Amblyopia is a neurodevelopmental disorder characterized not only by reduced visual acuity in the amblyopic eye but also by abnormal interaction between the two eyes, including interocular suppression and impaired binocular integration. Although treatment has traditionally focused on childhood, evidence of residual visual plasticity in adults has supported the development of binocular and dichoptic approaches aimed at restoring a more balanced contribution from both eyes.
Dichoptic therapy simultaneously stimulates both eyes while presenting different visual inputs to each eye. A common strategy is to reduce the strength of the image presented to the stronger eye, allowing the amblyopic eye to contribute more effectively during binocular viewing. This approach differs from conventional occlusion because visual information from both eyes remains available throughout treatment.
The intervention evaluated in this study is designed to adapt this therapeutic principle to the daily life of adults with amblyopia. In contrast to fully immersive virtual reality approaches that require participants to interrupt their usual activities and engage in dedicated virtual tasks or games, the intervention uses a Meta Quest 3 mixed-reality headset operating in passthrough mode. Participants can therefore continue to view and interact with their real-world environment while controlled visual processing is applied separately to each eye. The intervention is intended to integrate binocular visual rehabilitation into functional activities performed in the home environment.
During active treatment, the real-world scene presented to the amblyopic eye is preserved as close as possible to natural viewing conditions. The dominant eye receives the same spatially corresponding scene, but with a controlled reduction in contrast. This contrast manipulation reduces the functional advantage of the dominant eye without completely removing its visual information, creating a relative visual advantage for the amblyopic eye and encouraging its more active participation during binocular viewing. The intervention therefore aims to progressively rebalance the contribution of the two eyes rather than replace binocular vision with monocular viewing.
The degree of contrast modulation will be individualized according to the participant's visual function and adjusted throughout treatment according to visual performance. As visual function improves, the contrast difference between the eyes can be progressively reduced, bringing the visual inputs closer to natural binocular viewing conditions. This adaptive approach is intended to maintain an appropriate therapeutic challenge while avoiding unnecessary or excessive penalization of the dominant eye.
The study uses a randomized, placebo-controlled design in which both groups use the same mixed-reality device and follow the same training routine. The placebo condition preserves the device experience, duration, tasks, instructions, and home-use context but does not include the selective interocular contrast manipulation that produces active binocular rebalancing. This design allows the specific effect of the dichoptic treatment mechanism to be distinguished from nonspecific effects related to repeated visual activity, familiarity with the device, attention, and treatment expectations.
The home-based intervention is also designed to support objective monitoring of treatment exposure. Information such as session completion, effective training duration, interruptions, visual settings, task performance, adherence, and tolerability may be recorded to characterize the actual treatment dose and support individualized progression. Functional activities will be selected according to the participant's visual ability and safety, allowing the difficulty of the training to increase gradually as adaptation and visual performance improve.
In addition to determining the clinical effect of the binocular intervention, the study uses a multimodal assessment approach to characterize visual, retinal, and cortical changes associated with treatment and to investigate whether any improvements persist after treatment has ended. This approach is intended to provide a broader understanding of the functional and neurobiological response to home-based augmented reality binocular rehabilitation in adults with anisometropic amblyopia.
