Sequential stereopsis: a simple demonstration.
Most people strongly prefer to use back-and-forth eye movements in order to discriminate 3-dimensional distances among targets that are widely separated from each other in direction. This viewing strategy permits sequential stereopsis: a comparison between the foveally-seen pre-saccadic disparity of one target with post-saccadic disparity of the other. This note describes a simple and qualitatively compelling demonstration of the usefulness of sequential stereopsis, in a situations in which classical stereopsis, with steady fixation, is greatly degraded. Targets of high-spatial-frequency texture are used, with details that can be resolved foveally before and after saccades, but that are unresolvable in peripheral vision. Back-and-forth eye movements between such textured targets, separated by 8-10 deg from each other, led to estimates of threshold that average less than 45 sec arc disparity (corresponding to about 0.18% of viewing distance): some of the best performances ever reported for targets so widely separated.
Enright
J T
JT
Neurobiology Unit, Scripps Institution of Oceanography, La Jolla, CA 92093, USA.
D000293:Adolescent; D000328:Adult; D003867:Depth Perception / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology; D004215:Distance Perception / Q000502:physiology; D005133:Eye Movements; D005403:Fixation, Ocular; D006801:Humans; D008875:Middle Aged; D010364:Pattern Recognition, Visual / Q000502:physiology; D012684:Sensory Thresholds / Q000502:physiology; D015348:Vision, Binocular / Q000502:physiology