OKAP REVIEW OF PEDIATRIC OPHTHALMOLOGY AND STRABISMUS April 1. 2008

OKAP REVIEW OF PEDIATRIC OPHTHALMOLOGY AND STRABISMUS April 1. 2008 DEVELOPMENT OF VISION THE SENSORY SYSTEM AMBLYOPIA ANATOMY OF THE EXTRAOCULAR MUSCLES Lisabeth S. Hall, M.D. Director Pediatric Ophthalmology and Strabismus New York Eye and Ear Infirmary New York NY 10003 (212) 979-4614

OKAP REVIEW OF PEDIATRIC OPHTHALMOLOGY AND STRABISMUS OUTLINE 1. Sensory physiology and pathology A. Development of normal binocular vision 1) Normal retinal correspondance 2) Vieth-Muller circle 3) Empirical horopter 4) Fusion 5) Stereopsis B. Pathology of sensory function C. Abnormal Retinal Correspondance D. Diplopia 1) Physiologic diplopia 2) Confusion E. Supression F. Monofixation syndrome G. Tests of sensory anomalies 1) Worth four dot 2) Bagolini test 3) Afterimage test 4) Synoptophore 5) Amblyoscope 6) Titmus test 2. Development of the visual system A. B. C. D. 3. Anatomy of the extraocular muscles A. B. C. D. E. F. 4. Amblyopia Assessment of amblyopia Treatment of ablyopia Eccentric fixation Origin Course Insertion Action Vascular supply Orbital and facial relationships 1) Lockwoods ligament Summary

OKAP REVIEW 2008 Lisabeth S. Hall, MD Director Pediatric Ophthalmology and Strabismus Pediatric Ophthalmology and Strabismus II. Sensory anomalies I. Development of the visual system OKAP REVIEW 2008 OKAP REVIEW 2008 Pediatric Ophthalmology and Strabismus Pediatric Ophthalmology and Strabismus III. Amblyopia IV. Anatomy of the EOM’s Summary, review and quiz Sensory system FORM OKAP REVIEW 2008 Pediatric Ophthalmology and Strabismus Sensory system COLOR Sensory system Sensory system Motor system LOCATION visual space Sensorimotor system ¾ visual sensations precipitate a chain of motor responses that move the eyes 1

Visual development Vision requires: Neurophysiology Anterior visual system Visual development Vision requires: ¾ stimulus 1) intact optical system 3) synapses with feedback 2) photo-pigment-mediated transformation 4) precise binocular mapping of the environment onto the retina, lateral geniculate body and occipital cortex of light into wave action potentials Neurophysiology Lateral Geniculate Body received by retinal photoreceptors ¾ optic nerve ¾ optic tract ¾ optic chiasm Neurophysiology Lateral Geniculate Body Neurophysiology Lateral Geniculate Body ¾ ¾ ¾ LGN or LGB thalamus ¾ ¾ ¾ Lateral Geniculate Body receives afferent fibers from the anterior visual pathway relays information to primary visual cortex mechanism unknown organized in 6 layers 6 - outermost 1 - innermost uncrossed, ipsilateral - 2, 3, 5 crossed, contralateral - 1, 4 6 Vision Neurophysiology - LGN Neurophysiology - LGN ¾ important ¾ must clinically know for BOARDS: 2 cell types: Magno-large Parvo - small P cells M CELLS WHERE WHAT parafoveal, peripheral color, two point discrimination Magnacellular neurons Parvocellular neurons 2

Neurophysiology Occipital lobe Development of normal binocular vision Visual space ¾ Objective ¾ also called: striate cortex Brodman’s area 17 ¾ must understand concepts of objects in physical space outside of and independent of our visual system ¾ Subjective visual space conscious awareness of objects and perception by our brain visual direction Development of normal binocular vision Visual direction Retinal correspondence ¾ normally ¾ stimulation of any retinal area results in visual sensation from a subjective visual direction fovea visual axis straight ahead Normal Retinal Correspondence ¾ retinal areas in the two eyes share a common subjective visual direction FL Retinal correspondence Normal Retinal Correspondence Empirical Horopter FR Normal Retinal Correspondence Empirical Horopter NRC ¾ corresponding retinal points are located on the same meridian and at the same distance from the fovea in each eye TL cyclopean eye TR FL NL NR FR TL FL NL NR FR TR 3

