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.(ABSTRACT TRUNCATED AT 400 WORDS)

Three experiments were conducted to examine the processes underlying the prediction of the future position of a moving target. A target moved horizontally across a computer screen at constant velocity, disappearing partway across the screen, and subjects responded when they estimated the target would have passed a point on the far side of the screen, had it continued on its path. The first experiment demonstrated that visual tracking of the target is not necessary for successful position estimation. In the second experiment, the time over which the prediction was made rather than the interval for which the target was visible, the distance over which the prediction was made, or the velocity of the target, was found to affect performance. Finally, performance was not affected when markers were placed parallel to the trajectory of the target; the presence of gratings which masked portions of the target's path did not affect subjects' performance. The previous literature suggests that the spatial interval over which predictions are made is the important variable; we find that temporal factors are the major determinants of prediction.

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We measured contrast sensitivity at three distances (330 mm, 660 mm and 4 m) with six contact lens and two multifocal spectacle corrections for presbyopia. The two spectacle corrections were D-segment bifocals and trifocals and the contact lens corrections were distance contact lens with lookover spectacles, soft progressive bifocals, soft concentric bifocals, monovision, modified monovision, and hard crescent segment bifocals. The spectacle corrections in general gave better results for the contrast sensitivity function (CSF), than did the contact lens corrections. Distance contact lenses with lookover spectacles performed best of the contact lens corrections used. However, the differences in CSF between the various contact lens corrections were small and not statistically significant.