The effect of light history on the photolysability of human visual pigments in situ

Abstract

The foveae of two subjects were studied by the method of rapid fundus reflectometry (RFR). Difference spectra were obtained after the eye had dark-adapted for at least 12 min and then been exposed to a bleaching light of variable intensity and spectral composition. It is found that if the period of dark-adaptation is preceded by an exposure to intense light, designed to eliminate the previous light history of the retina, the density spectrum is lower than in the absence of such a clearing exposure, provided the latter is such as to furnish on average more than one quantum per visual pigment molecule within approximately 500 msec. It is shown that, within limits, cone pigments studied with RFR show properties similar to those obtained with visual purple in vitro .