The absence of attenuating effect of red light exposure on pre-existing melanopsin-driven post-illumination pupil response

Abstract

It has been proposed that after activation by blue light, activated melanopsin is converted back to its resting state by long wavelength red light exposure, a putative mechanism of melanopsin chromophore recovery in vivo. We tested this hypothesis by investigating whether red light attenuates the ongoing post-illumination pupil response (PIPR) induced by melanopsin-activating blue light. Pupillary light responses were tested using "Blue+Red" double flashes and "Blue Only" single flash stimuli in 10 visually normal subjects. For "Blue+Red" conditions, PIPR was induced with an intense blue flash, followed by experimental red light exposure of variable intensity and duration (Experiment 1) immediately or 9s after the offset of the blue flash (Experiment 2). For "Blue Only" conditions, only the PIPR-inducing blue stimuli were presented (reference condition). PIPR was defined as the mean pupil size from 10 to 30s (Experiment 1) and from 25 to 60s (Experiment 2) after the offset of blue light stimuli. The results showed that PIPR from "Blue+Red" conditions did not differ significantly from those of "Blue Only" conditions (p=0.55) in Experiment 1. The two stimulation conditions also did not differ in Experiment 2 (p=0.38). We therefore conclude that red light exposure does not alter the time course of PIPR induced by blue light. This finding does not support the hypothesis that long wavelength red light reverses activated melanopsin; rather it lends support to the hypothesis that the wavelengths of stimuli driving both the forward and backward reactions of melanopsin may be similar.

Binocular Summation in Postillumination Pupil Response Driven by Melanopsin-Containing Retinal Ganglion Cells

“…Past literature following the discovery of melanopsin has largely investigated direct or consensual pupillary responses as markers of photoreceptor activity. [11][12][13][14][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Accordingly, monocular photoreceptor summation of the intrinsic pathway has been found to exhibit the following properties. First, melanopsin-mediated pupillary response amplitude is a function of retinal area stimulated.…”

“…15,16 Accordingly, in recent literature, retina-driven pupil response dynamics of the human eye have been evaluated as follows: (1) stimulation of a dilated eye and PLR recording of the fellow eye, (2) stimulation of an undilated eye and PLR recording of the fellow eye or (3) stimulation and PLR recording of the same eye. [11][12][13][14][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] The presence of binocular summation of the PLR has been well established and evaluated across rod-dominated scotopic and cone-dominated photopic luminance ranges. [33][34][35][36] Nonhuman primate models have also been used to investigate the characteristics and neural substrates of the PLR in greater detail, [37][38][39][40] and similarly report the presence of binocular summation.…”

The Relation Between Light-Induced Lacrimation and the Melanopsin-Driven Postillumination Pupil Response

“…As an initial step to evaluate the utility of light-induced lacrimation as an objective index for patients with photophobia, we sought to determine whether this reflex is indeed a melanopsin-driven response from two well-established unique photosensing properties of melanopsin: first, it has a narrow spectral sensitivity peaking at approximately 470 nm (blue light), 17 and second, once melanopsin is activated, it drives a prolonged depolarizing after-potential of the ipRGCs, leading to a sustained pupil constriction after the offset of light stimulation, 12,18 that is, the postillumination pupil response (PIPR). We hypothesized that if light-induced reflex lacrimation is melanopsin driven, the amount of tear production would be positively correlated with the PIPR induced by increasing blue light stimulation, but not with that induced by melanopsinsilent red light stimulation.…”

Dataset of red light induced pupil constriction superimposed on post-illumination pupil response

“…Study participants, testing protocols and data analysis method were described in the associated research article [1] . The chromatic pupillometry apparatus setup has also been previously described in detail [2] , [3] .…”