential pharmacologic side effects and may be capable of ind UCing g reater blur. If the ch ild is wearing glasses, application of translucent tape or a Bangerter foil (a neut ra l-density filter) to the spectacle lens can be tried. Proper utilization (no peeking!) of spectacle-borne devices lllu st be closely mon itored. Another benefit of pha rmacologic penalization and other nonocclud ing methods in patients with stra ight eyes is that the eyes can work together, a great practical advantage in children with late nt nystag mus. Pediatric Eye Disease Investigator Group. A rand omized trial of atropine vs. patchi ng fo r treat ment of moderate amblyopia in ch ildren. Arch Ophtlwllllol. 2002; 120(3):268- 278. Scheiman MM, Hertle RW, Beck RW, et al. Rundomized tria l of treatment of amblyopia in ch ildre n aged 7 to 17 years. Arch Ophlhalmol. 2005: 123(4}:437-447.

Complications of Therapy Any form of amblyopia therapy introd uces the possibility of overtreatment leading to amblyopia in the originall y better eye. Full -time occl usion carri es the greatest risk of this comp li cation and requires close mon itoring, espec iall y in the yo unger ch il d . The first fo llow-up visit after in it iation of trea tment should occur within I week for an in fant and after an interval correspond ing to I week per year of age for the older child (eg, 4 weeks for a 4-year-old). Subsequent visits can be schedul ed at longer intervals based on early response. Part-time occlusion and optical degradation methods aLlow for less frequent observation, but regu lar fo llow-up is still critical. T he parents of a strabismic child should be instructed to watch for a switch in flXation preference and to report its occurrence promptly. Iatrogenic amb lyopia can usuaLly be treated successfull y with judicious patching

68 • Pediatric Ophthalmology and Strabismus of the better-seeing eye or by alternating occlusion. Sometimes, simply stopping treatment altogether for a few weeks leads to equali zation of vision.

The desired endpoint of the rapy for unilateral amblyopia is free alternation of fixation (although I eye may still be used somewhat more frequentl y than the other), linear Snellen acuity that differs by no more than I line between the 2 eyes, or both. The time required fo r completion of treatment depends on the following: degree of amblyo pia choice of therapeutic approach compliance wit h the prescribed regimen

age of the patient More severe amblyopia, less complete obstruction of th e dominant eye's vision, and

older age are all associated with a need for more prolonged treatment. Full-time occlusion during infan cy may reverse substantial strab ism ic amblyopia in 1 week or less. In contrast, an older child who wears a patch onl y after school and on weekends may require a year or more of treatment to overcome a moderate deficit.

Compliance issues Lack of compliance with the therapeutic regimen is a common problem that can prolong the period of treatment or lead to outright fa ilure. If difficulties derive from a particular treatment method, a suitable alternative should be sought. Families who appea r to lack sufficient moti vatio n should be counseled concerning the importance of th e project and the need for firmness in carrying it out. They can be reassured th at once an appropriate

routine is established and maintained for a short time, the dail y effort required is li kely to diminish, especially if the am blyopia improves. T he problems associated wi th an unusually resistant child vary acco rding to age. In infancy, restraining the child through physical methods such as arm splints or mittens or merely making the patch more adhesive with tin cture of benzoin may be useful. For

children older than 3 years, creating goals and offering rewards tends to work well, as does linking patching to play activities (eg, decorating the patch each day or patching while the child plays a video game). Authoritative words d irected speCificall y toward the child by the doctor may also help. The toddler period (J -3 years) is particularly challenging.

Unresponsiveness In some cases, even conscient ious application of an appropriate therapeutic program fails to improve vision at all or beyond a certain level. Complete or partial unrespons iveness to treatment occaSionally affects younger children but most often occurs in patients older than 5 years. The decision of whether to ini tiate or continue treatment in a prognosticall y

unfavorable situati on should take into account the wishes of the patient and family. Primary therapy should generally be terminated if there is a lack of demonstrable progress over 3-6 months with good compliance.

Before it is concluded that intractable amblyopia is present, refraction should be rechecked, the pupils carefully reevaluated, and the macula and optic nerve criticall y in spected for subtle evidence of hypoplasia or other malformation that might have been

CHAPTER 5,

Amblyopia'

69

previously overlooked. Neuroimaging might be considered in cases that inexplicably fail to respond to treatment. Amblyopia associated with unilateral high myopia and extensive myelination of retinal nerve fibers is a specific syndrome in which treatme nt failure is part icularly common.

