A 5-year-old child has an exotropia with deviation of 30 prism diopters (PD) at near and 40 PD at distance. The increased deviation at distance is characteristic of which type of exotropia, and what does the distance-near disparity indicate?

• A Convergence excess esotropia; high AC/A ratio
• B Basic exotropia; no fusional mechanism difference at near or far
• C Convergence insufficiency; near deviation greater than distance
• D Divergence excess intermittent exotropia; the deviation is greater at distance because divergence fusional amplitude is inadequate for far gaze while near convergence compensates ✓

Explanation

Intermittent exotropia is the most common form of childhood exotropia. Divergence excess type shows deviation greater at distance (≥10 PD more at distance than near), as divergence fusional amplitude is inadequate at far fixation while near convergence (amplified by the AC/A mechanism and proximal convergence) partially controls the deviation at near. Basic exotropia has equal distance and near deviation; convergence insufficiency exotropia has a greater near deviation. Bilateral lateral rectus recession is the typical surgical treatment for divergence excess exotropia.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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