Abstract
Suppression is a binocular condition that elicits repression of the visual field evoked by dissimilar inputs received by each eye, such as in amblyopia or when large interocular blur differences exist in normal vision. Contrast-modulated (CM) stimuli may be processed in more binocular areas than luminance-modulated (LM) stimuli (Wong, Levi & McGraw, 2001), and so interocular suppression may be heightened for CM rather than LM stimuli. Extent and depth of suppression was measured using a 24 deg circular stimulus split into rings and sectors. Each ring’s area was doubled from the central ring. Observers dichoptically matched the perceived modulation of a moveable sector to that of the surrounding ring, in order to measure the depth of suppression, for different levels of interocular dioptric blur (0-4D). Stimuli were presented on two head-mounted displays. Stimulus noise amplitude was also varied and depth of suppression measured. Increasing interocular blur revealed no local suppression scotomata within the binocular visual field, although a general increase in depth of suppression occurred at significantly different rates of 19% per dioptre with CM, compared to 8% with LM (p<0.05), stimuli. Increasing noise amplitude lessened the measured depth of suppression for LM stimuli, but enhanced the depth of suppression for CM stimuli. The depth of suppression increases across the visual field as interocular blur increases, and sensitivity to interocular differences in blur (possibly due to binocular disruption) for CM stimuli is greater. By varying noise strength, the measured suppression depth can be modified. In combination, these findings could be valuable in bringing observers with dense suppression into a measureable range, where more subtle changes in suppression depth could then be monitored.
Meeting abstract presented at VSS 2013