Recurrence When amblyopia treatment is discontinued after full y or partially successful completion, approximately 25% of patients show some degree of recurrence, which can usually be reversed with renewed therapeutic effort. Institution of a maintenance regimen such as

patching for 1-3 hours per day, optical penalization with spectacles, or pharmacologic penalization with atropine 1 or 2 days per week can prevent backsliding. If the need for maintenance treatment is established, treatment must be cont inu ed until stab ility of visual acuity is demonstrated with no treatment other than regular spectacles. This may require periodic monitoring until age 8- 10 years. As long as vision remains stable, intervals of up to 6 months between follow-up visits are acceptable. The improvement in visual acu ity

that is obtained in most children treated between 7 and 12 years of age is sllstained following cessation of treatment.

.

CHAPTER

6

Diagnostic Techniques for Strabismus and Amblyopia

History and Characteristics of the Presenting Complaint When the patient is a child, it is especiall y important to obtain information regarding the moth er's pregnancy, pay ing close attent ion to ma ternal hea lth , gestational age at th e time

of birth, birth weight, and neonatal histor y. The physician should also' ask about the child's developme ntal m ilesto nes.

It is desirable to document the age of onset of a deviation or symptom. Old photographs may be useful for this purpose. In add ition, the physician should seek to answer the following questions about the deviation or symptom: Did its onset co in cide wit h trauma or illn ess? Is th e deviati on consta nt or in termi ttent? Is it present fo r dista nce or near vision or both ?

Is it un il ateral or alternating? Is it present only when the patient is inattentive or fati gued ? Does the chi ld close I eye? Is the dev iati o n associated with do uble visio n o r eye strain?

Earlier treatment should be reviewed, such as amblyo pia therapy, spectacle correction, use of miotics, orthoptic therapy, or prior eye muscle surge ry. While obtaining the history, the physician should observe the patient continuall y, noting such behaviors as head postu ring. head movement, attentiveness, and motor control.

Past and present medications should be recorded, along with drug sensitivities and allergic responses. Any history of thyroid or neurologic problems should be particularly emphasized. It is also important to document anestheti c methods used fo r previous surgeries and

any related problems, and a detailed fam ily history of strabismus or other eye disorders.

Assessment of Visual Acuity Distance Visual Acuity Several tes ts are ava ilabl e for distance visual acuity determination. The sys te m used to

measure vision should be properly calibrated for the test distance to be utilized. Table 6-1 lists the ex pected ac uity for various tests at different ages. 71

72 • Pediatric Ophthalmology and Strabismus Table 6·' Normal Visual Acuity Using Various Tests in Children Age (Years)

Vision Test

Normal

0-2 0-2 0-2 2-5 2-5 2-5 5+

Visua lly evoked potentia l (VEP)

20/30 lage 11 20/30 lage 21

Preferential looking Fi xation behavior Alle n pictures HOTV E~game

S nellen

CSM (see text )

20/40-20/20 20/40-20/20 20/40-20/20 20/30-20/20

By convention, visual acuity is determined first for the right eye and then for the left. A patch or occluder is used in front of the left eye as the acuity of the right eye is checked, then vice versa. An ad hes ive patch is the most effect ive occluder. The lin e with th e small -

est figures in which the majo rity ofletters can be read accurately is recorded; if the patient misses a few of the figures on a lin e, a notation is made. If the patient does not have corrective lenses, a pinhole may be used to est im ate the best visual acuity potential. Patients with poor vision may need to wa lk to th e chart until they can see the 20/400 lin e. In such cases, visual acu ity is record ed as the distan ce in feet (n umerator) over th e

size of the letter (de no minator); for example, if the patient is able to read the big E at 5 ft, the acuity would be recorded as 5/400. Because the select ion of large figures is limited, it is advisable to confi rm measurements slightl y closer to th e chart usin g figures that can be

changed. Visual acuity assessment of children is often difficult, and the clinician must resort to various means of eva lu ati o n. 1n preverbal or no nverbal children, acuity ca n be eva lu ated

by the CSM m eth od. C refers to the locatio n of the corneal light refl ex as the patient fixates the examiner's light under monocular conditio ns (opposite eye covered). Normall y, the reflected ligh t from the cor nea is near th e center o f the corn ea, and it should be positioned symmetrically in both eyes. Jfthe fi xatio n target is viewed eccentrically, fixation is termed

