Matching range and age in a blue-green equation

Abstract

In a reanalysis of a cross-sectional study of 88 normal trichromats a high correlation was found between the proportion of blue in the Moreland (blue-green) equation and matching range width. Both increased with age, showing a marked acceleration beyond about 60 years. Similar age-related changes have been modelled for the absorbance of the crystalline lens. The close association of changes in colour match, matching range width and lens absorbance suggested that decreased retinal illumination could play a part in the age-related loss of blue-green discrimination. A calculation (accounting for the age-related changes in lens absorbance, colour match and pupil area) indicated an 8—fold reduction in retinal illuminance of the mixture field at the colour match point for the old (75 years) compared to the young (20 years). A simulation experiment, using a neutral filter to produce a similar change in retinal illuminance, yielded changes in matching range width for three normal subjects comparable to those found for the young and old groups. It was concluded that age-related changes in retinal illuminance alone were sufficient to account for the observed age-related loss in blue-green discrimination.