Accommodative Esotropia

Definition

• Age of onset: 6 months to 7 years (average ~2.5 years)
• Accounts for the majority of acquired childhood esotropias

AC/A Ratio

• Normal AC/A → Refractive accommodative esotropia
• High AC/A → Non-refractive (convergence excess) accommodative esotropia

Classification

1. Refractive Accommodative Esotropia

• Hypermetropia typically +2.00 to +7.00 D (Kanski) / +3.00 to +10.00 D, average +4.75 D (Wills Eye Manual)
• Deviation is equal at distance and near (difference <10 Δ)
• Onset: 18 months to 3 years
• Amblyopia is common at presentation
• AC/A ratio is normal

• Fully accommodative esotropia — deviation completely eliminated by full optical correction of hypermetropia; binocular single vision (BSV) restored at all distances
• Partially accommodative esotropia — deviation reduced but not eliminated by full hyperopic correction; residual angle is the non-accommodative component. Associated with bilateral congenital superior oblique weakness. Suppression common; ARC may occur (but of lower grade than in microtropia)

2. Non-Refractive Accommodative Esotropia (High AC/A Ratio)

a) Convergence Excess

• High AC/A ratio due to increased accommodative convergence (accommodation is normal, convergence is excessive)
• Normal near point of accommodation
• Straight eyes with BSV for distance
• Esotropia for near, usually with suppression
• Straight eyes through bifocals

b) Hypoaccommodative Convergence Excess

• High AC/A ratio due to decreased accommodation (weak accommodation requires increased accommodative effort → over-convergence)
• Remote near point of accommodation
• Straight eyes with BSV for distance
• Esotropia for near, usually with suppression

Clinical Features (Summary)

Investigations

1. Cycloplegic refraction (retinoscopy) — mandatory in all children with esotropia, irrespective of age
2. Cover test — assess deviation at distance and near, with and without glasses
3. Prism and cover test — quantify angle of deviation
4. AC/A ratio measurement — gradient method or heterophoria method
5. Sensory tests — assess suppression, ARC, BSV (Bagolini glasses, Worth 4-dot test)
6. Assessment for amblyopia — visual acuity in each eye

Treatment

Step 1 — Optical Correction of Refractive Error

• Under 6 years: Full cycloplegic hypermetropic refraction is prescribed (deduction only for the working distance of the retinoscope)
• Over 8 years: Refraction without cycloplegia; prescribe the maximum "plus" tolerated (manifest hypermetropia)

Step 2 — Bifocals

• Prescribed for convergence excess esotropia (high AC/A) to relieve accommodation for near, reducing accommodative convergence
• Executive bifocals are preferred so the child is forced to look through the lower segment at near
• Miotics (e.g., echothiophate iodide) — act as peripheral cholinergic agents, stimulate ciliary muscle directly, reducing the accommodative effort needed → decrease accommodative convergence; used as an adjunct or when glasses are poorly tolerated

Step 3 — Amblyopia Treatment

• Occlusion (patching) of the dominant eye when amblyopia is present
• Must be addressed before surgical correction

Step 4 — Surgery

• Partially accommodative esotropia — glasses reduce but don't eliminate the deviation; surgery addresses the residual non-accommodative component
• Convergence excess not controlled by bifocals
• Bilateral medial rectus recession is the standard procedure
• Surgery is performed after the angle is stable and optical treatment has been maximised

Step 5 — Ongoing Review

• Regular refraction is essential; hypermetropia may increase or decrease with age
• An accommodative element should be suspected if eyes appear straight post-surgery then become convergent again

Prognosis

• Fully accommodative refractive esotropia: Excellent prognosis for BSV if treated early; hypermetropia often decreases in adolescence, and glasses may eventually be discontinued
• Partially accommodative: Requires surgery; prognosis for BSV is guarded
• Convergence excess: Good if controlled by bifocals or miotics; surgery when needed

Key Clinical Images

Fig. 18.55 — Fully accommodative esotropia. (A) Right esotropia without glasses; (B) straight eyes with glasses. — Kanski's Clinical Ophthalmology, p. 755

Fig. 18.57 — Partially accommodative esotropia. — Kanski's Clinical Ophthalmology

Fig. 18.58 — Convergence excess esotropia. (A) Straight for distance; (B) right esotropia for near; (C) straight through bifocals. — Kanski's Clinical Ophthalmology, p. 756

