The density of human rhodopsin in the rods.

The density of human rhodopsin in the rods has been estimated psych~hysically by following the change in the relative quantum sensitivity for rod vision at two wavelengths (one near the peak, the other far off on the long wave tail of the action spectrum) in the dark after a full rhodopsin bleach in a region of a typical R‘~ monochromat’s retina where cones make no contribution to threshold. Metameric matching and dark adaptation curves yield results (about 0.75 In units at 500 nm) consistent with recent densitometric estimates of Alpern and Pugh (1974) made on the normal retina.