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Daphné Silvestre, Angelo Arleo, Rémy Allard; Considerable age-related contrast sensitivity loss due to less efficient cones. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5921.
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© ARVO (1962-2015); The Authors (2016-present)
Contrast sensitivity declines with healthy aging due to various internal factors, but the relative impact of each factor is still elusive. The current psychophysical study used a novel noise paradigm to investigate the age-related impact of absorption rate of photons by photoreceptors, neural noise and calculation efficiency on contrast sensitivity.
The impact of these factors and optical factors on contrast sensitivity were assessed by measuring contrast thresholds with and without external noise over a wide range of spatial frequencies (0.5 to 16 cpd) and different luminance intensities (9, 91 and 9145 Td) for 20 young (mean = 26.5 years, SD = 3.79) and 20 older (mean = 75.9 years, SD = 4.30) adults. To minimize the age-related impact of ocular factors, all participants had to have a good visual acuity (≥6/7.5) and a 2.5 mm artificial pupil was used to minimize the impact of age-related miosis affecting the retinal illumination. The age-related effect of the yellowing of the lens was also minimized in a controlled condition using a red stimulus.
The age-related contrast sensitivity losses were explained by older observers absorbing considerably less photons (4x), having more neural noise (1.9x) and a lower processing efficiency (1.4x). The aging effect on optical factors was not significant.
The age-related contrast sensitivity loss was mostly due to less efficient cones absorbing four times less photons than young adults. To prevent this decline, more studies should investigate the causes of this lost in efficiency of cones (e.g. morphological changes with aging).
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Impact of the different internal factors on the age-related sensitivity loss. The age-related sensitivity loss is represented as a function of spatial frequency at high luminance intensity on the left graph and at low luminance intensities on the right graph. Each factor responsible for the aging effect is represented with a different graduation of grey. The different internal factors are the Modulation Transfer Function (MTF), which takes into account most of the optical aberrations (note that this age-related effect was not statistically significant), the calculation efficiency (CE), neural noise (e.g. spontaneous neural activity) and photon noise, which is the stochastic absorption rate of photons by photoreceptors.
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