Age-Related Changes in Contrast Sensitivity in Central and Peripheral Retina

Abstract

Eight young (average age 20.4 years) and eight elderly (average age 64.4 years) observers took part in three experiments designed to study age-related changes in peripheral retinal function. A further eight young (average age 22.3 years) and eight elderly (average age 63.8 years) observers took part in a replication of experiment 3. All observers had normal or better-than-normal visual acuity and no evidence of ocular pathology. All testing was monocular and the eye with better visual acuity was used. In the first experiment contrast sensitivity was measured in central retina and 10 deg temporally, at spatial frequencies of 0.2, 0.8, 2.0, and 5.0 cycles deg−1. Young observers had better contrast sensitivities than older observers, but only at higher spatial frequencies (2.0 and 5.0 cycles deg−1). For both groups, contrast sensitivity was poorer with peripheral presentation of stimuli than with central presentation, but not for the lowest spatial frequency used (0.2 cycle deg−1). In the second experiment observers had to detect the presence of a sharp edge (square-wave luminance profile), while in the third and fourth experiments the target was a ‘fuzzy’ edge (sine-wave profile). Edges were again presented centrally or 10 deg temporally. As expected from the data of experiment 1, young observers were better able to detect the sharp edge than were the older observers in both central and peripheral viewing conditions. For both age groups, edge detection was better during central viewing than during peripheral viewing. However, contrary to expectations based on the results of experiment 1, detection of the fuzzy edge was better for central than for peripheral viewing for both age groups in experiments 3 and 4. The apparent (and expected) equality of performance found in experiment 3 for young and elderly observers in detecting the fuzzy edge was shown to be due to the range of contrast values used. When appropriate contrast values were used in experiment 4, young observers detected fuzzy edges presented in central retina better than did elderly observers. The results of experiment 1 show sparing of the ability to process low spatial frequencies across (i) age and (ii) retinal location, and are discussed in terms of the notion of (i) models of age-related loss of visual function and (ii) cortical magnification. The results of experiments 2, 3, and 4 provide some support for the proposition that the contrast sensitivity of observers may be used to predict their performance on other visual tasks. However, consideration must be given to the influence of the nature of the psychophysical task required of observers when making such predictions.