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P.M. Pearson, L. Schmidt, N. Ly, W.H. Swanson; Chromatic and Achromatic Contrast Sensitivity: Reliability, Variability and Detection of Visual Loss . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2120.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To assess the reliability and variability of a custom perimetric instrument that measures chromatic and achromatic contrast sensitivity. Methods: Using a custom perimetric test that employs an equal energy white background to reduce the effects of lenticular density on tritan sensitivity, sensitivity to large (3º) and small (0.6º) chromatic and achromatic stimuli was measured in 32 young (M=23.4 ± 3.2 years) and 27 older (M=67.2 ± 8.3 years) observers. Measurements were obtained at 12º eccentricity. Between–subject variability was assessed as the standard deviation for each of the groups. Within–subject variability included measures of test–retest variability and short–term fluctuation. Test–retest variability was assessed by comparing thresholds obtained one week apart. The slope of the psychometric function fit with maximum likelihood estimation to the data was taken as a measure of short–term fluctuation. Results: Thresholds for the small chromatic stimuli were outside of the range attainable on the monitor for 4 people. Higher sensitivity for large chromatic stimuli increased the dynamic range of the test enabling us to obtain reliable (low false positives and negatives) measurements from all participants. In contrast, at least one location had to excluded due to low reliability for 3 of the younger and 8 of the older observers when the stimuli were small and chromatic. The effect of age on sensitivity to the large violet and large red targets was not significantly smaller than that obtained with the small white stimulus (t(18)=1.09, p=.29; t(18)=1.65, p=.12). Increasing the size of the achromatic (t(44)=3.29, p=.002), but not the chromatic (red, t(43)=0.87, p=.39; violet t(40)=0.89, p=.38), stimulus decreased the depth of defect. Between– and within–subject variability were both relatively small (< 2dB) and evidenced little influence of age. As a consequence of the small variability associated with the large chromatic tests, the chromatic tests identified significant aging losses in 21% (red) to 32% (violet) more of the participants than did the small achromatic test. Conclusions: Unlike achromatic sensitivity and SWAP, peripheral chromatic sensitivity for large stimuli does not show increases in variability with age while maintaining sensitivity to visual losses.
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