Abstract

By adapting the eye of a normal trichromat to yellow light one can measure the sensitivity of the short wavelength sensitive (S or blue) cones. If the yellow field is turned off, the S cone mechanism does not immediately gain sensitivity as one might predict, but sensitivity is paradoxically lost. This temporary sensitivity loss is termed transient tritanopia (Mollon & Polden, 1975). The phenomenon is thought to result from the polarizing effect of the yellow field at an opponent site in the S cone pathway. Acting also on this opponent site is a "restoring force" which opposes the yellow field's effect in order to minimize polarization and thus maintain sensitivity in the S cone pathway (sensitivity is assumed to be highest when the opponent site is unpolarized). When the yellow field is decremented, signals from both M and L cones are suddenly reduced and this in turn reduces the polarizing force to the opponent site. The restoring force is now left unopposed and it continues to act for several seconds, repolarizing the opponent site and leading to transient tritanopia (Pugh & Mollon, 1979).

© 1990 Optical Society of America