Abstract
We investigated spatio-chromatic contrast sensitivity in both younger and older color-normal observers. We tested how the adapting light level affected the contrast sensitivity and whether there was a differential age-related change in sensitivity. Contrast sensitivity was measured along three directions in colour space (achromatic, red-green, yellowish-violet), at background luminance levels from 0.02 to 2000 cd/m2, and different stimuli sizes using 4AFC method on a high dynamic range display. 20 observers with a mean age of 33 y. o. a. and 20 older observers with mean age of 65 participated in the study. Within each session, observers were fully adapted to the fixed background luminance. Our main findings are: (1) Contrast sensitivity increases with background luminance up to around 200 cd/m2, then either declines in case of achromatic contrast sensitivity, or remains constant in case of chromatic contrast sensitivity; (2) The sensitivity of the younger age group is higher than that for the older age group by 0.3 log units on average. Only for the achromatic contrast sensitivity, the old age group shows a relatively larger decline in sensitivity for medium to high spatial frequencies at high photopic light levels; (3) Peak frequency, peak sensitivity and cut-off frequency of contrast sensitivity functions show decreasing trends with age and the rate of this decrease is dependent on mean luminance. The data is being modeled to predict contrast sensitivity as a function of age, luminance level, spatial frequency, and stimulus size.
Highlights
The human visual system undergoes both optical and neural changes as we age
Our study investigates the joint effects of age and luminance level on achromatic and chromatic contrast sensitivity functions
Achromatic contrast sensitivity decreases with age across all spatial frequencies
Summary
The human visual system undergoes both optical and neural changes as we age. In addition to optical factors, neural changes in human visual system with age lead to changes in contrast sensitivity as well [10] especially in scotopic and mesopic range [11]. Previous studies have investigated age-related changes in both achromatic [9, 12, 10] and chromatic contrast sensitivity at low luminance levels [13, 14, 15, 16, 17, 18, 19, 20] and proposed models to characterize age-dependent contrast sensitivity functions [21, 22]. We are investigating the joint effects of luminance (ranging from 0.02 to 2000 cd/m2) and age on spatio-chromatic sensitivity
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