Rapid Light Adaptation of Localised Areas of the Extra-foveal Retina

Abstract

The subjective disappearance of peripherally fixated objects has usually been regarded merely as an obstacle to satisfactory observation. The course of local adaptation of a stimulus subtending 40 × 80 minutes of arc on a dark ground has been investigated for the dark adapted extra-foveal retina under conditions of steady fixation, with variation of intensity, wavelength and eccentricity, and for several observers. A time delay of a few seconds followed by a rapid reduction of subjective brightness was always found, the subjective image vanishing outside the paracentral region. It appears that the process is characteristic of both rod and cone units. The origin of the effect is discussed. La disparition subjective des objets en vision peripherique continue n'a ete ordinairement consideree que comme un obstacle a une observation satisfaisante. L'adaptation locale du stimulus de 40 × 80 minutes d'arc en fond obscur, dans les conditions d'observation continue et de fixation soutenue, a ete etudiee pour la re...