Epidemiology & Risk Factors

Prevalence: ~2–4% of pediatric population.
Normal variant: Intermittent strabismus is normal in infants < 4 months of age (due to immature ocular motor control). Persistence ≥ 4 months is pathologic.
Risk Factors:
- Prematurity / Low birth weight (LBW).
- Positive family Hx.
- Neurologic conditions: Cerebral palsy (CP), hydrocephalus, Down syndrome.
- Uncorrected refractive errors (e.g., hyperopia leading to accommodative esotropia).
- Ocular pathology: Retinoblastoma, congenital cataracts.

Clinical Features

Ocular Misalignment:
- Esotropia: Inward/nasal deviation (most common).
- Exotropia: Outward/temporal deviation.
- Hypertropia/Hypotropia: Vertical deviation (upward/downward).
Compensatory behaviors: Head tilt, abnormal head posture, or squinting/closing one eye in bright sunlight.
Visual symptoms:
- Young children: Suppression of image from the deviating eye (often asymptomatic, but leads to visual loss).
- Older children / Adults: Diplopia (double vision) or asthenopia (eye strain).

Initial / Bedside Screening:
- Corneal light reflex test (Hirschberg test): Asymmetric deflection of light off the corneas (normal = symmetric, central reflex).
- Cover test / Cover-uncover test:
  - Cover test: Detects manifest deviation (tropia). The uncovered deviating eye shifts to fixate when the straight eye is covered.
  - Cover-uncover test: Detects latent deviation (phoria).
Essential Workup:
- Cycloplegic refraction: To assess for uncorrected refractive errors (hyperopia).
- Dilated funduscopic exam: Crucial to rule out underlying intraocular pathology (e.g., retinoblastoma, optic nerve hypoplasia). c
Imaging (MRI/CT Orbit & Brain):
- Indicated if: Sudden/acute onset, paralytic/incomitant strabismus (CN III, IV, or VI palsy), presence of neurologic signs, papilledema, or suspected retinoblastoma/intracranial neoplasm.

Pseudostrabismus:
- Diff: False appearance of esotropia due to prominent epicanthal folds or a broad, flat nasal bridge. Shows symmetric corneal light reflex and normal cover test.
Retinoblastoma:
- Diff: Manifests with leukocoria (white pupillary reflex) and intraocular mass visible on fundoscopic exam / ocular US / MRI.
Cranial Nerve Palsy (CN III, IV, VI):
- Diff: Sudden onset, limited extraocular motility (incomitant deviation depending on direction of gaze). Often associated with trauma, ↑ ICP, ischemia, or neoplasm.
Congenital Cataract:
- Diff: Leukocoria, absent or abnormal red reflex; visual deprivation leads to secondary sensory strabismus.

Primary goal: Prevent irreversible amblyopia and preserve binocular vision (depth perception).

First-Line / Conservative:
- Refractive Correction: Prescribe corrective lenses (glasses) (curative for accommodative esotropia driven by hyperopia).
- Occlusion Therapy (for Amblyopia):
  - Patching the sound/dominant eye for several hours daily to force stimulation of the amblyopic eye.
  - Pharmacologic Penalization: Topical atropine drops placed in the sound eye (blurs near vision, forcing use of the amblyopic eye; alternative if poor patch adherence).
Second-Line / Surgical:
- Extraocular Muscle (EOM) Surgery (recession/resection):
  - Indicated for: Congenital (infantile) esotropia, persistent deviation despite full refractive/patching therapy, or large non-accommodative deviations.
  - Optimal timing: Usually performed early (prior to age 1–2) for congenital esotropia to maximize binocular fusion.
Refractory / Alternative:
- Botulinum toxin (Botox) injection: Direct injection into the overacting EOM (temporary realignment or adjunct in select cases).

Amblyopia (“Lazy Eye”): Cortical suppression of the deviating eye leading to permanent, irreversible loss of visual acuity if not corrected before visual cortex maturation (~age 7–8).
Loss of Stereopsis: Deficits in binocular depth perception.
Contracture of Extraocular Muscles: Chronic misalignment causing mechanical shortening of the affected rectus muscle.
Psychosocial and cosmetic impairment.

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