Mechanism of Light Flicker Fusion during the Course of Dark and Light Adaptation

Abstract

IT follows from the data of Schaternikoff, Fedorov and Fedorova¹, R. Lithgoe and K. Tansley², and others, that during dark adaptation the critical flicker frequency for photopic vision is decreased. It has been shown by Alexanian and Livshiz in Orbeli's laboratory (Leningrad) that the same is the case in scotopic vision provided the effect produced by the change of threshold sensitivity during dark adaptation is eliminated. Critical frequency was therefore always determined for a light intensity which was a multiple of the threshold at the given moment. In the course of light adaptation the critical frequency is, on the contrary, increasing (R. Lithgoe and K. Tansley). The purpose of the present study was to analyse the causes underlying the above change of critical flicker frequency in the course of dark and light adaptation. Both dark and light adaptation were therefore studied by means of a special optical device which afforded the possibility of watching in a homogeneously illuminated field (angular size about 10°) the flickering of a central point visible within an angle of 1°, the brightness of which was equal to that of the background.