Clinical trial of the use of rotating grating patterns in the treatment of amblyopia.

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Abstract
Vision in amblyopia can be significantly improved by brief weekly periods of occlusion of the good eye while the child performs concentrated visuomotor tasks against a background of rotating gratings. A controlled trial to investigate the role played by the gratings in this procedure was conducted. A group (n = 33) of amblyopic children viewed a series of rotating gratings during treatment; the other group (n = 27) performed exactly the same visuomotor tasks against a homogeneous grey background. Particular attention was placed on the choice of tests of visual acuity to highlight the crowding phenomenon that is a characteristic feature of the visual loss in amblyopia. The chart selected was the Bailey-Lovie chart in which the number of letters on each line was held constant and the letter sizes and spacing were graded in equal logarithmic steps. Some improvement in vision occurred in almost all patients. The effectiveness of minimal occlusion therapy is supported. The difference between the improvement in vision of the 2 groups, averaged across all tests, was not statistically different. Only 1 of 6 acuity scores had a statistically significant difference in favor of the grating treatment group. This was observed only on patients with better than 6/60 vision where the overall improvement was itself very small. There was no detectable difference between the 2 groups in the rate of improvement of vision or in the tendency of the vision to be maintained or improved after cessation of treatment. Since the patients treated with gratings improved little or no more than those in the control group, most of the visual recovery apparently was propmoted by some other aspect(s) of the procedure.