Diagnostic occlusion test in intermittent exotropia

Abstract

We sought to determine the ideal length of time to use the diagnostic occlusion test (DOT) in the evaluation of patients with intermittent exotropia. Eighty-two consecutive intermittent exotropia patients were prospectively evaluated. After the routine ophthalmic examination, the DOT was applied for 1, 3, and 24 hours. The mean distance and near deviations, obtained with the DOTs, were compared, and the DOT periods at which deviations were stabilized were determined. The Nonparametric Tukey HSD test was used for statistical analysis. Before occlusion, the mean distance exotropia was 28.4 +/- 14.5, and the mean near exotropia was 25.7 +/- 15.5. After 1 hour of DOT, the exotropia measured 30.0 +/- 14.8 (p = 0.023) and 31.2 +/- 14.0 (p = 0.000), respectively. A clinically and statistically significant difference was not found after 3-hour and 24-hour DOT at either distance or near. Although the distance deviation stabilized after the 1-hour DOT and the near deviation was stabilized after the 3-hour DOT in intermittent exotropia cases, the change of mean near deviation between 1 and 3 hours was clinically negligible. The 1 hour DOT was at least as effective as the 3- and 24-hour DOT in most cases. Therefore, we recommend that the 1 hour DOT is sufficient for clinical applications.