Abstract
Long-term chromatic adaptation has been demonstrated in adults (Kohler, 1951; Neitz, 2002; Delahunt et al., 2004). Monochromatic unique yellow settings, for example, change as a result of long-term exposure to a chromatically altered environment (Neitz, 2002). The mechanism for the long-term perceptual change, however, is not well-understood. In the present investigation, we tested the proposal that the cone weights of the red-green mechanisms can be altered. If so, the slopes of the red and green mechanism threshold contours, which are determined by the cone weights, should change also. We examined threshold level detection contours before and after adaptation, as well as monochromatic unique yellow settings. Adaptation involved wearing red-tinted contact lenses for at least five hours each day for at least two weeks. The psychophysical measurements were done in the morning before inserting the lenses to ensure we were studying long-term changes. Unique yellow settings, which served to gauge the degree of adaptation, were measured almost daily with a monochrometer. Detection contours in the (ΔL/L, ΔM/M) plane and were measured with a CRT on a white background, before adaptation (baseline) and at the apex of the adaptation stage. In three of four cases studied so far, some change in unique yellow was found. Current data cannot support the claim that a change in red or green cone weights accounts for the shift in unique yellow.