Foveal flicker sensitivity in healthy aging eyes II Cross-sectional aging trends from 18 through 77 years of age

Abstract

Foveal flicker contrast sensitivity was measured for healthy adults at temporal frequencies from 2.5 to 50 Hz. The first experiment compared two-interval forced-choice (2IFC) and yes-no detection (Y-N) testing procedures for younger (19-33-year-old) and older (67-73-year-old) observers. The 2IFC technique resulted in higher absolute estimates of sensitivity. However, within a method, relative differences were similar. Therefore the two methods gave similar estimates of temporal contrast-sensitivity change with age. Experiment 2 compared 89 observers from 18 through 77 years of age to explore the effect of the time course of aging on flicker sensitivity. The 2IFC procedure was used, and retinal illuminance changes with age were controlled. Significant overall losses in contrast sensitivity were found for the 45-54, 55-64, and 65-77-year-old age groups. Overall sensitivities for the 35-44-year-old group were comparable with or (not significantly) higher than those for the 18-24- and 25-34-year-old groups. The results suggested that (1) foveal temporal contrast sensitivity does not decline until after 44 years, (2) losses after 44 years are in amplitude but not in temporal resolution of the visual response, and (3) the mean rate of loss is approximately 0.78 decilog per decade after 44 years. These results are consistent with the existence of three phases of development of temporal contrast sensitivity over the life span. The results also emphasize the importance of including healthy-eyed age-matched controls in studies of flicker sensitivity in visual dysfunctions that affect mainly older adults.

Impulse response of an S-cone pathway in the aging visual system

“…Psychophysical methods have been used to derive an IRF from two-pulse thresholds and from tCSFs for stimuli modulated in luminance. The two approaches agree reasonably well 1,2 and are also qualitatively consistent with earlier studies of critical flicker frequency (CFF), considering that the latter seldom took account of retinal illuminance changes in the older retina due to reductions in pupil area and lenticular transmission. 3,4 In our previous study, 2 we measured two-pulse thresholds 5 for an achromatic test patch with a spatial Gaussian shape superimposed on a 10 cd/ m 2 background having the same chromaticity as the pulse.…”

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“…More interesting, given the current context, was the finding that tIRFs of older observers consistently demonstrated reduced amplitude for the initial excitatory phase with no systematic age differences in the latency of the peak response (or zero crossing between response phases). Hence, Shinomori and Werner (2003) were able to independently confirm the previous conclusion of Kim and Mayer (1994) using an entirely different approach. It would appear, therefore, that age-related changes in flicker sensitivity are indicative of reduced contrast sensitivity within temporally tuned visual mechanisms instead of a more generalized slowing in visual processing.…”

“…Unlike Tyler's (1989) study, they failed to observe a leftward shift in the overall shape of the tCSF in their older observers and concluded that aging was characterized by a reduction in sensitivity of temporally tuned visual mechanisms rather than a generalized ''slowing'' in the rate of visual processing. Additional data analyses conducted by Kim and Mayer (1994) provided support for this interpretation of their data. According to linear systems theory, the impulse response function (IRF) quantitatively describes the response of the visual system to temporally modulated stimulus input.…”

Psychophysics, reliability, and norm values for temporal contrast sensitivity implemented on the two alternative forced choice C-Quant device

“…17 In the healthy population, the TCS as a function of age shows three phases. 19,20 The first phase, where the TCS increases, is up to an age of approximately 16 years. From 16 to 60 years, the TCS is relatively constant.…”