Duane's Retraction Syndrome (DRS)

Definition & Pathogenesis

• Failure of innervation of the lateral rectus by a hypoplastic (absent or rudimentary) sixth nerve (abducens) nucleus
• Anomalous innervation of the lateral rectus by fibres from the third nerve (oculomotor)

• More common in females
• More commonly affects the left eye
• Often bilateral
• ~10% of cases are familial; associated mutations in several genes have been identified (e.g., CHN1, SALL4, HOXA1)
• Up to 50% of patients have associated systemic defects (see below)

Associated Systemic Features

• Deafness / hearing loss
• External ear abnormalities
• Speech disorder
• Skeletal abnormalities (e.g., Klippel–Feil anomaly — cervical vertebral fusion)
• Cervico-oculo-acoustic syndrome (Wildervanck syndrome)
• Radial ray defects
• Cardiac defects

Clinical Features

1. Limitation of abduction — complete or partial restriction (the most consistent finding)
2. Limitation of adduction — usually partial (due to anomalous co-contraction and tight LR)
3. Globe retraction on adduction — due to co-contraction of MR and LR
4. Narrowing of the palpebral fissure on adduction — secondary to globe retraction
5. Widening of the palpebral fissure on attempted abduction (in some cases)
6. Up-shoot or down-shoot in adduction — may be produced by the tight lateral rectus slipping over or under the globe, creating anomalous vertical movement ("bridle effect")
7. Deficiency of convergence — the affected eye remains fixed in the primary position while the unaffected eye converges
8. Compensatory head posture (face turn) — toward the side of the affected eye (in Type I); this positions the eye in adduction where the field of BSV is greatest, allowing binocular single vision and preventing amblyopia

Key point: Amblyopia, when present, is usually due to anisometropia rather than strabismus, because the face turn preserves BSV.

Classification — Huber's Types

Clinical Images

Investigations

1. Orthoptic assessment — cover test, prism and cover test, motility in all positions of gaze
2. Cycloplegic refraction — to detect anisometropia (cause of amblyopia)
3. Visual acuity — each eye separately (to detect amblyopia)
4. Forced duction test — to confirm mechanical restriction (LR is tight/fibrotic)
5. AC/A ratio — to assess accommodative component
6. Electromyography (EMG) — shows paradoxical firing of LR on adduction (confirmatory but rarely needed clinically)
7. MRI of brain/orbits — may show hypoplastic/absent abducens nerve and nucleus; also to exclude other cranial nerve pathology
8. Systemic assessment — hearing, skeletal survey if associated features are present

Treatment

Conservative (Majority of Patients)

• Optical correction of any refractive error (especially anisometropia)
• Amblyopia treatment (occlusion/patching) if present — usually due to anisometropia
• Observation with monitoring of CHP and binocularity

Surgical Indications

1. Loss of binocularity — failure to maintain or continue to use CHP
2. Cosmetically or psychosocially unacceptable head posture (in older children/adults)
3. Neck discomfort from chronic head turn
4. Cosmetically unacceptable up-shoots, down-shoots, or severe globe retraction
5. Significant deviation in primary position

Surgical Procedures

• Medial rectus recession (unilateral or bilateral) — to reduce esotropia and head turn in Type I; most commonly performed procedure
• Lateral rectus recession — reduces globe retraction and up-/down-shoots (by weakening the co-contracting LR)
• Muscle transposition — superior and inferior rectus (or superior rectus alone) transposed to the lateral rectus insertion to improve abduction when it is severely limited
• Faden procedure — posterior fixation suture to reduce co-contraction effects

IMPORTANT: The lateral rectus of the involved side must NOT be resected, as this increases globe retraction.

Differential Diagnosis

Summary Box

Amblyopia

Definition

• Most common cause of monocular visual impairment in children (affects ~2–4% of the population)
• Develops during the critical/sensitive period of visual development (birth to ~7–8 years)
• Central vision is primarily affected; peripheral visual field usually remains normal

Pathogenesis

1. Abnormal binocular interaction (strabismus) → active cortical suppression of the deviating eye's image
2. Form vision deprivation (opacity, ptosis) → failure of pattern stimulation of the visual cortex
3. Image blur in one or both eyes (anisometropia, ametropia) → chronic defocus weakens cortical connections

