Abstract
Purpose: :
Aging causes structural changes in the retina as well as changes in the spectral absorption of the optics of the eye. The latter reduce the amount of light that reaches the retina and alter selectively its spectral composition. The purpose of this study is to first define the statistical limits of normal aging in relation to colour vision and then to detect and distinguish between optical and retinal factors that cause a significant loss of red/green (RG) and / or yellow/blue (YB) chromatic sensitivity.
Methods: :
115 subjects, age range 16-74 years (42.0 ± 17.7 yrs) were investigated. The short wavelength range optical density of the crystalline lens (ODL) and the macular pigment optical density profile (MPOD) were measured using the Macular Assessment Profile (MAP) test. RG and YB chromatic sensitivity was measured using the Colour Assessment Diagnosis (CAD) test. Four background light adaptation levels (i.e., 65, 26, 7.8 and 2.6 cd/m2) were employed and measurement of pupil size at each level provided an average measure of retinal illuminance.
Results: :
RG and YB chromatic sensitivity worsens gradually with increasing age, with more accelerated loss above 50 yrs of age. ODL values also increase significantly with age, but MPOD values remain relatively invariant. Reduction in retinal illuminance causes significant loss of both RG and YB chromatic sensitivity in all subjects. The rate of change in chromatic sensitivity with decreasing retinal illuminance is more pronounced in older subjects.
Conclusions: :
Reduction in retinal illuminance caused by changes in pupil size and increased pre-receptoral absorption of light as well as changes in the retina can contribute to loss of both RG and YB chromatic sensitivity. When equated for retinal illuminance, the rate of decrease in chromatic sensitivity with decreasing light level signal the presence of early retinal changes / disease that cause a reduction in chromatic sensitivity.
Keywords: color vision • aging • aging: visual performance