The Meaning of Monocular Occlusion on Preoperative Evaluation in Basic Intermittent Exotropia

ABSTRACT

PURPOSE: To assess the clinical potential of one-hour monocular occlusion on preoperative alignment evaluation in basic intermittent exotropia. METHODS: Twenty-nine patients with basic intermittent exotropia who were preoperatively examined for one-hour monocular occlusion were selected (monocular occlusion group). Their records were reviewed retrospectively. The measured angle after one hour of monocular occlusion was used to determine the surgical target angle. The control group consisted of 29 patients whose age, sex and control state were similar to the monocular occlusion group. Measurement of the angle of strabismus was not done in the control group. Surgery was performed for the measured angle at six meters. The results of surgery were used to compare the groups relative to the control state. RESULTS: Fifteen patients (51.7%) had an increase in the distance deviation after one hour of monocular occlusion. Of the patients with good control, 78.6% (11/14) had an increase in the angle of misalignment. Only 26.7% (4/15) of patients with poor control experienced a change in the angle deviation (p<0.05). In all, 79.3% of patients in the study group and 75.9% of those in the control group had a satisfactory surgical outcome. Among the patients with good control, 85.7% of patients who underwent surgery for increased angle had a satisfactory outcome, compared with 71.4% of patients who underwent surgery for initial angle (p=0.375). CONCLUSIONS: One-hour monocular occlusion might help to prevent undercorrection after surgical treatment by identifying the hidden deviation, especially in the patients whose control over the distance deviation was good.