Empirical horopter Empirical horopter ¾ clinically defined area (3D space) where all points are seen singly ¾ fusion Vieth-Muller circle ¾ all exists points are seen singly ¾ requires ¾ model based upon assumption that eye is a perfect sphere ¾ NO Panum’s area ¾ NRC by definition stereopsis Stereopsis area around horopter where non-corresponding retinal points are stimulated without diplopia ¾ relative based upon ability to fuse slightly disparate images stereopsis exists single binocular vision localization of visual objects in depth ¾ limited by distance ( 20 feet) ¾ remember: monocular clues - important in interpretation of depth Sensory adaptations to strabismus Stereopsis Titmus stereo test ¾ allows stereopsis by presenting disparate images ¾ ¾ fly 4000 sec of arc ¾ ¾ 9/9 circles 40 sec ¾ ¾ suppression ARC diplopia confusion Random-dot stereogram ¾ no monocular clues 4

Sensory adaptations to strabismus Diplopia Confusion confusion - rare - perception of 2 images superimposed Sensory adaptations to strabismus Suppression Suppression ¾ strabismus ¾ confusing images originating from the retina ¾ central inhibition to avoid diplopia ¾ typically seen in children ¾ clinically, can give clues about etiology and age of onset of strabismus ¾ dense amblyopia ¾ ARC fusion - simultaneous perception of similar images - stimulate retinal points which normally do not correspond Sensory testing Why bother? ARC ¾ can give insight into etiology of strabismus ¾ can help with surgical plan ¾ helps to prepare the patient post-op Tests for retinal correspondence ¾ Based upon principle that images that are less “alike” are harder to fuse ¾ Tests FL FR that make images less alike (red filter) are more dissociating and therefore reveal suppression easier i.e. diplopia NR 5

Tests for retinal correspondence Tests for Retinal Correspondence Bagolini bagolini lenses DISSOCIATION Synoptophore Red Filter Worth four-dot ¾ Striated lenses produce streaks before the R and L eye at 45 and 135 degrees Afterimage test Tests for Retinal Correspondence Synoptophore ¾ major amblyoscope synoptophore 6

Tests for Retinal Correspondence Worth four-dot ¾ Test ¾ Very for fusion dissociating WORTH FOUR DOT Patient’s view FUSION WORTH FOUR DOT Patient’s view WORTH FOUR DOT NRC - fusion eyes aligned SUPPRESSION OD ARC - fusion WORTH FOUR DOT Patient’s view SUPPRESSION OS eyes deviated 7

Tests for Retinal Correspondence Afterimage test ¾ must have central fixation each eye tested separately streak of light - horizontal image on fixing eye - vertical image on deviated eye ¾ result independent of eye position ¾ ¾ Afterimage test ¾ ¾ Right 6th nerve palsy WORTH FOUR DOT Patient’s view central cross represents direction of fovea results independent of alignment Medial rectus trauma ESOTROPIA UNCROSSED DIPLOPIA HOMONYMOUS 8

WORTH FOUR DOT Patient’s view Clinical example Bagolini lenses ARC - peripheral fusion 5 year old - BMR age 2 for esotropia EXOTROPIA ¾ “holds” in small angle CROSSED DIPLOPIA ¾ HETERONYMOUS ¾ ¾ WORTH FOUR DOT Patient’s view Bagolini lenses OS OD (10 PD) ET ACT - builds to ET 20 what may sensory testing reveal? would you operate? SENSORY TESTING Suppression OD OS ARC FUSION DOUBLE MADDOX ROD Test for torsion Peripheral Fusion Streaks are placed vertically and perceived horizontally Eccentric Fixation ¾Fixation 9

ANGLE KAPPA Angle between “line of sight” and the corneal/pupillary axis ¾ Positive ¾ Negative patient looks - patient looks XT ET Amblyopia Eccentric fixation - fixation is not at the fovea ¾ MOST COMMON CAUSE OF UNILATERAL POOR VISION IN CHILDREN ¾ Prevalence 2-4% ¾ PREVENTABLE!!!! Angle kappa - fixation is at the fovea - must use ophthalmoscope Amblyopia Amblyos - (Greek) “dullness of vision” opia - from ops (Greek) vision ¾ Has come to refer to decreased vision in the setting of a “normal exam” ¾ Accepted definition: 2 lines difference in acuity between the eyes 10

