Paediatric Strabismus

Strabismus presenting in infancy and childhood differs from adult disease because the visual system is still developing: misalignment can cause amblyopia, loss of stereopsis and abnormal sensory adaptations, and can signal serious disease (retinoblastoma, intracranial tumour, congenital cataract).

• Prevalence of about 3 to 5 percent in children. Types by age:
  • Neonates (to 2 to 4 months): transient intermittent misalignment is normal; constant misalignment beyond 4 months is abnormal.
  • Infantile esotropia (before 6 months), accommodative esotropia (2 to 4 years), intermittent exotropia (peak 2 to 5 years), sensory strabismus (from unilateral visual loss), acquired palsy (rare, needs imaging), and syndromic or congenital strabismus (Duane, Moebius, craniosynostosis, Down syndrome, cerebral palsy).
• Pseudostrabismus: broad nasal bridge and epicanthal folds mimic esotropia but with a central corneal light reflex and a normal cover test.
• Risk factors: family history, prematurity, low birth weight, neurodevelopmental disease, maternal smoking, high hypermetropia, anisometropia, and visual loss.

• Parents note an eye turn, especially with tiredness or illness; abnormal head posture; squinting in sunlight; poor depth perception, clumsiness.
• Amblyopia develops in about 30 to 50 percent of those with constant strabismus.
• Sensory strabismus: eye turns in the poorly seeing eye, leukocoria possible.
• Red flags: acute onset in older child, constant deviation after 4 months, incomitant deviation, nystagmus, papilloedema, headache and vomiting, ptosis, pupil changes, leukocoria, neurological deficit, abnormal head posture without clear cause.

• Photographic or video assessment from parents; Hirschberg corneal reflex; Krimsky prism reflex test (prism over the fixing eye) for poorly cooperative infants; cover tests (cover uncover, alternate prism cover) with fixation targets.
• Visual acuity by age (preferential looking, picture optotypes), fixation preference (the strength of fixation: central, steady, maintained), cycloplegic refraction, and dilated fundus examination.
• Ocular motility: versions, ductions, doll's head manoeuvre for pseudo abduction deficit, assessment of nystagmus.
• Stereoacuity (Lang, TNO), Worth four dot test; testing at distance and near; AC/A ratio.
• Neuroimaging (MRI) for neurological signs or incomitant strabismus; genetic testing for congenital cranial dysinnervation syndromes.
• Examine the family and photographs of early childhood.

• Priority is the visual pathway: correct refractive error, treat amblyopia (patching, atropine 1 percent), treat cataract, ptosis or other obstacles first.
• Early surgery for infantile esotropia between 6 and 24 months (bilateral medial rectus recession 5 to 7 mm) improves the chance of gross binocularity; later or delayed surgery gives alignment but poorer stereopsis.
• Intermittent exotropia: observation, overminus lenses (-1.00 to -3.00 dioptres), part time occlusion, and surgery when control deteriorates; surgery delayed until after age 4 to 5 if possible, while avoiding long suppression.
• Accommodative esotropia: full hypermetropic correction; bifocals for high AC/A; surgery only for non-accommodative residual deviation.
• Botulinum toxin (2.5 to 5 units per muscle under sedation) for infantile esotropia and acute acquired esotropia.
• Anaesthesia: general anaesthesia with oculocardiac reflex management (stop traction, atropine 0.02 mg/kg or glycopyrronium 0.01 mg/kg), postoperative nausea prophylaxis (ondansetron 0.1 mg/kg), risk of malignant hyperthermia in myopathy and strabismus (rare).
• Postoperative care: topical antibiotic steroid drops four times daily for 1 week, avoid swimming for 2 weeks, review at day 1 and at 1 week and 4 to 6 weeks, treat amblyopia, residual and recurrent deviation (about 20 to 50 percent need further surgery).
• Long term follow up: monitor refraction, amblyopia and alignment until age 8 to 10 years; psychosocial counselling (strabismus affects self-esteem and peer relationships).