Classification

1. Strabismic Amblyopia

• Most common type (along with anisometropic)
• Results from abnormal binocular interaction where there is continued monocular suppression of the consistently deviating, non-fixating eye
• Vision is worse in the consistently deviating eye
• Strabismus can lead to, or be the result of, amblyopia

2. Anisometropic Amblyopia

• Caused by a difference in refractive error between the two eyes
• The more ametropic eye receives a chronically blurred image — a mild form of visual deprivation
• May result from a difference as little as 1 dioptre; clinically significant at ≥1.50 D
• The involved eye nearly always has the higher refractive error
• Frequently associated with microstrabismus and may co-exist with strabismic amblyopia
• Can be seen with eyelid haemangioma or congenital ptosis inducing astigmatism

3. Stimulus Deprivation Amblyopia (Form Vision Deprivation)

• Results from physical obstruction of the visual axis preventing pattern stimulation
• Caused by:
  • Unilateral congenital cataract
  • Corneal opacity/scar
  • Persistent foetal vasculature (PFV)
  • Ptosis covering the pupil
• Can be unilateral or bilateral
• Most severe and most difficult to treat — produces profound amblyopia rapidly in infancy
• Bilateral deprivation (e.g., bilateral congenital cataracts not treated early) causes bilateral amblyopia

4. Bilateral Ametropic Amblyopia

• Results from high symmetrical refractive errors, usually high bilateral hypermetropia
• Both eyes affected equally due to chronic bilateral defocus
• Less severe than deprivation amblyopia; can improve with spectacle correction alone

5. Meridional Amblyopia

• Caused by uncorrected astigmatism (usually >1 D) persisting beyond the period of emmetropization in early childhood
• Image blur in one meridian only
• Can be unilateral or bilateral

6. Occlusion Amblyopia (Iatrogenic)

• Amblyopia induced in the fellow (previously normal) eye as a result of excessive patching or overuse of atropine
• Prevented by appropriate monitoring intervals (1 week per year of age)

Diagnosis

Clinical Criteria

• In the absence of organic lesion: a difference in BCVA of two Snellen lines or more (or >1 log unit) between the two eyes is indicative of amblyopia

Symptoms

• Usually none — often discovered incidentally on routine vision screening
• History of squint, patching, or muscle surgery as a child may be elicited

Signs

1. Reduced BCVA in the amblyopic eye not fully correctable with refraction and not explained by organic lesion
2. Crowding phenomenon — individual letters read more easily than a full line (letters in a row); more marked in amblyopes; must be accounted for when testing preverbal children
3. Neutral-density filter effect — in reduced illumination, VA of an amblyopic eye is reduced much less than an organically diseased eye (helps distinguish amblyopia from organic disease)
4. Trace relative afferent pupillary defect (RAPD) — may be present in severe amblyopia (care needed to direct light along same axis in strabismic patients to avoid false positives)
5. Eccentric fixation — the amblyopic eye may fixate with a point other than the fovea (seen in dense strabismic amblyopia)

Investigations / Workup

1. Visual acuity assessment — age-appropriate methods:
   • Infants: fixation and following behaviour; comparison of objection to occlusion of each eye
   • Preverbal children: preferential looking tests (Teller acuity cards), Cardiff acuity cards
   • Older preverbal: Kay picture tests, Sheridan-Gardiner single optotype test
   • School age: Snellen chart, logMAR chart
2. Cover-uncover test — evaluate eye alignment; detect strabismus
3. Cycloplegic refraction of both eyes — mandatory; detects anisometropia and refractive errors
4. Fundus examination — to exclude organic disease before commencing amblyopia treatment (organic disease and amblyopia may co-exist)
5. Fixation behaviour — central/steady/maintained (CSM) in the amblyopic eye; eccentric fixation testing with visuoscope
6. Electrophysiology (VEP) — if acuity does not respond to treatment or organic disease suspected
7. Imaging (MRI) — if neurological cause suspected

Sensitive/Critical Period

Treatment

Step 1 — Treat the Underlying Cause

• Remove any media opacity (e.g., surgery for cataract) immediately
• Correct ptosis if covering the pupil

Step 2 — Optical Correction (Refractive Adaptation)

• Prescribe full cycloplegic hypermetropic correction
• For children under 6 years: full cycloplegic refraction
• For convergence excess / anisometropia: symmetrically reduce hyperopia by ≥1.50 D if needed
• Allow 6–12 weeks of refractive adaptation before adding occlusion — some improvement in VA may occur with spectacles alone (especially in anisometropic amblyopia)

