Reviewed by Steven Weifenbach
2017 OD Candidate-New England College of Optometry
Patching of the better-seeing eye is a common treatment for amblyopia to improve the visual acuity in the amblyopic eye. Recent studies have looked at active dichoptic tasks with perceptual training and iPad game play to improve visual acuity in the amblyopic eye by manipulating contrast to reduce interocular suppression. However, similar to patching, these tasks have encountered limited compliance due to low interest in some cases; reported noncompliance reaches up to 40% in some studies. Though these methods have found success in improving visual acuity in the amblyopic eye, noncompliance encourages research in alternative methods to provide treatment. The method studied in the article under review used popular movies presented in a dichoptic fashion to treat amblyopic patients.
Eligibility criteria included BCVA of ≥ 0.5 logMAR in the amblyopic eye, ≤0.2 logMAR in the fellow eye with an interocular difference of ≥0.2 logMAR. Children with strabismus were included only if visual axes had been successfully realigned by glasses and/or surgery. Success was defined as ≤5 prism diopters of residual strabismus. Eight amblyopic children between the ages of 4 and 10 years old who were eligible for the study. All subjects had been wearing their prescribed spectacle correction for at least 3 months and were not treated by for their amblyopia for the duration of the study.
Over 2 weeks, each child watched 6 dichoptically-manipulated movies while wearing glasses with polarized lenses. A high contrast image was shown to the amblyopic eye, while a low contrast image was shown to the fellow eye. Dichoptic motion coherence threshold was obtained in order to set the initial contrast level for the fellow eye. The fellow eye contrast was increased by 10% at each visit after the initial visit. Compliance was monitored by study personnel every 15-30 minutes and also by the child’s accompanying parent or guardian.
After the treatment, BCVA improved from 0.72 ± 0.08 logMAR to 0.52 ± 0.09, or about 2 lines (P = 0.003), in the amblyopic eye. The fellow eye did not show any significant change (P=0.19). Interocular suppression also showed no significant change (P=0.47). No significant harm or benefit occurred in the fellow eye, and stereopsis and depth of suppression remained the same.
Given the small sample number and lack of a control group, a larger study would be necessary to draw stronger conclusions about the benefit of dichoptic viewing of movies. It is noteworthy that studies using dichoptic iPad games have shown mixed results on improving suppression and stereopsis. The authors note that improved suppression results may be a consequence of improved perceptual learning that happens alongside the visual acuity gains, and the improved stereopsis reported may be due to using stereopsis tests which include monocular cues.
Regardless, it is interesting that the children showed about an average of 2 lines of improvement over 2 weeks compared to the 1 line of improvement by 120 hours of patching. This shows potential to be an effective therapy that may lend itself to higher compliance if the dichoptic glasses do not impede in the enjoyment of watching their favorite movies. The limit and permanency of improvement have yet to be investigated.