Establishing a new evaluation method defining and measuring outcome of occlusion treatment for unilateral amblyopia

Hong Yan

Purpose: To evaluate a new method defining and measuring outcome of occlusion treatment for unilateral amblyopia.

Methods: The efficacy of different patching regimens (2h/d, 6h/d and full-time) in 87 children (3-10y) with unilateral amblyopia were determined by visual acuity compared with the changes of sound eyes. The comparision of the different measurement for visual outcome were performed including the difference in final visual acuity of amblyopic eyes, the proportion of the deficit corrected, statistical visual acuity value calculated by formula "Euclidean Distance".

Results: At the end of occlusion therapy, visual acuity improved from baseline by an average of 3.2±2.5 lines (0.33±0.26 log MAR), and follow-up period was 19.71±14.61 months (1.62±1.20 years). The success rate was 86% (50 patients) at the end of patch therapy. Outcome of amblyopia treatment is usually expressed as the number of acuity chart lines gained or achievement of an arbitrarily adopted level of visual acuity. As binocular vision is optimised with equal visual input from each eye, the achievment of visual acuity in the amblyopic eye and its fellow should be considered. Improvement can be graded as the proportion of change in visual acuity with respect to the absolute potential for improvement by using formula "Euclidean Distance". This method could avoid bias of amblyopic children themselves subjectively.

Conclusions: This is the first report to establish a new evaluation method by using "Euclidean-distance" formula to calculate the improvement of visual acuity throughout the occlusion treatment of amblyopia.