Hubel and Weisel 1970’s ¾ Nobel Prize winners ¾ identified “sensitive period” for development Amblyopia - pathogenesis ¾ Amblyopia M and P cell mal-development severe sensory deprivation causes reduced cell size of normal binocular vision ¾ Lateral Geniculate Body Clinical relevance - amblyopia Discovered that suturing lids of kittens resulted in atrophy of cell bodies in the LGN Amblyopia neurophysiology Lateral geniculate Amblyopia-Functional ¾ reversible ¾ ¾ ¾ anisometropic ¾ ¾ primarily defect of central vision abnormal early visual experience ¾ profound effect on neural function ¾ occipital cortex ¾ lateral geniculate ¾ receptive fields of neurons become large ¾ monocular and binocular cells affected Functional Amblyopia ¾ strabismic ¾ occlusion ¾ ¾ Child with high myopia right eye Normal left eye Secondary exotropia Must always correct refractive error and improve vision before considering strabismus surgery 11

Amblyopia - Organic Occlusion Amblyopia ¾ ¾ typically refers to ocular anomalies preventing optimal acuity ¾ abnormality may be subtle or undetectable ¾ “irreversible” ¾ may be diagnosed after failure to respond to occlusion therapy ¾ must remember that organic amblyopia may have superimposed functional amblyopia ¾ Organic cause Can result from patching Amblyopia - diagnosis Bilateral Amblyopia Pre-verbal ¾ fixation preference ¾ vertical prism test (8-10 PD) ¾ acuity OKN, FPL, Teller, VEP Verbal ¾ Allen pictures, numbers, letters ¾ 2 lines difference Amblyopia - Strabismus Fixation ¾ In classic “textbook” congenital esotropia infants alternate their fixation and do not become amblyopic 12

Amblyopia crowding phenomenon Amblyopia - Treatment ¾ correct refractive errors ocular problems - i.e. cataract, ptosis ¾ occlusion ¾ penalization (i.e. atropine) ¾ follow closely ¾ occlusion amblyopia - always check Va in “better” eye ¾ treat ACUITY ISOLATED LINEAR in amblyopes Essentials of treatment ¾ ¾ ¾ ¾ ¾ ¾ Amblyopia Treatment Study Group ¾ Looking at measurement of visual acuity z Efforts to standardize ¾ Effects of treatment on child and family ¾ Comparison of ¾ ¾ ¾ ¾ Amblyopia Study Group Patching Regimens Pediatric Eye Disease Investigator Group ¾ Patient and family understanding and involvement Motivation/rewards Realistic goals Make it fun and easy Know when to stop Essentials of treatment ¾ ¾ ¾ ¾ z Drops and patching ¾ z Shorter vs. longer occlusion ¾ Archives of Ophthalmology 2003;121:603-611 189 children 7 y w/ moderate amblyopia (20/4020/80) Randomized to 2h/d vs. 6h/d patching Both groups performed 1 h per day of near visual activities Compliance consistent with other studies (poor) 4 m follow up Similar improvement in 2 groups Must take treatment seriously Often make contract with older kids Capitalize on their interests Visual challenging is essential Anatomy of the EOM’s ¾ Ocular alignment is determined by the extraocular muscles and their surrounding tissues ¾ PRIMARY POSITION the eye and head are directed straight ahead medial walls are parallel o lateral walls are 45 from medial walls o in primary position: SO, IO - 51 o SR, IR - 23 o MR, LR - 90 13

EOM’S Origin Inferior Oblique ¾ ¾ oval fibrous ring at the orbital apex EOMs originate at annulus EXCEPT: inferior oblique superior oblique levator palpebrae superioris Insertions of the EOM’s Oblique muscles ¾ ¾ Superior Oblique ¾ ¾ orbital apex above annulus (functional origin at trochlea LPS ¾ ¾ orbital apex above annulus Cardinal positions and yolk muscles SO longest tendon, RSR LIO courses inferior to SR ¾ ¾ maxillary bone, adjacent to lacrimal fossa, posterior to orbital rim Rectus muscles insert into sclera anterior to the equator via tendons Their anatomic relationship at the insertions forms the Spiral of Tillaux Thinnest sclera (.3mm) just posterior to the insertion Cardinal positions and yolk muscles insert posterior to the equator ¾ Insertions of the EOM’s Spiral of Tillaux Origin of the EOM Annulus of Zinn IO shortest tendon, RLR LMR LSR RIO LLR RMR courses inferior to IR RIR LSO LIR RSO 14