Esotropia

Inward deviation of one or both eyes. It is the commonest strabismus in early childhood.

• Types:
  • Infantile esotropia (onset before 6 months, large angle 30 to 60 prism dioptres, cross fixation, latent nystagmus, dissociated vertical deviation, inferior oblique overaction). Normal refraction.
  • Accommodative esotropia: refractive (hypermetropia of +2.00 to +6.00 dioptres, onset 2 to 3 years), non-refractive (high accommodative convergence to accommodation ratio, with larger angle at near), partially accommodative.
  • Acquired non-accommodative: basic, convergence excess, divergence insufficiency, acute acquired comitant (including sixth nerve palsy, intracranial tumour), sensory esotropia from visual loss, consecutive after exotropia surgery, and nystagmus blockage syndrome.
  • Incomitant: sixth nerve palsy, Duane retraction syndrome, thyroid eye disease with tight medial rectus, medial wall fracture entrapment, and myasthenia.
• Risk: hypermetropia, prematurity, family history, neurodevelopmental disorder.

• Infantile: constant large angle deviation, alternating or crossed fixation, pseudo abduction deficit (resolves with doll's head test), amblyopia in about 30 to 40 percent.
• Accommodative: intermittent then constant convergent squint, onset 2 to 3 years, with fixation on near objects, head tilt, closure of one eye, and normal abduction.
• Convergence excess: normal distance alignment, esotropia at near.
• Sensory esotropia: unilateral poor acuity and eye turn.
• Acute acquired esotropia in older children and adults: diplopia and headache; needs neuroimaging.
• Complications: amblyopia, loss of stereopsis, anomalous retinal correspondence, abnormal head posture, psychosocial effects.

• Cycloplegic refraction in all patients with esotropia; fundus examination to exclude retinoblastoma, optic nerve hypoplasia, cataract.
• Alternate cover and prism cover test at 6 m and 33 cm, with and without correction, and after wearing full hypermetropic correction; AC/A ratio (gradient or heterophoria method).
• Assess abduction fully (doll's head, patching one eye to uncover abduction), Duane signs (globe retraction on adduction, narrowing of palpebral fissure), nystagmus, DVD, inferior oblique overaction, A or V pattern.
• MRI brain for infantile esotropia with neurological signs, acute onset, papilloedema, or incomitance; thyroid function and orbital imaging in adults.

• Hypermetropic accommodative esotropia: full cycloplegic correction (glasses worn constantly), review every 3 to 6 months; reduce plus slowly after alignment is stable and fusion present.
• Convergence excess: bifocals (+2.50 to +3.00 add) or miotics (phospholine iodide 0.125 percent daily, with caution), or surgery (bimedial recession).
• Amblyopia treatment before surgery.
• Infantile esotropia: surgery between 6 and 24 months after amblyopia treated; bilateral medial rectus recession 5 to 7 mm for angles up to 60 prism dioptres (three or four horizontal muscle surgery for larger angles); unilateral recess resect for amblyopic eye; botulinum toxin 2.5 units to each medial rectus for early intervention; treat DVD and inferior oblique overaction at 3 to 5 years (superior rectus recession, inferior oblique recession).
• Acquired adult esotropia: prisms for small deviations; surgery after 6 months for stable cases; thyroid and sixth nerve causes managed by cause.
• Consecutive esotropia: observation, prism, further surgery.
• Follow up: amblyopia recurrence and cover tests at 3 to 6 monthly intervals until age 8 to 10 years.