The Influence of Monocular Occlusion on the Preoperative Ocular Alignment and the Surgical Outcome in Basic Intermittent Exotropia

Purpose: This study was to evaluate the influence of monocular occlusion on the preoperative ocular alignment and the surgical outcome of basic intermittent exotropia. Methods: We examined 42 patients with basic intermittent exotropia who were operated and followed for at least 6 months postoperatively from January 2001 to August 2002. In all patients, angle of misalignment measured while the patients fixate on an accommodative target at 6m and 33cm, and after 2 hours of monocular occlusion. The subjects were divided into two groups: Gruop 1-far angle of misalignment did not increase after 2 hours of monocular occlusion, Group 2-far angle of misalignment increased in 3PD or more after 2 hours of monocular occlusion. Group 2 underwent surgery for the increased deviation of far angle. Results: Among 42 patients with basic intermittent exotropia, Group 1 included 27 (64.3%) patients and Group 2 15 (35.7%) patients. In Group 2, the mean (SD) increase in the angle of exotropia after 2 hours of monocular occlusion was 5.33 (2.74)PD. The success rate of surgery was 77.8% (21/27 patients) in Group 1, 93.3% (14/15 patients) in Group 2 at 6 months after surgery and 70.4% (19/27 patients), 93.3% (14/15 patients) at the final visit. There was no statistically significant difference (p> 0.05). Conclusions: This study showed the significant influence of monocular occlusion on the ocular misalignment before surgery and surgical outcome in basic intermittent exotropia.