Saccadic suppression under conditions of whiteout

We have measured the impairment of vision that accompanies a saccadic eye movement under whiteout conditions. Translucent plastic diffusers were fitted around the eyes to provide a luminous field without perceivable contours. Visual sensitivity of three subjects was tested by means of 10 msec luminance decrements of variable amplitude. We found that sensitivity was lower, by 0.7 to 1.1 log units, when the eyes were making 16 degree saccades than when they were at rest. Comparable amounts of saccadic suppression occurred under more usual Ganzfeld conditions. We therefore conclude that such minimal contours as are present in the Ganzfeld--fixation guides, minor surface blemishes, and the blurred outlines of the subject's nose and brow--have little effect on suppression. These results are consistent with the hypothesis that a centrally originating inhibitory process accompanies the initiation of the saccade.