PERIODIC FLUCTUATIONS IN THE DARK ADAPTED THRESHOLD

Abstract

The course of parafoveal dark adaptation was measured by the method of flash perception. Periodic fluctuations in the threshold, instead of a smooth drop, are characteristic of the curves of some individuals. These fluctuations are observed in each eye independently. When alternate monocular measurements are made, the eyes are found to be in phase at times and out of phase at others. Binocular summation is suggested to explain the existence of damped fluctuations in the binocular threshold.