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Cone pigment density difference refers to a change in light absorption by cones before and after bleaching of their visual pigments. With a television ophthalmoscope image processor, we measured the foveal cone pigment density difference in patients with retinitis pigmentosa (RP), good central vision, and no clinically apparent foveal lesion. Foveal(More)
The contrast sensitivity function provides a more comprehensive and sensitive measure of spatial vision than does visual acuity. A large-sample study of contrast sensitivity during the adult years revealed that observers over age 60 have a substantial loss of sensitivity to intermediate and high frequencies. All observers wore their best possible optical(More)
Contrast sensitivity functions (CSFs) were measured for two groups of healthy observers, a younger group with mean age 18.5 years and an older group with mean age 73 years. Although the two groups had virtually identical sensitivities to high spatial frequencies (gratings with narrow bars), the younger observers were three times more sensitive at low and(More)
The first paper in this series suggested that, in order to see gratings of low spatial frequency, observers in their 70s needed three times as much contrast as did observers in their 20s. Here, we use a signal detection procedure to determine if this age difference was due to actual changes in vision with age or was merely an artifact of changes in criteria(More)
Using fundus reflectometry, we have measured a decrease in the density difference of the foveal cone visual pigments with age in human subjects. This decrease is consistent with a loss of visual pigment in the retina with age. Fundus reflectance and normalized density difference spectra data are presented for these subjects. A decrease in cone pigment with(More)
The ability to see spatial structures of a wide range of sizes was measured for two groups of observers (mean ages, 18 and 73 years). All observers had good visual acuity. Although older and younger observers did not differ in ability to see targets with fine structure (high spatial frequencies), older observers were only one-third as sensitive to targets(More)
To determine the relationship of foveal absolute thresholds to visual acuity in retinitis pigmentosa, we measured thresholds in 40 patients with various forms of retinitis pigmentosa (including Usher's syndrome) whose Snellen visual acuities were 20/30 or better. At all visual acuity levels, the patients' foveal thresholds were significantly higher than(More)
The authors measured dark-adapted foveal spectral sensitivity functions in 30 patients with retinitis pigmentosa or Usher's syndrome, whose Snellen visual acuities were 20/30 or better. An analysis of variance of the spectral sensitivity functions (normalized at 575 nm) indicated a significant reduction in the patients' relative sensitivity at 450 and 475(More)
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