Flash bleaching of rhodopsin in the human retina.

1. Measurements were made of the photo-sensitivity of rhodopsin in the living human retina following bleaching with (a) a flash less than 1 msec in duration, (b) a continuous exposure lasting 30 sec.2. The apparatus consisted of a fundus reflectometer coupled to a computer for on-line processing. Three subjects were studied.3. The relations between the quantity of pigment bleached and the incident energy are so similar for the flash and continuous exposure tests that the occurrence of photo-reversal (such as has been reported in similar circumstances for visual pigment in solution) seems to be ruled out.4. Nonetheless, the two experimental conditions lead qualitatively to two different photo-chemical states in as much as the density difference spectrum for the flash exposure is displaced toward longer wave-lengths in comparison with the data obtained with the continuous exposure.5. The results are discussed with reference to the sequence of events following the bleaching of visual pigments solutions as reported by other workers.