👁️ Strabismus (Squint) = ocular misalignment. In children, if untreated, it leads to amblyopia (lazy eye) because the brain suppresses the deviating eye. 👉 Any persistent squint beyond 3 months of age needs ophthalmology referral.

📍 About

Strabismus = inability to align both eyes simultaneously under normal viewing conditions.
One or both eyes may deviate inwards (esotropia), outwards (exotropia), upwards or downwards.
Untreated → suppression of one eye by the brain → abnormal visual pathway development → amblyopia (functional blindness in the affected eye).

🧬 Aetiology

Visual system develops until ~8 years → requires congruent images from both eyes.
If images differ, the brain suppresses the deviating eye.
Suppression → underdeveloped optic pathways → irreversible amblyopia if untreated.

⚠️ Risk Factors

Family history of strabismus.
Refractive error: uncorrected hyperopia (farsightedness).
Medical conditions: Down syndrome, cerebral palsy, perinatal brain injury, stroke, or head trauma.

🔎 Causes

Strabismus can be congenital or acquired. Key types include:

Congenital (Infantile) Esotropia: Presents within 6 months; inward turning of one/both eyes; risk of amblyopia.
Accommodative Esotropia: Ages 2–4; hypermetropia → excessive focusing effort; improves with glasses.
Intermittent Exotropia: Eye drifts out, esp. when tired; may close one eye in sunlight.
Nerve Palsies (CN III, IV, VI): Sudden onset misalignment + diplopia; neurological cause until proven otherwise.
Restrictive: Thyroid eye disease, trauma, scarring.
Duane Retraction Syndrome: Congenital; absent CN VI; retraction of globe on attempted abduction.
Convergence Insufficiency: Difficulty with near tasks, headaches, double vision.
Trauma: Muscle entrapment or nerve injury → diplopia.
Neurological: MS, stroke, tumour → urgent neuroimaging.

🩺 Clinical Assessment

Cover–uncover test: Gold standard for detecting latent/manifest squint.
Document visual acuity in each eye separately.
Note if worse when tired, ill, or after prolonged near work.
Screening is essential in children (esp. school vision checks).

💊 Management

Correct refractive error: Glasses or contact lenses.
Prism lenses: Reduce eye strain and realign image.
Occlusion therapy: Cover the good eye → force use of the lazy eye → prevent amblyopia.
Vision therapy: Exercises to improve coordination and fusion.
Surgery: Eye muscle surgery (recession/resection) for persistent squint; often combined with vision therapy afterwards.

📚 References

American Academy of Ophthalmology – Strabismus Guidelines
NICE CKS – Childhood vision problems

📌 Exam Tip

👶 Any constant squint >3 months in a child = urgent referral.
🔑 Infantile esotropia: early, constant, inward squint.
🔑 Accommodative esotropia: age 2–4, improves with glasses.
🚨 Acute onset strabismus + diplopia in an adult = think CN palsy → neuroimaging.

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Strabismus (Lazy Eye)