Abstract
Although it has been shown in a number of studies that scotopic vision decreases with age,1it is not clear to what proportion different factors contribute to this aging process. Changes in absorption, scatter, and reflectivity of the dioptric media, as well as changes in the pupillary aperture and more central visual pathways may all be involved to varying degrees. Pupillary dilatation in darkness does diminish with age2and has detectable effects on scotopic vision.1Senescent changes in the transmissivity of the human lens in vivo have been shown to occur3and must have effects on scotopic visibility independent of pupil size. It was considered of interest to study the effects of lens senescence on dark-adapted thresholds in a manner that was relatively independent of other aging factors. This was achieved by comparing the scotopic thresholds of normal and aphakic observers of various ages to different
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