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C. Clark, J. Hardy, J. Werner; Spatiotemporal Frequency Surfaces Characterizing Age–Related Changes in Scotopic Vision . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4597.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Psychophysical studies demonstrate age–related losses in contrast sensitivity to low spatial frequencies under scotopic conditions. It is not clear whether there are similar age–related losses in the scotopic temporal contrast sensitivity function (CSF) or whether there is a temporal–frequency dependence in the scotopic spatial CSF. To characterize age–related changes in scotopic vision, we measured contrast sensitivity using spatially and temporally varying sinusoidal stimuli. Methods: Spatial and temporal CSF's were measured for 15 younger (18–35 years) and 15 older (65–82) observers under scotopic conditions (–1.0 log scotopic Tds mean retinal luminance). Following 30 minutes of dark adaptation, observers viewed vertically–oriented Gabor patches of all combinations of 7 spatial (0.25 – 3.0 cpd) and 6 temporal (0.5 – 16.0 Hz) frequencies presented on a CRT monitor controlled by an 10–bit video card. A 7X astronomical telescope was used so that the stimuli could be presented with a constant number of cycles at all spatial frequencies and to control for age–related changes in pupil diameter. Ocular media density was derived from individual scotopic spectral sensitivity functions. Stimuli were presented at 10° retinal eccentricity along the vertical meridian of the superior retina. Contrast sensitivity was measured using a maximum–likelihood, 2–alternative, temporal forced–choice procedure where threshold contrast corresponded to 75% detection probability. Results: Spatial and temporal CSF's were low pass in shape for both younger and older observers; contrast sensitivity decreased with increasing spatial and temporal frequency. Older observers showed losses in contrast sensitivity relative to younger observers. These losses were especially pronounced at lower spatial and temporal frequencies, and were maintained throughout all conditions tested. Conclusions: Age–related losses in contrast sensitivity are selective for lower spatial and temporal frequencies under scotopic conditions even when the senescence of optical media is accounted for, a result critical to assessing the contributions of optical and neural factors in aging. The results suggest that there is a selective age–related sensitivity loss in mechanisms tuned to low spatial and temporal frequencies within the magnocelluar pathway.
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