NEURAL LOSS CONTRIBUTES LITTLE TO ELEVATED DARK ADAPTATION THRESHOLDS IN THE ELDERLY

Title NEURAL LOSS CONTRIBUTES LITTLE TO ELEVATED DARK ADAPTATION THRESHOLDS IN THE ELDERLY
Author, Co-Author Linda Trick, Janet Nelson, Denise Jacquin, Carl Bassi
Topic
Year
1992
Day
Monday
Program Number
Poster 26
Room
Great Hall
Affiliation
Abstract With increasing age there is a systematic elevation in dark adaptation thresholds. Both neural and optical mechanisms have been implicated in this age-related visual loss. This study was designed to investigate the relative contributions of each of these factors to the dark adaptation deficits of the elderly. Dark adaptation was performed on each eye of 18 patients (age 60-79) who were monocular pseudophakes (contralateral eye phakic) as well as on 9 controls (age 22-30) using the Goldmann/Weekers dark adaptometer. Significant threshold elevations were evident in the older adults relative to the young control group (p=.0001) as well as in the phakic eyes relative to the pseudophakic eyes (p=.0027). Dark adaptation thresholds were lowest for the young patients (2.06 log units), significantly higher for the pseudophakic eyes (2.35 log units) and again significantly higher in the phakic eyes (2.52 log units)(p=.0048). While the difference in threshold between the pseudophakic and phakic eyes is likely to be the result of an optically induced deficit, the difference between young controls and elderly pseudophakes may reflect both neural and optical factors (including decrements due to senile miosis). When the results were corrected for age- related differences in pupil size, we found that at least 95% of the dark adaptation threshold elevation observed in elderly patients is accounted for by optical factors. Thus we conclude that neural loss appears to contribute little to the dark adaptation deficits of the elderly.
Affiliation of Co-Authors
Outline