Detection Thresholds for Point Sources in the Near Periphery
MICHIGAN UNIV ANN ARBOR OFFICE OF RESEARCH ADMINISTRATION
Pagination or Media Count:
Two observers have obtained visual detection thresholds for the foveal center and for thirty-two locations in the peripheral retina within a radius of 12 degrees from the fovea. The locations have fallen along eight equally spaced meridians of the visual field, at distances of 1, 2, 4, 8 and 12 degrees from the fixational center. A total of 368,250 observations have been made, utilizing the temporal forced-choice variant of the method of constant stimuli. The target was a circle, whose diameter subtended 1 minute of arc the exposure duration was .01 second. There were significant differences in sensitivity among the different meridians, the pattern of sensitivity differences differing at different levels of background luminance. The primary data concern the effect of the extent to which a target falls eccentric to the fixational center upon the threshold contrast. The threshold contrast was considerably higher for off-axis locations than for the fixational center at high levels of background luminance. It is possible to plot the relation between threshold contrast and background luminance for the foveal location and for the various peripheral locations. The data for each peripheral location exhibited a discontinuity which was more marked the farther was the location from the fixational center.
- Anatomy and Physiology