Change of Deviation Angle after Monocular Occlusion in Intermittent Exotropia

ABSTRACT

PURPOSE: To measure the amount of increased angle of strabismus at far and near distance after 1 hour of monocular occlusion in intermittent exotropia and to evaluate the surgical outcome. METHODS: Fifty-five patients operated on for intermittent exotropia from May 2002 to February 2003 and followed for at least 6 months postoperatively were prospectively studied. In all patients, the angle of deviation was measured at 6 m and 33 cm before and 1 hour after monocular occlusion. Patients with an increase of exodeviation less than 5PD after occlusion were defined as non-responders, and were operated for the pre-occlusion angle (Group 1). Patients with an increased angle more than 5PD after occlusion were defined as responders, and were operated according to the pre-occlusion (Group 2) or post-occlusion (Group 3) angle. RESULTS: Thirty (54.5%) of the 55 patients were responders of distant deviation with an increase of 6.20+/-2.96 PD after occlusion. Forty-three (78.2%) of the 55 patients were responders of near deviation with an increase of 13.4+/-7.12PD after occlusion. Group 3 who underwent surgery for the increased angle after occlusion had a higher frequency of satisfactory surgical outcome (71.4%) than group 1 (68.0%) and group 2 (62.5%). However, these differences were not statistically significant (P>0.05, Chi-square test). CONCLUSIONS: The angle of strabismus in patients with intermittent exotropia who undergo surgery should be measured at 1 hour after monocular occlusion to improve the surgical outcome.