Step 3 — Occlusion (Patching) of the Fellow Eye

• Adhesive patches placed directly over the eye are most effective (patches worn over glasses are not ideal — risk of peeking)
• Regimen: 2 to 6 hours per day (part-time); full-time in severe cases
• The younger the patient, the more rapid the likely improvement — but the greater the risk of inducing amblyopia in the normal eye
• Monitor VA in both eyes regularly during treatment
• Follow-up: 1 week per year of age (e.g., a 3-year-old reviewed after 3 weeks)
• The better the VA at the start of occlusion, the shorter the duration required
• If no improvement after 6 months of effective occlusion, further treatment is unlikely to be fruitful
• Poor compliance is the single greatest barrier to improvement

Step 4 — Penalization (Atropine)

• Atropine 1% drops once daily in the normal eye (with glasses)
• Shown to be equally effective as patching in mild-to-moderate amblyopia (VA 6/24 or 20/100 or better)
• Works best in anisometropic hypermetropic amblyopia
• Advantages:
  • Difficult for child to thwart
  • Less psychosocial stigma than patch (important in school-going children)
  • Weekend instillation may be adequate
• Effect can be increased by removing the hyperopic lens from glasses of the non-amblyopic eye
• Patch occlusion produces a quicker response than atropine

Step 5 — Optical Degradation

• High plus lens (e.g., +9.00 D or aphakic contact lens) to blur the image of the fellow eye
• Useful when other methods fail or are not tolerated

Step 6 — Strabismus Surgery

• In strabismic amblyopia, delay surgery until vision in both eyes is equal, or maximal vision has been obtained in the amblyopic eye

Step 7 — Protective Measures (If Treatment Fails)

• If treatment fails or patient presents outside the treatment age range, prescribe protective glasses to prevent accidental injury to the non-amblyopic eye
• Any child who does not achieve VA of at least 20/40: eye protection during sports (one-eyed athlete rule)

Prognosis

Key Points to Remember

• Organic disease must be excluded before commencing amblyopia treatment
• Organic disease and amblyopia can co-exist — a trial of patching may still be indicated
• The crowding phenomenon reflects impaired spatial interaction in the amblyopic visual cortex
• The neutral-density filter test helps distinguish amblyopia from organic pathology
• Never resect the lateral rectus in Duane syndrome (contextual reminder from previous topic)
• Amblyopia in Duane syndrome is usually due to anisometropia, not strabismus

• Detailed classification (including isoametropic, anisometropic, strabismic, and organic types)
• Critical period neurophysiology (Hubel & Wiesel experiments, ocular dominance columns)
• Fixation behaviour classification (central, eccentric — parafoveal, paramacular, peripheral)
• Eccentric fixation — distinguished from eccentric viewing; measured with visuoscope/ophthalmoscope
• Neutral density filter test — differentiating amblyopia from organic disease
• Pleoptic treatment (Cüppers' method) — historical treatment for eccentric fixation
• Sensory adaptations in amblyopia — suppression scotoma, ARC, microtropia

Amblyopia — Comprehensive Answer (von Noorden Framework)

Definition

• Affects ~2–4% of the general population
• Most common cause of monocular visual impairment in children and working-age adults
• Preventable and treatable if identified during the critical period

Pathogenesis — The Critical Period & Cortical Basis

Critical / Sensitive Period

• Critical period: Birth to approximately 7–8 years for strabismic amblyopia; may extend into the teens for anisometropic amblyopia (where some binocularity is preserved)
• Deprivation amblyopia is most severe when it occurs in the earliest months of life

Hubel & Wiesel — Ocular Dominance Columns (von Noorden references extensively)

• Monocular deprivation during the critical period causes a dramatic shift in ocular dominance — cortical neurons that were formerly driven by both eyes become driven exclusively by the non-deprived eye
• Binocular cells in V1 are almost completely lost after strabismus (Neuroscience: Exploring the Brain)
• These changes do not occur outside the critical period — underlying the age-dependency of amblyopia

