Figure 2.

Spectral responses of pupillary constriction during exposure to continuous light. A, Pupillary light responses are shown in normally sighted individuals (n = 5; gray traces) and in a blind participant without rod and cone function (black traces). Participants were exposed to 4 min of fixed-irradiance (13 log photons cm⁻² s⁻¹) narrow-bandwidth light at eight different wavelengths. Error bars shown in light gray indicate SEM. B, Spectral responses in sighted individuals and the blind individual are shown by gray and black circles, respectively. Percentage constriction was measured during the fourth minute of light exposure and plotted by corneal irradiance. The black trace shows the best-fit Gaussian function for spectral responses in the blind individual; peak spectral sensitivity is observed in the short-wavelength portion of the visual spectrum. C, For each of the light exposures given, relative irradiance levels and spectral composition are shown.