STEREOPSIS, SPATIAL-FREQUENCY AND RETINAL ECCENTRICITY

Stereoscopic depth discrimination thresholds increase with retinal ecc entricity and distance from the horopter, However, in contrast to spat ial resolution, the effects of spatial frequency on stereothresholds i n the periphery are unknown, For spatial vision, it is generally assum ed that the retina is comprised of a series of overlapping spatial fil ter mechanisms and that there is a commensurate increase in spatial sc ale as a function of retinal eccentricity, If the same holds true for mechanisms sensitive to stereoscopic depth, then stereo-thresholds for low spatial frequency stereoscopic stimuli may remain relatively inva riant across the visual field, while thresholds for relatively high sp atial frequency stimuli would increase, To further understand the role of the disparity sensitive mechanisms involved in depth discriminatio n, increment depth discrimination thresholds for both crossed and uncr ossed disparities were measured as a function of eccentricity for reti nal locations up to 10.0 deg along the horizontal meridian, We found t hat stereoscopic depth discrimination thresholds, as a function of dis tance from the horopter, increased in an exponential manner irrespecti ve of spatial frequency, Stereo-thresholds also increased as a functio n of retinal eccentricity, however, the rate of increase depended on t he spatial frequency composition of the stimuli, Best stereo-threshold s for stimuli composed of low spatial frequencies remained relatively invariant for retinal eccentricities up to 10.0 deg, while thresholds for the high spatial frequency stimuli increased with eccentricity.