Comparative Study Of Measurements In Intermittent Exotropia

[Background] The long term postoperative results for patients with intermittent exotropia are sometimes not satisfactory due to high undercorrection ratio. The cause of this high rate of undercorrection may not uncover the full angle of the deviation when the patient with intermittent exotropia fixates on an accommodative target at 6 m. The measurements beyond 6 m, outdoor measurement, 1 hour occlusion and prism adaptation test had been suggested to uncover the full angle of the deviation for patients with intermittent exotropia. Despite measurements at indoor 30 m, outdoor measurement, 1 hour occlusion, prism adaptation in literature, we were unable to find any reports directly comparing these measurements together. Therefore, we performed this prospective clinical study to compare measurements at indoor 6 m, at indoor 30 m, outdoor,1 hour occlusion and prism adaptation for patients with intermittent exotropia and determine their role for uncovering the latent exodeviation.[Object] To compare measurements at indoor 6m, indoor 30m, outdoor, 1 hour occlusion and 3 hours prism adaptation for patients with intermittent exotropia and determine their role for uncovering the latent exodeviation.[Methods] A prospective, clinical trial was conducted of 60 consecutive patients with intermittent exotropia. After routine ophthalmic examination, exodeviation of all cases was measured at 33 cm and at indoor 6 m. On the basis of a 10PD value in the difference between 33 cm and indoor 6 m measurement, all of the patients were divided into the categories of basic type, divergence excess type and convergence insufficient type. Then sensory tests were performed with distance and near Worth Four Dot test and the Randot(?)Stereotest. Then indoor 30 m meaurment and outdoor meaurment were performed in-order. Finally 1 hour occlusion and 3 hours prism adaptation were performrd in randomize order at 15-minute to 30-minute intervals. An increase of 5 PD or more were defined as "increased exodeviation".[Results] The mean distance exodeviation after indoor 6 m measurement indoor 30 m measurement, outdoor meaurment,1 hour occlusion, prism adaptation were 30.53±10.83PD,32.6±10.83PD,34.2±10.38PD,35.93±10.53PD,36.15±11.40PD, respectively. As compared with indoor 6 m measurement, the exodeviation after indoor 30m measurement, outdoor measurement,1 hour occlusion, prism adaptation were significantly increased (P=0.001, P=0.000, P=0.000, P=0.000, respectively). The differences between indoor 30m measurement with outdoor measurement, occlusion, prism adaptation were significantly(P=0.020, P=0.000, P=0.000,respectively). As compared outdoor measurement,1 hour occlusion, prism adaptation with each other there were no significant difference (P>0.05). As compared 6m measurement, the percentage of patients showing increased exodeviation with outdoor measurement,1 hour occlusion, and prism adaptation (48.3%,60%,61.7%) were larger than that with 30 m measurement (30%,P<0.05). Whereas there were no significant differences during outdoor measurement,1 hour occlusion,3 hours prism adaptation as compared with each other (P>0.05). There was no difference between the 3 subtypes of intermittent exotropia in percentages with any one of the measurements (P>0.05). The difference between patients with and without increased exodeviation in relation to visual function were not significantly (P>0.05).[Conclusions] Indoor 30m measurement,outdoor measurement, 1 hour occlusion and prism adaptation can uncover the latent exodeviation of intermittent exotropia. outdoor measurement, 1 hour occlusion and prism adaptation can uncove larger exodeviation of intermittent exotropia than Indoor 30m measurement. Increased exodeviation had no correlation with the subgroups and the visual function of intermittent exotropia.