LANDOLT-C RECOGNITION IN ELDERLY SUBJECTS IS AFFECTED BY SCOTOPIC INTENSITY OF SURROUND ILLUMINANTS

In a previous study of young adults age 20-40, we demonstrated that lo w-contrast Landolt-C recognition was better with smaller pupils than w ith larger pupils even though task retinal illuminance was higher for larger pupils. Pupil size in these studies was controlled by the spect rum of the far surround illumination, which was prevented from affecti ng task luminance. The present study used the same procedures as our p revious study with seven healthy elderly adult subjects between the ag es of 61 and 66. Because senile miosis is a characteristic of the agin g eye, spectral changes in the surround might be expected to produce r elatively smaller changes in pupil size and hence performance. Althoug h the.scotopically enhanced surround lighting produced relatively smal ler pupil size changes than in young adults, the performance enhanceme nts were surprisingly comparable to those of young adults. As in the p revious study, the task was recognition of the orientation of the gap in the C that was presented on a CRT with contrasts varying from 18-80 percent. Two surround illuminants were compared, both provided a lumi nance of 53 cd/m2 on the front wall at visual angles larger than 30 de grees. Subjects had at least 20/20 vision and performed the task with their spectacles if normally used.