Senescent changes in scotopic contrast sensitivity

Scotopic contrast sensitivity functions (CSFs) were measured for 50 observe rs between the ages of 20 and 88 years. Using a maximum-likelihood, 2-alter native, temporal forced-choice threshold-estimation algorithm, scotopic CSF s were measured at 7 spatial frequencies ranging from 0.2 to 3.0 cpd, with mean retinal illuminance equated for observers at - 0.85 log scotopic Trola nds. For each stimulus condition, eight cycles of a horizontal sinusoidal g rating were presented within +/- 1 S.D, of a 2-D Gaussian-spatial envelope and within a 1-s Gaussian-temporal envelope. Stimuli were centered on the n asal retina along the horizontal meridian 6 degrees from the fovea. Scotopi c CSFs were found to be low-pass. Statistically significant age-related dec lines in contrast sensitivities were found for spatial frequencies at or be low 1.2 cpd. There was also a statistically significant decrease in the hig h frequency cut-off with age (P < 0.01). An explanation of these results in terms of optical factors is rejected, while the results are consistent wit h age-related changes in the magnocellular pathway. (C) 1999 Elsevier Scien ce Ltd. All rights reserved.