31 Other research has established that sensitivity losses in older participants are beyond what one could predict based on reduced retinal illuminance caused by pupil miosis. 5, 7 The loss of modulation sensitivity with age is unlikely to be due to age-related changes in the temporal characteristics of neurons, as the timings of peaks in the impulse response function are relatively stable until approximately 80 years 6, 30 and the timing of multifocal ERG parameters are stable with age in the central vision (5°), although the amplitude of the response decreases. Both a shift in the peak of the temporal CSF and an overall reduction in sensitivity could produce a decrease in modulation sensitivity at a particular temporal frequency. The established limits of healthy aging may benefit from future studies in patients with ocular hypertension and/or glaucoma that are known to experience loss of flicker sensitivity.Ī number of reasons for the loss of flicker sensitivity in aging and disease have been explored. The health of the retina index captures the lowest threshold, usually obtained under photopic conditions, as well as the loss of flicker sensitivity with decreasing light level. This bilinear pattern of the change in flicker thresholds with age is consistent across photopic and mesopic light levels. Log flicker thresholds changed bilinearly with age they remained stable until 40 to 50 years, with a linear decline with increasing age. Mesopic and photopic flicker thresholds were used to calculate an index, the health of the retina index, to determine the limits of flicker sensitivity in healthy aging. Participants were excluded if they had signs/history of ocular disease, substantial interocular differences in flicker thresholds, or were unable to detect 100% flicker modulation in the high mesopic range. The background luminance ranged from 0.6 to 60 cd/m 2 and pupil size was measured continuously. Thresholds were measured for detection of 15-Hz flicker at the fovea (0°) and at an eccentricity of 4° in each of the four quadrants.
We investigated 71 participants aged 20 to 75 years.
This study aimed to establish how healthy aging of the retina affects the detection of 15-Hz flicker under photopic and mesopic lighting. In general, the effects become more significant in those older than 40 to 50 years, with increased intersubject variability and stronger dependence on ambient illumination. Aging can affect many aspects of visual performance.
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