"ncentral (UC). S refers to the steadiness of fixation on the exami ner's light as it is held motionless and as it is slowly moved about. The S evaluati on is also done under monOClIlar condition s. M refers to the ability of the strabisrnic patient to maintain alignm ent fi rst with I eye, then with the o ther, as the opposite eye is uncovered. Maintenance of fixatio n is eva luated under binocu lar cond itions. Inability to maintain fixation with eith er eye wi th the opposite eye uncovered is presumpti ve evidence of a difference in acuity between the 2 eyes. Thus, preverbal or nonverbal patients with stron g fixation preference in J eye sho ul d

be suspected of hav ing am blyo pia in the other eye. An eye that has eccentric fixation and nystagmoid movements vvhen attempt in g fixat ion would have its visual acu ity des ignated

uncentral, unsteady, and unmaintained (UC, US, UM). In a child with st rai ght eyes, it is impossible to tell whether he or she wil l main ta in fi xation with either eye unless the induced tropia test is used. This test is performed by placing a base-verti cal prism of 10-15 prism diopters (~) over I eye to induce aver· tical deviation. An alternative method involves holding a prism with base in to in duce

CHAPTER 6:

Diagnostic Techniques for Strabismus and Amblyopia.

73

esotropia. The patient is then tested for the ability to maintain fixation with either eye under binocular, albeit dissociated, viewing conditions. It is also important to determine whether each eye can maintain fixation through smooth pursuit or a blink; strong fixation preference for 1 eye indicates amblyopia in the non preferred eye. Occasionally, avo idance movements can be demonstrated when the good eye is occluded. The pat ient may attempt to maneuver around the occluder when the good eye is occluded but not when the poorly seeing eye is covered. A child with poor vision in the right eye, for example, might be noted to " fIX and follow" (F and F) more poorly using that eye and to object to occlusion of the left eye. The visual acuity of preschool-aged and older children can be tested using the illiterate E test (the E-game), letters, numbers, or symbols, all generically referred to as optotypes. Ch ildren being tested with the E-game are asked to point their hand or fingers in the direction of the E. This test can be difficult to use because of developmental status and confusion of right versus left even among children with good acuity. Visual acuity testing with Snellen letters or numbers requires the child to narne each letter or number, whereas visual acuity testing with the HOTV test or with LEA symbols can be done by matching, a cognitively easier task. Whenever possible, a line of optotypes or single optotypes surrounded by contour interaction bars ("crowding bars") should be used to prevent the overest imation of visual acuity of an amblyopic eye that often occurs with isolated optotypes (see Chapter 5, Fig 5-2). Isolated optotypes sho uld be used only if the ch ild cannot be tested with any other class of optotype; Allen pictures do not provide any contour interaction, and thei r overall size and th e width of their und erlyi ng components fail to conform to accepted parameters of optotype design. In addition to recording th e resuits, the clinician should identify the type of test used in order to facilitate com parisons with measurements taken at other times. Most pediatric ophthalmologists consider Snellen acuity most reliable, followed by HOTV, LEA symbols, the illiterate E test, Allen pictures, and fixation behavior. The most reliable test that the child can perform should be used. Preferential looking techniques using Teller acuity cards can be a useful adjunctive test for comparing visual ac uity between fellow eyes in infants and preverbal children. The Ca rdiff Acuity Test, which uses vanishing optotypes and preferential looking techniques, is popular in Europe. LogMAR testing is becom ing more popular. LogMAR is expressed as the logarithm of the minimum angle of resolution and converts the geome tric sequence of a traditional test chart to a linear scale. The use of LogMAR allows more effective analysis of visua l acuity scores and more precise comparisons of results. This system is often used clinically in the Cardiff test and in research protocols. Patients with latent nystagmus may show better visual acuity with both eyes together than with 1 eye occluded. To assess distance monocular visual ac uity in this situation , it is helpful to fog the eye not being tested with a lens that is +5 D greater than the refractive error in that eye. Wright KW, Walonker F, Edelman P. lO -Diopter fixation test for amblyopia. Arch Ophtha/mol. 1981;99(7H242- 1246.

74 • Pediatric Ophthalmol ogy and Strabi smus

Near Visual Acuity Uncorrected and correc ted near visual acuity are determined, again using age- appropriate symbols. Because of inaccuracy related to view ing distance, near visual ac uities should never be compared with distance acuities in children. A measurement of near visual acu-

ity in child re n with reduced vision is im portant in helping determine how they fun ction at school.

