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What is Alternative Exotropia, and management

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"Exotropia"[MeSH Terms] AND treatment

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intermittent exotropia management AAO preferred practice pattern

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Alternating exotropia is a type of manifest divergent strabismus in which either eye may deviate outward, usually alternately. The patient fixes with one eye while the other turns out, then may switch fixation so the opposite eye turns out.
Because fixation alternates, vision is often reasonably equal in both eyes and amblyopia is less common than in constant unilateral exotropia. However, binocular single vision and stereopsis may be reduced, particularly if the deviation is constant or poorly controlled.
It may occur as:
  • Intermittent alternating exotropia: eyes are aligned at times but one eye drifts outward with tiredness, illness, inattention, or bright light. A child may close one eye in sunlight.
  • Constant alternating exotropia: one eye is always outward, but the fixing eye alternates.

Assessment by an ophthalmologist

Assessment should include:
  • Visual acuity in each eye and amblyopia check
  • Cycloplegic refraction
  • Cover tests and prism measurement at distance and near
  • Assessment of control, fusion, and stereopsis
  • Ocular motility examination
  • Fundus examination to exclude reduced vision or retinal disease causing sensory exotropia
New-onset deviation with diplopia, ptosis, abnormal eye movements, headache, or neurologic signs requires urgent assessment.

Management

  1. Correct refractive error
    • Give appropriate spectacles, especially for myopia or meaningful anisometropia.
    • Selected intermittent cases may benefit temporarily from over-minus lenses, but this requires monitoring because it can encourage myopic progression.
  2. Treat amblyopia if present
    • Although uncommon in true alternating exotropia, unequal vision should be treated with optical correction and, when indicated, supervised patching or atropine penalization.
  3. Observation
    • Appropriate for intermittent exotropia with good, stable control, good stereopsis, and little functional or cosmetic concern.
    • Regular follow-up monitors frequency of drifting, control, angle, and stereoacuity.
  4. Non-surgical measures in selected intermittent cases
    • Part-time/alternate patching may reduce suppression and improve short-term control.
    • Orthoptic convergence exercises can help particularly when the deviation is greater at near, such as convergence-insufficiency type exotropia.
  5. Strabismus surgery
    • Usually considered when exotropia is constant, frequently manifest, control is poor or worsening, the angle is large, stereoacuity/fusion declines, or appearance causes significant concern.
    • Common procedures are weakening the lateral rectus muscle, often bilateral lateral rectus recessions, or a unilateral lateral rectus recession combined with medial rectus resection. The choice depends on the angle and exotropia pattern.
    • Surgery improves alignment, but undercorrection, recurrence, or overcorrection to esotropia can occur, so follow-up is needed.
For intermittent exotropia, the key treatment decision is control and binocular function, rather than simply the presence of an outward drift. Kanski notes that stable, effectively controlled cases are often observed, while poor or progressively deteriorating control favors surgery. Kanski’s Clinical Ophthalmology: A Systematic Approach, 10th ed., pp. 744-45. The AAO guidance summary similarly supports observation in young children with good fusional control and treatment when deviations are present most or all of the time.
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