Studies on Dark Adaptation V Effect of Various Sizes of Centrally Fixated Pre-Exposure Fields on Foveal and Peripheral Dark Adaptation*

Abstract

The effect of various sizes of centrally fixated pre-exposures on foveal and peripheral dark adaptation was investigated. For both foveal and peripheral determinations, absolute brightness sensitivity was measured monocularly with a 1-deg circular test patch. Peripheral locations tested were 2, 6, and 15 deg on the horizontal meridian of the temporal retina. Foveal dark-adaptation curves were obtained after pre-exposure to fields which subtended 1, 2.5, 5, 10, and 37.5 deg diam. Peripheral dark-adaptation curves were obtained for three sizes of pre-exposure field at each location. In the fovea, each size was presented at 1 ft-L for 10 sec, 100 ft-L for 10 sec, and 1000 ft-L for 100 sec. In the periphery, each size was presented at 0.1 ft-L for 10 sec and 10 ft-L for 10 sec. The foveal results, with one exception, indicated that size is not a differential factor. In the periphery, the effects of size were most pronounced between those sizes which did and those which did not stimulate the area tested.