Assessment of Ocular Alignment Ocular alignment tests can be grouped into 4 basic types: cover tests, corneal light reflex tes ts, dissimilar image tests, and dissimilar target tests.

Cover Tests Eye movement capab ili ty, image fo rma ti o n and perceptio n. foveal fLXati on in each eye, attentio n, and cooperati on are all necessities fo r cover testi ng. If a pati ent is unable to maintain constant fi xation on an accommo dati ve target, the results of cover testin g may

not be valid, and this batter y of tests therefore should not be used. There are 3 types of cover tests: th e cover-uncover test, th e alternate cover test, and th e simuJtaneous prism and cover test. All can be performed with fix ation at distance or near. The monocul ar cover- uncover test is the most important test fo r detectin g the presence o f manifest strabismus and fo r di fferentia ti ng a heterophoria from a heterotropia

(Fig 6-1) . As I eye is covered, the exa miner watches carefull y fo r an y movement in the opposite, nOl1covered eye; such movement indi cates th e presence of a heterotropia. With movement o f th e noncovered eye assumed to be absent, movement of th e covered eye in one direction just after th e cover is applied and a movement in th e opposite direction (a fu sional move ment ) as the cover is removed indicate a heterophoria that becomes mani -

fest only when binocularity is interrupted. If the patient has a hetero phoria, the eyes will be straight before and after the cove r-uncover test; the deviation that appea rs during the test is a result of interrupt ion o f bin ocular vision. A patient with a heterotropia. howeve r,

starts out wi th a deviated eye and ends up (after the test) with either the same or the opposite eye deviated (if the opposite eye is the deviated one, the condition is termed altern ating heterotropia). Some patients may have straight eyes and start out with a heterophoria prior to the cover-uncover test; however, after prolonged testing- and therefore prolonged interruptio n of binocular vision - dissociatio n into a manifes t heterotropia can occur. The alternate cover test (prism an d cover test) measures the total deviation, regardless

of whether it is latent or manifest (Fig 6-2). This test does not specify how much of each type of deviation is present (ie, it does not separate the heterophoria fro m the heterotropia). This test should be done at both distance and near fIXation. Once dissociation is achieved, the amount of deviation is measured using prisms to eliminate the eye movement as the cover is alternately switched from eye to eye. It may be necessary to use both

horizontall y and ve rtically placed prisms. The amount of prism power required is the measure of deviation. Two horizontal o r 2 vertical prisms shou ld not be superimposed on each other because th is can induce significant measurement errors. Their values cannot

CHAPTER 6:

Diag nostic Techniques for Strabism us and Amb lyopia .

75

Examine Corneal Light Reflexes

If equal, no strabismus but may have heterophoria.

If unequal, heterotropia exists.

@ @

@ @ os

OD

os

OD

To test for heterophoria, cove r 00 (aS will not move).

To prove heterotropia, cover fixating eye (00) ; remaining eye (OS) wi ll move to pick up fixation , proving heterotropia.

--

@

OD

When cover removed (from 00). I

----

@ os

os OD

OD

--

os

00 moves to recover fixation, proving heterophoria.

When cover removed (from 0 0 ). I

os

OD

If 00 does not have to move to recover fixation, there is no heterophoria .

as. as

OD

os

Neither eye moves, but fixation now alternated , proving no amblyopia.

Repeat, covering and uncovering should move only when uncovered to prove heterophoria. Figure 6-1

os

---- ---OD

Both eyes shift with corneal reflexes same as beginning. Probable amblyopia

as.

The monocular cover-uncover test.

be direc tl y added. A more acc urate method for measuring large deviat ions is to place prisms in fro nt of each eye, although it should be noted that these are not perfectly add itive either. However, it is acceptable to superim pose a horizontal prism on a vertical prism before the same eye if necessary. Whereas th e alternate cover test measures th e total dev iation (hete rophoria and heterotro pia), the simultaneous prism and cover test is helpful in de termining the actual heterotropia when both eyes are uncovered (heterotropia alone). The test is perfor med by covering the fIxating eye at the same time the prism is placed in front of the deviating eye. The test is repeated using increasing prism powers un til the dev iated eye no longer shi fts. This test has special application in mo nofixation syndrome, which may include a small -angle heterotropia. Patie nts with this condit ion may reduce the amount of deviation measu red in th e alte rnate cover test by exerti ng at least partia l control over a coexisting

76 • Pediatric Ophthalmology and Strabismus Light

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