A randomized controlled trial of unilateral strabismic and mixed amblyopia using occlusion dose monitors to record compliance

PURPOSE. To investigate compliance with patching therapy and the dose-effect relationship in occlusion therapy in amblyopia by recording the effective patching time using occlusion dose monitors (ODMs). METHODS. Fifty-two children with strabismic or mixed amblyopia (Snellen equivalent, 6/12-6/48) were given optimal refractive correction and randomly allocated for 12 weeks into three treatment groups: group 1, no patching; group 2, prescribed patching for 3 hours; and group 3, prescribed patching for 6 hours. The effective time of occlusion was monitored with ODMs continuously. Visual acuity (VA) was measured every 3 weeks with LogMAR ( logarithm of the minimum angle of resolution) Crowded Tests. RESULTS. In the 3- and 6-hour groups, mean (SD) compliance was 57.5% (30.8%) and 41.2% (30.9%), respectively, and mean effective patching time per day was 1 hour 43 minutes ( 55 minutes) and 2 hours 33 minutes (1 hour 52 minutes), respectively. The mean ( SD) improvement in logMAR VA of amblyopic eyes was 0.24 (0.17), 0.29 (0.14), and 0.34 (0.19) in groups 1, 2, and 3, respectively. There was no significant difference in compliance with the prescribed patching between the 3- and 6-hour groups. VA outcomes in the 3- and 6-hour groups were not significantly better than 0-hour patching. However, the VA of patients with eyes effectively patched for more than 3 hours improved significantly. A dose-effect relationship was observed. Age at treatment did not influence the visual outcome. CONCLUSIONS. Poor compliance with prescribed occlusion explains discrepancies in previous studies. No differences in the effect between the different prescribed patching periods were found. The dose-effect relationship observed should encourage development of methods such as educational intervention to improve visual outcome by increasing effective patching time.