Critical Flicker Fusion Perimetry and the Adaptation Level of the Eye

Abstract

MOST scientists concerned with the physiology of vision agree that the temporal resolution of the cone system is greater than that of the rod system. In only a few of the experimental studies, however, is the evidence convincing that exclusively rods or exclusively cones were indeed functioning over some appropriate range of stimulus environments. Colour visibility, small stimulus fields, and widely discrete levels of adaptation have been tried with only indifferent success. Moreover, the cone system is reported only to be generally faster, not always so. Many of the studies find that the rods sometimes resolve light pulses at higher frequencies than do the cones. Our predictive knowledge of this whole problem is poor. We can probably safely assert only that a small dim stimulus in the retinal periphery will be less adequately resolved than a similar stimulus in or near the fovea, while, on the contrary, a large bright stimulus will be better resolved in the periphery. There is some additional evidence for an annulus of high resolution at about 10° from the fovea.