A binocular perimetry study of the causes and implications of sensory eye dominance.

Sensory eye dominance (SED) reflects an imbalance of interocular inhibition in the binocular network. Extending an earlier work (Ooi & He, 2001) that measured global SED within the central 6°, the current study measured SED locally at 17 locations within the central 8° of the binocular visual field. The eccentricities (radius) chosen for this, "binocular perimetry", study were 0° (fovea), 2° and 4°. At each eccentricity, eight concentric locations (polar angle: 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°) were tested. The outcome, an SED map, sets up comparison between local SED and other visual functions [monocular contrast threshold, binocular disparity threshold, reaction time to detect depth, the dynamics of binocular rivalry and motor eye dominance]. Our analysis shows that an observer's SED varies gradually across the binocular visual field both in its sign and magnitude. The strong eye channel revealed in the SED measurement does not always have a lower monocular contrast threshold, and does not need to be the motor dominant eye. There exists significant correlation between SED and binocular disparity threshold, and between SED and the response time to detect depth of a random-dot stereogram. A significant correlation is also found between SED and the eye that predominates when viewing an extended duration binocular rivalry stimulus. While it is difficult to attribute casual factors based on correlation analyses, these observations agree with the notion that an imbalance of interocular inhibition, which is largely revealed as SED, is a significant factor impeding binocular visual perception.