Abstract
Dichoptic movie viewing has been shown to significantly improve visual acuity in amblyopia in children. Moreover, short-term occlusion of the amblyopic eye can transiently increase its contribution to binocular fusion in adults. In this study, we first asked whether dichoptic movie viewing could improve the visual function of amblyopic subjects beyond the critical period. Secondly, we tested if this effect could be enhanced by short-term monocular occlusion of the amblyopic eye. 17 subjects presenting stable functional amblyopia participated in this study. 10 subjects followed 6 sessions of 1.5 hour of dichoptic movie viewing (nonpatched group), and 7 subjects, prior to each of these sessions, had to wear an occluding patch over the amblyopic eye for two hours (patched group). Best-corrected visual acuity, monocular contrast sensitivity, interocular balance, and stereoacuity were measured before and after the training. For the nonpatched group, mean amblyopic eye visual acuity significantly improved from 0.54 to 0.46 logMAR (p < 0.05). For the patched group, mean amblyopic eye visual acuity significantly improved from 0.62 to 0.43 logMAR (p < 0.05). Stereoacuity improved significantly when the data of both groups were combined. No significant improvement was observed for the other visual functions tested. Our training procedure combines modern video technologies and recent fundamental findings in human plasticity: (i) long-term plasticity induced by dichoptic movie viewing and (ii) short-term adaptation induced by temporary monocular occlusion. This passive dichoptic movie training approach is shown to significantly improve visual acuity of subjects beyond the critical period. The addition of a short-term monocular occlusion to the dichoptic training shows promising trends but was not significant for the sample size used here. The passive movie approach combined with interocular contrast balancing even over such a short period as 2 weeks has potential as a clinical therapy to treat amblyopia in older children and adults.
Highlights
Amblyopia is a neurodevelopmental disorder arising from abnormal visual experience during childhood over a period called “the period of susceptibility” or “the critical period” [1,2,3,4,5]
For the nonpatched group, the average value at baseline was 0 54 ± 0 37 logMAR and 0 46 ± 0 38 logMAR at the completion of training. This is a significant improvement of 0.08 logMAR, which is equivalent to almost one line on the visual acuity chart
The training did not affect the VA of the nonamblyopic eye with an average improvement of 0.04 and 0.05 logMAR in the patched and nonpatched groups, respectively, verifying that the improvement was not induced by any learning of the visual acuity measurement itself
Summary
Amblyopia is a neurodevelopmental disorder arising from abnormal visual experience during childhood over a period called “the period of susceptibility” or “the critical period” [1,2,3,4,5] It mainly manifests itself by a loss of binocular function, reduced visual acuity in one eye, the amblyopic eye, and it is the most frequent cause of unilateral visual loss in childhood. The presently accepted treatment for amblyopia consists of full optical correction [13] and monocular patching of the nonamblyopic eye to force the use of the amblyopic eye [14]. This treatment is only successful for young children, and it has been assumed that older children. No treatment is offered to these older patients as their amblyopia is thought to be fixed [1,2,3,4,5, 15, 16]
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