Foveal dark adaptation, photopigment regeneration, and aging

Abstract

Foveal dark adaptation in 58 subjects and photopigment regeneration in 60 subjects from 10-78 years of age exhibit parallel slowing of recovery rate with increasing age, with significant correlation of the two functions among individuals. The data are suggestive of an initial slight decline in rate before age 50, followed by a greater decline occurring at different ages in different individuals. Longitudinal data for one subject from age 40-65 show an increase in pigment regeneration time constant consistent with this idea. Foveal sensitivity and photopigment density both decrease with increasing age and are significantly correlated among individuals, although sensitivity declines more with age than does photopigment density. In contrast to earlier proposals based upon the Rushton-Dowling equation, we found no universal constant of proportionality to relate log relative threshold to photopigment within our population.

The effect of bleach duration and age on the ERG photostress test

“…In agreement with our findings, Coile & Baker [4] also demonstrated a greater variability in the rate of adaptation of older participants compared to younger ones. The increased variability could suggest that those apparently normal individuals with prolonged time constants may be at risk of developing ARM.…”

“…The effect of age on recovery time constant in this study produced an increase of 27 seconds per decade (0.45 minutes / decade) which was comparable to the findings of Coile & Baker [4] who showed an increase of 0.21 minutes per decade. Although the relationship between age and time constants in this study can be fitted using a single linear function, it is possible that a steeper rate of change above 55 years may be present as suggested by Newsome et al [14].…”

“…The first method typically involves the use of a photoflash unit which produces a very brief but intense flash of light [3][4][5][6][7][8]. The second method is to expose the retina to a less intense but longer duration light until equilibrium is reached between photopigment bleaching and regeneration [1][2][9][10][11].…”

“…The psychophysically determined time constant of cone dark adaptation is known to be affected by age [4], with a reported increase of 0.21 minutes per decade. Therefore the second aim of this study was to investigate the effect of 4 age on the time constant of cone recovery as determined by the ERG photostress test with both bleaching techniques.…”

Photopigment optical density of the human foveola and a paradoxical senescent increase outside the fovea

“…Previous studies have reported age-related decreases in photopigment OD based on reflection densitometry (Kilbride et al, 1986;Keunen et al, 1987;Coile & Baker, 1992) and color matching (Eisner et al, 1987;Elsner et al, 1988;Swanson & Fish, 1996). Because these aging studies have been conducted with trichromats, the photopigment OD of M-and L-cones may have been confounded.…”