Abnormal Binocular Rivalry Dynamics in Amblyopia: A Potential Diagnostic Marker.

PURPOSE: Amblyopia is a neurodevelopmental disorder characterized by monocular deficits and interocular suppression. Binocular rivalry, where perception alternates between dissimilar images, is a powerful tool to probe this suppression. However, the dynamics of sustained binocular rivalry remain poorly characterized in amblyopia. This study aimed to comprehensively characterize these dynamics in individuals with amblyopia compared to visually-normal controls. METHODS: Eleven adults with amblyopia and eight controls continuously reported their perception during a binocular rivalry task through keypresses. We used custom calibration to ensure stable fusion. Key metrics included complete reversal rates (transitions between differing monocular percepts), incomplete reversal rates (transitions to mixed percepts and back), and eye preference indexes. RESULTS: Although most participants with amblyopia experienced sustained rivalry, their dynamics were severely abnormal. Complete reversal rates were profoundly reduced, and more time was spent seeing the fellow eye percept. Distinct signatures emerged for amblyopia subtypes, shedding light on underlying mechanisms: anisometropic patients exhibited higher incomplete reversal rates than strabismic/mixed patients, suggesting higher binocular noise levels in anisometropic amblyopia. Combining these metrics enabled perfect separation between groups (control, anisometropic, or strabismic/mixed), even with just four minutes of data, in our adult sample. CONCLUSIONS: Binocular rivalry dynamics are fundamentally altered in amblyopia, revealing disrupted reversal mechanisms. These dynamics distinguish amblyopia from normal vision and differentiate between etiologies. The perfect separation achieved suggests that quantifying rivalry dynamics holds significant potential as a rapid noninvasive diagnostic tool.