Article reviewed by Sari Schwartz, OD 2017-New England College of Optometry
The purpose of this preliminary study is to investigate the effectiveness of using a modified iPad for the treatment of hyperopic anisometropic amblyopia. Amblyopia causes more vision loss in the population less than forty-five years of age than all other ocular problems combined, excluding refractive error. This common and detectable abnormality of spatial vision can be treated, potentially allowing for more equal quality images to be received by each eye and then further processed by the brain.
Seven male and female subjects, aged three to seven years old, were selected to participate in this study. Each participant had some degree of hyperopic anisometropic amblyopia and <10Δ exophoria at distance and near to ensure no strabismic component to their amblyopia. The subjects were first managed with full refractive correction and then underwent different treatment modalities for their amblyopia. The first treatment group consisted of three subjects using Occlu-pad training for one hour every day, while the two subjects in the second treatment group performed the same Occlu-pad training in addition to three hours of daily occlusion therapy. To serve as a control, the final group’s two subjects performed occlusion therapy only, with no use of the Occlu-pad.
The Occlu-pad training works by displaying different images to the subject’s eyes. This can be achieved by placing a circular polarizing filter over the amblyopic eye and a light reduction filter over the patient’s normal eye, and removing the polarizing film layer from the liquid crystal display of the iPad. Since the polarizing filter of the glasses matches the screen output and the light reduction filter does not, the amblyopic eye can view the task at hand while the non-amblyopic eye only views the white screen background. With Occlu-pad use, patients were instructed to train by either actively playing web games or passively watching videos for one hour a day for a total of four weeks. Occlusion-treated patients were instructed to patch their dominant eye for three hours a day. All groups were limited to no more than two months treatment.
Out of the five patients that underwent Occlu-pad training with or without occlusion, all had a notable improvement in visual acuity in their amblyopic eye. The two patients that underwent strictly occlusion therapy had little or no increase in visual acuity in their amblyopic eye. The greatest improvement was seen in the first month of training and the worse the starting acuity, the better the achieved ending acuity.
This study shows that there are several advantages to treating anisometropic amblyopia using a modified iPad. First, the Occlu-pad can accurately track compliance by automatically logging dates and hours of playtime on the device. This feature allows study results to be better compared between subjects. Existing treatment options are not always well-understood or successful due to poor compliance and an inability to reliably track time spent under occlusion. Another advantage of the Occlu-pad is that it allows amblyopia training to be done in the comfort of a patient’s home on a device that is familiar to the millennial generation. Training with a portable and user-friendly device allows treatment to be initiated and completed at the convenience of the patient. Lastly, the Occlu-pad is a binocular training device that allows amblyopic patients to use both eyes while being treated. This allows patients to train in a setting that better represents how they function in their daily lives.
Many factors must be considered when analyzing the results of this study. First, subjects in the study totaled only seven. In order to draw a stronger conclusion and extrapolate results to more hyperopic anisometropic amblyopes, it is important for future research to include a larger study cohort. Secondly, using different web games and videos leads to variability in treatment. Playing web games requires the patient to actively respond to the task, which potentially improves hand-eye coordination. However, merely watching a video is a passive form of training that theoretically serves less benefit. Although this variability may maintain the interest of the subjects throughout the treatment period, it creates a distinction between actively and passively treated patients. Additionally, future studies should aim to select subjects with more similar refractive errors, and treat all subjects for the same amount of time. In this study, the amount of anisometropia ranged from +2.5D to +6D, and the training time varied from 240 to 960 minutes. This inconsistency makes establishing guidelines for the amount of training time for different severities of anisometropic amblyopia very difficult. Finally, no definitive activities we were outlined for the patients undergoing three hours of occlusion treatment. By assigning subjects an activity while they are patching, stricter control and therefore more accurate strategies can be established for treating patients with hyperopic anisometropic amblyopia.
Significant improvement in visual acuity of the amblyopic eye with use of full optical correction, occlu-pad training, and/or occlusion treatment demonstrates that hyperopic anisometropic amblyopia is treatable. By devising a scheme for different signals to be received by each eye, modified iPad activities can improve our amblyopic patients’ vision and lives. Overall, this is an excellent preliminary study exploring the efficacy of such iPad training activities for amblyopia, but using more subjects and tighter control of the activities performed during treatment will increase the validity of future studies.