A note on the action spectrum of human rod vision

A template representing the spectral distribution of the absorption coefficients of human rhodopsin was fitted to each of 59 individual action spectra of human rod vision (from one of three populations) by an optimization routine. Curve-fitting parameters included peak wavenumber, optical density at this wavenumber and (for those from the population neither aphakic nor constrained to ages where the standard lens transmissivity curve is supposed valid), density of the latter at the wavenumber of peak lens absorption. The average peak wavenumber of each population differed significantly from that of the other two. Either the standard curve of lens absorption (even with peak lens density as a curve-fitting parameter) is inappropriate for correcting the normal spectrum or the rhodopsins in the retinas of these populations do not all have identical wave-numbers of peak absorbance.