Ka Yee Kam¹, Dorita H. F. Chang¹; ¹Department of Psychology, The University of Hong Kong

Sensory eye dominance refers to the functional asymmetry between the two eyes, where the data from each eye is unequally weighted within the binocular neural network. In this study, we systematically measured sensory eye dominance at the fovea and at 16 isoeccentric locations in visually normal observers. Sensory eye dominance was measured using a dichoptic signal-in-noise motion (left-right) discrimination task. In this task, coherently moving signal dots and randomly moving noise dots were presented dichoptically to each eye. Observers were asked to make a two-alternative forced-choice judgement of the net motion direction of the dots. The magnitude of eye dominance was quantified as the ratio of the coherence thresholds (signal-to-noise ratio) obtained when signal dots were presented to one eye versus the other. Sensory eye dominance was measured at the fovea (0°), 3°, and 6° eccentricities. At each eccentricity, eight concentric locations were examined, corresponding to polar angles of 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°. Stimuli were scaled based on the cortical magnification factor. Results revealed that sensory eye dominance exhibited variation across the macular visual field. Specifically, individuals with relatively balanced eyes displayed variations in both the sign and magnitude of sensory eye dominance across the visual field. On the other hand, individuals with strong eye dominance tended to exhibit a consistent dominant eye, but with varying magnitudes of dominance observed across the visual field. Despite these variations, a significant correlation exists between sensory eye dominance in most tested locations, within observers. Our findings suggest that the degree of imbalance between the two eyes is not uniformly distributed across the visual field.