Spatial vision and aging. I: Contrast sensitivity.

Contrast sensitivity functions (CSFs) were measured for two groups of healthy observers, a younger group with mean age 18.5 years and an older group with mean age 73 years. Although the two groups had virtually identical sensitivities to high spatial frequencies (gratings with narrow bars), the younger observers were three times more sensitive at low and intermediate spatial frequencies (gratings with wider bars) than were the older observers. Groups did not differ in relative sensitivity to gratings flickered at two rates, .33 and 6 Hz. The reduced sensitivity of older observers to low spatial frequencies cannot be explained in terms of optical factors or as the result of ocular pathology; it probably reflects a loss in that visual sub-system responsible for detecting low spatial frequency, temporally transient targets.