Amblyopia : assessment and treatment of binocular visual function

Unilateral amblyopia is a common neurodevelopmental syndrome characterized by reduced acuity and contrast sensitivity in the amblyopic eye (AE) & by abnormal inter-ocular visual function, e.g. reduced stereoacuity; without a concomitant etiological dysfunction. Standard treatment consists of a period of optical correction followed, when necessary, by occlusion therapy. Although ~70% children gain vision, this monocular therapy is limited by poor compliance and uncertain impact on stereo-function. Recently, binocular treatments have attempted to “rebalance” vision, by adjusting the intensity of monocular visual inputs (enhancing usage to AE or reducing fellow-eye -FE- one), while stimulating binocular cortical interactions. We have developed a “Balanced Binocular Viewing” (BBV) treatment that has patients spend an hour per day at home watching modified movies while wearing 3D goggles (to control what each eye sees). Movies present a blurred image to the FE and a sharp image to the AE. Performance (compliance and binocular-imbalance) is monitored throughout treatment using the child’s performance on a game, played during movie playback. Two ‘ghost’-stimuli, each made of a mixture of luminance increment/decrement, were presented dichoptically (some visible only through goggles): we quantified the mixture required for the child to be equally likely to report either ghost as ‘whiter’. Treating children (N=22) for 8-24 weeks lead to significant improvement in the AE acuity (mean gain: 0.27 logMAR). This is comparable to results achieved with occlusion, but elicits much higher compliance (89% of prescribed daily dose). We also compared our measure of binocular-imbalance to others, also quantifying sensory eye-dominance, to assess any test’s suitability to complement clinical practice. Pilot data measured with adult and children, with and without amblyopia, suggest that a variant of the ’ghost’-game is a potentially useful and efficient stand-alone clinical test with the advantage of being suitable for unsupervised home-based monitoring of patient’s binocular status.