Mechanism

1. Abnormal binocular interaction (strabismus) → active cortical suppression of the deviating eye's image to avoid diplopia → if constant and monocular, leads to strabismic amblyopia
2. Form vision deprivation (cataract, ptosis, corneal opacity) → failure of pattern stimulation → cortical connections of the deprived eye weaken
3. Chronic defocus (anisometropia, ametropia) → blurred retinal image → impaired cortical development of the affected eye

von Noorden's Classification

1. Strabismic Amblyopia

• Most common type (along with anisometropic)
• Abnormal binocular interaction: constant monocular suppression of the consistently deviating, non-fixating eye
• The fovea of the squinting eye is suppressed to avoid confusion; if this suppression is constant and unilateral → strabismic amblyopia (Kanski)
• Vision worse in the consistently deviating, non-fixating eye
• Strabismus can lead to, or be the result of, amblyopia

2. Anisometropic Amblyopia

• A difference in refractive error between the two eyes
• The more ametropic eye receives a chronically blurred image — a mild form of visual deprivation
• Can result from a difference as little as 1 dioptre (clinically significant at ≥1.50 D)
• The involved eye nearly always has the higher refractive error
• Frequently associated with microtropia and may co-exist with strabismic amblyopia
• Mixed (strabismic + anisometropic) amblyopia is recognised by von Noorden as one of the most common combinations

3. Stimulus Deprivation Amblyopia (Amblyopia ex Anopsia)

• Physical obstruction of the visual axis → failure of pattern (form) stimulation of the cortex
• Causes: unilateral congenital cataract, dense corneal opacity, PFV (persistent foetal vasculature), ptosis covering the pupil
• Most severe type — produces profound amblyopia very rapidly in infancy; recovery most difficult
• Can be unilateral or bilateral (bilateral congenital cataracts not treated promptly → bilateral amblyopia)

4. Isoametropic (Bilateral Ametropic) Amblyopia

• Von Noorden's term for amblyopia from high symmetrical bilateral refractive errors, usually high hypermetropia
• Both eyes affected equally; no interocular suppression
• Less severe than deprivation amblyopia; can improve with spectacle correction alone

5. Meridional Amblyopia

• Caused by uncorrected astigmatism (usually >1 D) persisting beyond the period of emmetropisation
• Image blur in one meridian only; produces a "notch" in the visual acuity at the axis of the uncorrected cylinder
• Can be unilateral or bilateral

6. Organic Amblyopia (von Noorden)

• Von Noorden recognised a subcategory of amblyopia associated with minor structural anomalies not detectable clinically — e.g., subtle macular abnormalities, optic nerve hypoplasia
• Important to consider when amblyopia fails to respond to treatment

Sensory Adaptations to Strabismus (von Noorden)

1. Suppression

• Cortical inhibition of the image from the deviating eye to avoid diplopia and confusion
• Monocular suppression — image from the dominant eye always predominates → leads to amblyopia
• Alternating suppression — switches between eyes → amblyopia less likely
• Facultative suppression — occurs only when eyes are misaligned (e.g., intermittent exotropia)
• Obligatory suppression — present at all times, irrespective of alignment

2. Abnormal Retinal Correspondence (ARC)

• Non-corresponding retinal elements acquire a common subjective visual direction
• The fovea of the fixating eye is paired with a non-foveal element of the deviated eye
• A positive sensory adaptation (vs. suppression which is negative) — allows some anomalous binocular vision in the presence of a small-angle heterotropia (Kanski)
• Most common in microtropia/small-angle esotropia
• Detected by: Bagolini striated glasses, Worth 4-dot test, Maddox rod

3. Eccentric Fixation (von Noorden's landmark contribution)

• Definition: The amblyopic eye fixates with a retinal point other than the fovea — a parafoveal, paramacular, or peripheral point is used for fixation
• This is distinct from eccentric viewing (a compensatory strategy in macular disease)
• Occurs only in dense strabismic amblyopia
• The eccentric point may eventually develop its own "pseudo-fovea" — a false principal visual direction
• Classification by location:
  • Parafoveal — within 1° of the fovea (mildest)
  • Paramacular — 1–3° from fovea
  • Peripheral eccentric fixation — >3° from fovea (most severe)

• Visuoscope (ophthalmoscope with fixation target) — the examiner projects a target onto the fundus and notes which retinal point the patient uses to fixate; if the target falls outside the fovea, eccentric fixation is confirmed
• VCTS (visual cortex test): rarely used
• Haidinger brushes — patient perceives a rotating figure centred on the fovea; in eccentric fixation, the figure appears off-centre

Diagnosis

Clinical Criteria (Kanski / von Noorden)

• In the absence of organic lesion: a difference in BCVA of two Snellen lines (≥0.2 logMAR) between the two eyes is indicative of amblyopia

