Comparison of the characteristics of patients with intermittent exotropia according to response to diagnostic monocular occlusion.

PURPOSE

To compare the characteristics of intermittent exotropia patients according to their response to the diagnostic monocular occlusion test.

STUDY DESIGN

Retrospective study.

METHODS

A retrospective review was performed of 141 patients with intermittent exotropia who had taken a monocular occlusion test before surgery. We classified the patients into 3 groups based on the response to monocular occlusion. The increase group was defined as those patients having an increase in deviation of ≥ 5 prism diopters (PD) after monocular occlusion as compared with the maximum measured angle. The decrease group was defined as those patients having a decrease in deviation of ≥ 5 PD. Otherwise, patients were classified as having no change. The patients' characteristics were compared among the groups.

RESULTS

At distance fixation, 9 patients (6.5%) were classified as increase, 92 patients (66.7%) as no change, and 37 patients (26.8%) as decrease after monocular occlusion. At near fixation, 50 patients (35.5%) were classified as increase, 65 patients (46.1%) as no change, and 26 patients (18.4%) as decrease. At distance fixation, no significant differences were found between the parameters of the patients in the increase group and those of the patients in the other 2 groups. In patients with a small maximum angle of exodeviation at near fixation and with few visits, the deviation at near fixation significantly increased after diagnostic occlusion.

CONCLUSION

Fifty-two patients (36.8%) showed an increase of ≥ 5 PD during distance or near fixation after monocular occlusion. In patients with a small maximum angle at near fixation and with few visits, it would be beneficial to perform the monocular occlusion test before surgery to reveal the maximal deviation angle, regardless of exotropia type.