Age-related changes in wavelength discrimination

Wavelength discrimination functions (420 to 620-650 nm) were measured for f our younger (mean 30.9 years) and four older (mean 72.5 years) observers. S timuli consisted of individually determined isoluminant monochromatic light s (10 Td) presented in each half of a 2 degrees circular bipartite field wi th use of a Maxwellian-view optical system. A spatial two-alternative force d-choice method was used in combination with a staircase procedure to deter mine discrimination thresholds across the spectrum. Small but consistent el evations in discrimination thresholds were found for older compared with yo unger observers. Because the retinal illuminance of the stimuli was equated across all observers, these age-related losses in discrimination are attri butable to neural changes. Analyses of these data reveal a significant chan ge in Weber fraction across adulthood for a chromatically opponent pathway receiving primarily antagonistic signals from middle-wavelength-sensitive a nd long-wavelength-sensitive cones but not for a short-wavelength-sensitive cone pathway. (C) 2001 Optical Society of America. OCIS codes: 330.1690, 3 30.1720, 330.4060, 330.5510, 330.6180.