Fifteen-minute monocular occlusion test compared with 45-minute monocular occlusion test in the evaluation of divergence excess intermittent exotropia.

Abstract

Background: The prolonged monocular occlusion (PMO) test is used to eliminate tenacious proximal fusion in patients with divergence excess intermittent exotropia. The minimum necessary duration of PMO is unknown. This study was designed to determine whether 15 minutes of PMO test is comparable to 45 minutes of PMO.

Methods: This prospective, randomized, observational study included 22 patients (5-14 years of age) diagnosed with divergence excess intermittent exotropia. The main outcome measure was the subclassification of divergence excess intermittent exotropia. The secondary outcomes were the effect of 15 minutes and 45 minutes of PMO on the size of the deviation, the near-distance disparity, and the accommodative convergence-accommodation (AC/A) ratio estimates.

Results: The number of patients classified as simulated, high AC/A ratio, and true divergence excess intermittent exotropia were identical following 15 minutes and 45 minutes of PMO. There were no statistically or clinically significant differences in the size of the near and distance deviations, the near-distance disparity, or the AC/A ratio following 15 and 45 minutes of PMO.

Conclusions: In our patient cohort, a period of 15 minutes of PMO was sufficient to unmask the true underlying deviation at near and properly subclassify divergence excess intermittent exotropia patients.