We have recently demonstrated age-related changes in the (threshold) chromatic contrast sensitivity function. This study evaluates whether there are senescent changes in suprathreshold chromatic contrast sensitivity as assessed by the contrast matching function (CMF). We compared luminance and chromatic CMFs for younger (age 18-30) and older (age 65-80) color normal subjects using stimuli that were perceptually anchored to the same physical S-axis contrasts. Sine-wave gratings were used to produce stimulation along the three cardinal axes of the MBDKL color space (S, L-M and Luminance axes). The stimuli were presented on a calibrated CRT at two mean luminance levels (5 and 30 cd/m2). Two S-axis stimuli were chosen as standards (2 cpd. at contrast levels 0.3 and 0.5) and subjects perceptually matched these to L-M and Luminance gratings of the same spatial frequency to obtain a complete set of standard gratings. Subjects then adjusted the contrast of the test gratings (0.5, 1, 2, 4 cpd for all axes, plus 8 cpd for the Luminance axis) to match the standards within each axis. The match and test gratings continuously alternated (presentation time 0.75s, ISI 1s) until a match was made. Absolute thresholds were also obtained for the S-axis standards. Due to changes in the visual system with age, the standard stimuli were closer to threshold for older subjects, and therefore might be expected to produce less contrast constancy. In general, however, the CMFs are very similar for both groups, although there is a slight loss in sensitivity at higher spatial frequencies for older subjects. These results suggest that the visual system compensates for losses in chromatic contrast sensitivity so that the perception of gratings at suprathreshold levels is relatively stable with age.
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