Strabismus (Squint)

Definition

• Misalignment of the eyes, causing impaired binocular vision.

• Different forms based on direction of deviation:

  • Esotropia: Eye turns inward

  • Exotropia: Eye turns outward

  • Hypertropia: Eye turns upward

  • Hypotropia: Eye turns downward

• Complication: Amblyopia (“lazy eye”) – can lead to permanent vision loss if untreated before ~age 7

Examination

Inspection

• Obvious misalignment of one or both eyes (constant/intermittent).

Hirschberg Test

• Assess corneal light reflex; asymmetry suggests strabismus.

Cover Test

• The uncovered eye will move/refocus if it was misaligned when the other is covered.

Uncover Test

• If the “covered” (potentially misaligned) eye moves to fixate when uncovered, that eye had been deviated.

Red Reflex

• Asymmetry or abnormal reflex → suspect an underlying pathology (e.g., cataract, retinoblastoma).

Red Flags (Urgent Referral)

• Limited Extraocular Movements (possible cranial nerve palsy).

• Nystagmus (neurological or vestibular pathology).

• Dysmorphic Features (suspect syndromic conditions).

• Abnormal Red Reflex (rule out retinoblastoma, congenital cataract).

• Secondary Causes: Intracranial pathology, e.g., tumour, stroke, or retinoblastoma.

Subtypes and Referral Recommendations

Esotropia

• Intermittent/Variable lasting >3 months: Semi-urgent referral (ophthalmology).

• Constant at any age: Semi-urgent referral.

Exotropia

• Intermittent or Constant: Usually non-urgent unless red flags present.

• Acute-Onset Constant: Immediate referral (concern for acute CN palsy or neurological cause).

Management

1. Eye Patching

   • Occluding the stronger (non-amblyopic) eye to strengthen the weaker eye and prevent amblyopia.

2. Corrective Lenses

   • Glasses or contact lenses to correct refractive errors (hyperopia, myopia).

3. Eye Exercises

   • Orthoptic exercises may help improve ocular muscle coordination.

4. Surgery

   • Strabismus surgery to realign eyes in persistent or severe cases or when conservative measures fail.

Notes

• Routine screening in children is critical to detect early strabismus and avoid permanent amblyopia.

• Strabismus often coexists in conditions like Down syndrome or cerebral palsy – consider multidisciplinary care.

• Acute-Onset Strabismus in an older child or adult may prompt neurological imaging to exclude CNS pathology.