Comparison Of Angle Of Deviation And Types Of Strabismus Before And After Diagnostic Occlusion Test In Intermittent Exotropia

[BACKGROUND AND OBJECTIVE] Intermittent exotropia is usually intermitent and children often have the ability to control the exodeviation. In most cases, the exodeviation begins as exophoria, turns to intermittent exotropia, and then subsequently to manifest exotropia.Clinical factors associated with the decompensation of intermittent exotropia are the decrease of tonic convergence with advancing age, Momentary disruption of fusion by alternately covering each eye in a rapid fashion, as during the prism and cover test, is obviously insufficient to disrupt this powerful compensatory mechanism However,it may progress in amount and frequency, Giirlii and Erada recommend thatl hour DOT is sufficient for clinical applications.The occlusion test for differentiation between true and simulated divergence excess patterns is important.The aim of the present study to compare the angle of deviation and different types of intermittent exotropia before and after1-hour diagnostic occlusion test(1-hour diagnostic occlusion test) inpatients with intermittent exotropia.[METHODS] Retrospective case series study.Two hundreds and seven cases of inpatients with intermittent exotropia whose exodeviation had been measured when fixating at indoor distance target of6m and near target of33cm after were recruited from January2008to October2011in 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 accomdative target of6m and near accomdative target of33cm before and after1-hour diagnostic occlusion test,. Difference in measurements of mean angle of deviation at distance and at near before and after1-hour diagnostic occlusion test, were 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 after1-hour diagnostic occlusion test,. A Chi-square test was applied to compare the distribution of intermittent exotropia types before and after1-hour diagnostic occlusion test.[RESULTS] The mean exodeviations before and after1-huor diagnostic occlusion test were28.00±9.38prism diopter and29.85±9.59prism diopter respectively, when fixating at the distance target of6m, and the difference was significant(t=6.24, p=0.000). The mean exodeviations before and after1-huor diagnostic occlusion test, were28.17±9.92prism diopter and34.38±10.57prism diopter respectively, when fixating at the near target of33cm, and the difference was significant(t=12.23, P=0.000).The Bland-Altmann figure demonstrates that the angles of deviation before and after1-hour diagnostic occlusion test, at fixating distance target of6m showed comparable results, and that the angles of deviation before and after1-hour diagnostic occlusion test, at fixating near target of33cm showed imcomparable results.The difference of types of intermittent exotropia before and after1-hour diagnostic occlusion test, was significant (χ2=20.11, p=0.000)[CONCLUSIONS](1)1-hour diagnostic occlusion test, 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.(2)1-hour diagnostic occlusion test, is important for distinguishing different types of intermittent exotropia.