Figure 5.

Melanopsin-dependent pupillary responses are slower than rod/cone-dependent responses. (A) Representative pupillary light responses are shown for a sighted individual and a blind individual without rod and cone function. The pupil in the blind individual responded slowly after light onset and light offset, indicating that outer retinal photoreceptors are necessary for the phasic component of the pupillary light reflex. (B) In sighted individuals, the pupil could track an intermittent light stimulus (480 nm, 13 log photons/cm²/s) with alternating periods of light and darkness (5 s of light, 5 s of darkness). By comparison, the pupil in the blind individual was unable to track the intermittent stimulus. Rather, the melanopsin-dependent pupillary response increased across several light pulses until reaching a steady response. Data are replotted with permission from (38).