The Effect of Red Light Exposure on the Pre-Existing Melanopsin-Driven Post-Illumination Pupil Response (.pdf)

Intrinsically photosensitive retinal ganglion cells (ipRGCs), the specific sub-group of retinal ganglion cells that mediate the pupillary light reflex, contain a bistable photo-pigment called melanopsin. The activation of melanopsin drives a persistent firing of ipRGCs resulting in a sustained pupil constriction after the offset of light stimulation (post-illumination pupil response, PIPR). It has been proposed that after activation by blue light, activated melanopsin is converted back to its resting state by long wavelength light exposure, a putative mechanism of melanopsin chromophore recovery in vivo. We tested this hypothesis by investigating hether red light attenuates the ongoing post-illumination pupil response (PIPR) induced by melanopsin-activating blue light.