Difficulties in the definition of ‘stereoscotoma’ using temporal detection of thresholds of dynamic random dot stereograms

Abstract

Temporal detection thresholds are reported from two subjects to dynamic random dot stereograms (DRDSs) of both crossed and uncrossed disparity. The stimuli were 1 degree square, of 0.25 degrees disparity and were presented at 81 positions in a 9 degree square central region. In both subjects crossed disparity stimuli were detected at shorter durations. One subject displayed particularly acute stereoscopic vision and presented a pattern of temporal thresholds increasing gradually with eccentricity. The other subject displayed evidence, particularly in response to uncrossed stimuli, of a ‘stereo-scotoma’ which was not evident in monocular testing or ophthalmologic examination. Criteria used to define ‘stereo-scotoma’ are discussed. It was concluded that, although left-right field differences may be found with a large subject sample, individual factors may be more important in the distribution of stereo sensitivity throughout the portion of visual field tested.