Figure 3.

The contribution of rod-cone photoreceptors and melanopsin to pupillary light responses is irradiance-dependent. Irradiance-response curves for the pupillary light reflex are shown for a continuously presented blue-light stimulus (480 nm; pupil measured from 90 to 120 s after light onset) in individuals with normal vision (blue circles, left panel) and in a blind individual with no light perception (black circles, middle panel). An overlay of the irradiance-response curves (right panel) shows reduced pupillary responses to lower-irradiance exposures in the blind individual, whereas the melanopsin-dependent response at the highest irradiances tested was comparable to sighted individuals. In each plot, the best-fit regression line is shown with 95% CIs (solid and dotted lines, respectively). Drop lines indicate the irradiance corresponding to a half-maximal pupillary constriction response. Data are replotted with permission from (38).