Adjusting to a sudden “aging” of the lens

Abstract

Color perception is known to remain largely stable across the lifespan despite the pronounced changes in sensitivity from factors such as the progressive brunescence of the lens. However, the mechanisms and timescales controlling these compensatory adjustments are still poorly understood. In a series of experiments, we tracked adaptation in observers after introducing a sudden change in lens density by having observers wear glasses with yellow filters that approximated the average spectral transmittance of a 70-year-old lens. Individuals were young adults and wore the glasses for 5 days for 8 h per day while engaged in their normal activities. Achromatic settings were measured on a CRT before and after each daily exposure with the lenses on and off, and were preceded by 5 min of dark adaptation to control for short-term chromatic adaptation. During each day, there was a large shift in the white settings consistent with a partial compensation for the added lens density. However, there was little to no evidence of an afterimage at the end of each daily session, and participants’ perceptual nulls were roughly aligned with the nulls for short-term chromatic adaptation, suggesting a rapid renormalization when the lenses were removed. The long-term drift was also extinguished by brief exposure to a white adapting field. The results point to distinct timescales and potentially distinct mechanisms compensating for changes in the chromatic sensitivity of the observer.

Fig. 1

Measured transmittance of the lenses worn by observers, compared to estimates of the average transmittance of the crystalline lens for observers of different ages (from [1]).

Fig. 2

Achromatic settings with lenses on or off, prior to adaptation to the lenses. Points plot the chromaticities of the white settings fo test stimulus in the dark context without (squares) or with (triangles) glasses; circles show the settings with glasses and room lights on. Star shows the chromaticity of the monitor white point through the glasses (filled). Black symbols represent the means across 3 observers, gray to white symbols represent individual observers.

Fig. 3

Achromatic settings at the beginning and end of each day and before or after removing the lenses. Settings are averaged across the 5 days. a) Individual settings for each observers. b) Settings averaged across all six observers.

Fig. 4

White settings with or without the lenses at the beginning and end of each day, averaged across observers.

Fig. 5

Shifts in white settings within each day (relative to the morning setting without lenses). Individual plots show the settings for different observers averaged across the 5 test days.

Fig. 6

Same settings as figure 5, but averaged across observers to show the buildup of adaptation within each of the 5 days.

Fig. 7

Dark-adapted achromatic setting (dashed line) and white settings in the presence of different adapting levels (contrast along the blue/yellow axis). Panels show settings with or without the glasses on for one observer.

Fig. 8

Short-term adaptation settings for two additional observers, plotted relative to their dark-adapted settings at the end of the day, with lenses on.

Fig. 9

Adaptation settings for 4 observers averaged across their 6 settings. Bars show the mean dark-adapted settings with the glasses on at the beginning (0 hours) or end (8 hours) of the day, the settings while adapted to the Illuminant E chromaticity on the screen (adapt to white), and then the settings after 5-minutes of readaptation to dark (de-adapt). Error bars represent the standard error of the means.