Comparison of angle of deviation and types of strabismus before and after diag-nostic occlusion test in intermittent exotropia

Abstract

Objective To compare the angle of deviation and types of intermittent exotropia before and after 1-hour diagnostic occlusion test (1h-DOT) in patients with intermittent exotropia.Methods Retrospective case series study.Two hundreds and seven cases of inpatients with intermittent exotropia whose exodeviations were measured before and after 1h-DOT were recruited from January 2008 to October 2011 in the Eye Center of Provincial Hospital affiliated to Shandong University.Prism and alternative cover test was used to evaluate the exodeviation fixating at indoor distance accommodative target of 6m and near accommodative target of 33cm before and after 1h-DOT.Difference in measurements of mean angle of deviation at distance and at near before and after 1h-DOT was assessed using paired t test.Bland-Altmann method was used to evaluate the agreement of mean angle of deviation at distance and at near before and after 1h-DOT.A Chi-square test was applied to compare the distribution of types of in-termittent exotropia before and after 1h-DOT.Results The mean exodeviations fixat-ing at the distance target of 6m before and after 1 h-DOT were 28.00±9.38 PD and 29.85±9.59 PD,respectively,and the difference was significant (t =6.24,P =0.000).The mean exodeviations fixating at the near target of 33cm before and after 1h-DOT were 28.17±9.92 PD and 34.38±10.57 PD respectively,and the difference was significant (t =12.23,P =0.000).The Bland-Altmann figure demonstrated that the angles of deviation fixating at distance target of 6m before and after 1h-DOT showed comparable results,and that the angles of deviation fixating at near target of 33cm before and after 1h-DOT showed incomparable results.The difference of types of intermittent exotropia before and after 1h-DOT was significant (x2=20.11,P =0.000).Conclusions 1h-DOT has a strongly effect on the angle of deviation at near and has a weak effect on that at distance in patients with intermittent exotropia.1h-DOT is important for distinguishing different types of intermittent exotropia. Key words: Exotropia ; Intermittent ; Measurements ; Exodeviation ;