The effect of horizontal strabismus surgery on the vertical palpebral fissure width.

Objective: To compare vertical lid fissure width before and after medial or lateral rectus muscle recessions for horizontal strabismus.

Methods: In this prospective, noninterventional case series, vertical eyelid fissure width measurements were compared before and after treatment in consecutive patients undergoing extraocular muscle recessions for esotropia or exotropia. Digital imaging analysis was used to measure vertical lid fissure width. Each measurement was an average of three separate images.

Results: A total of 59 subjects were enrolled, including 42 for esotropia and 17 for exotropia. Mean postoperative vertical palpebral fissure width increased by 0.96 mm (11.9%; range, 0.64-2.5 mm) in esotropia patients and 1.00 mm (11.8%; range, 0.19-3.23 mm) in exotropia patients (P < 0.0001 in both groups.)

Conclusions: Recession of a rectus muscle for comitant horizontal strabismus may result in vertical widening of the palpebral fissure.