Symptoms

• Usually none — discovered on routine vision screening
• History of squint, patching, or muscle surgery as a child may be elicited

Signs

Workup

1. Visual acuity — age-appropriate methods:
   • Infants: fixation and following; objection to occlusion of each eye
   • Preverbal: Teller acuity (preferential looking), Cardiff cards, Sheridan-Gardiner
   • School-age: Snellen / logMAR chart (crowding bars used)
2. Cover / uncover and alternate cover test — detect and quantify strabismus
3. Cycloplegic refraction (retinoscopy) — mandatory; detects anisometropia
4. Fundus examination — exclude organic disease before starting treatment
5. Fixation assessment — central/steady/maintained (CSM); visuoscope for eccentric fixation
6. Sensory tests — Bagolini glasses, Worth 4-dot, Maddox rod (suppression, ARC)
7. Neutral-density filter test — differentiate amblyopia from organic pathology
8. Electrophysiology (VEP/ERG) — if no response to treatment or organic disease suspected
9. MRI — if neurological cause is suspected

Treatment

Principles (von Noorden)

1. Eliminate the cause of amblyopia
2. Provide the best possible optical correction
3. Force use of the amblyopic eye by penalising the dominant eye
4. Treat as early as possible — within the critical period

Step 1 — Treat the Cause

• Cataract surgery (deprivation amblyopia) — must be performed urgently, within weeks of diagnosis in infancy; followed by optical rehabilitation (contact lens/glasses) and immediate patching
• Ptosis correction if visually significant
• Corneal opacity — keratoplasty if necessary

Step 2 — Optical Correction (Refractive Adaptation)

• Full cycloplegic hypermetropic correction prescribed
• Under 6 years: full cycloplegic refraction without reduction
• Over 8 years: maximum tolerated "plus" (manifest hypermetropia)
• Allow 6–12 weeks of refractive adaptation before adding occlusion — some VA improvement may occur with spectacles alone (especially anisometropic amblyopia)

Step 3 — Occlusion (Patching)

• Adhesive patches applied directly over the eye are most effective (patches over glasses allow peeking)
• Regimen: 2–6 hours/day (part-time); full-time in severe cases
• Younger patients improve more rapidly, but have greater risk of occlusion amblyopia in the normal eye
• Monitor VA in both eyes regularly: 1 week per year of age per visit
• Better initial VA → shorter treatment duration required
• No improvement after 6 months of effective occlusion → further treatment unlikely to help
• Poor compliance is the single greatest barrier (Kanski)

Step 4 — Penalization (Atropine)

• Atropine 1% drops once daily in the dominant eye — blurs its near vision, forcing use of the amblyopic eye
• Equally effective as patching for mild-to-moderate amblyopia (VA 6/24 / 20/100 or better) (Wills Eye Manual)
• Best for anisometropic hypermetropic amblyopia
• Advantages: difficult for child to thwart; less psychosocial stigma; weekend-only instillation may suffice
• Patching produces a quicker response; atropine preferred when compliance with patching is poor

Step 5 — Optical Degradation

• High plus lens (e.g., +9.00 D) or removing the corrective lens from the dominant eye's glasses
• Useful when other methods fail or are not tolerated

Step 6 — Pleoptics (von Noorden — historical)

• Euthyscope method: The retina of the amblyopic eye is first dazzled (bleached) using a bright light, protecting the fovea with a small disc. The fovea recovers first, establishing it as the dominant fixating point.
• Haidinger brush training: The patient learns to direct their fixation to the true fovea using the entoptic Haidinger brush phenomenon (visible only to the fovea under polarised blue light)
• Largely replaced by conventional patching in modern practice

Step 7 — Dichoptic Therapy (Modern)

• Binocular treatment using separate stimuli to each eye (e.g., video games, virtual reality)
• Based on von Noorden's and later work on binocular interactions
• Aims to reduce suppression and improve binocular function alongside VA

Step 8 — Strabismus Surgery

• In strabismic amblyopia: delay surgery until VA in both eyes is equal or maximal improvement achieved in amblyopic eye
• Correcting the deviation eliminates the substrate for suppression and consolidates gains

Prognosis

• If treatment fails or patient is outside treatment age: protective eyewear for the non-amblyopic eye; one-eyed athlete rule (protective sports glasses mandatory)

Summary — von Noorden's Key Contributions