Melanopsin- and L-cone–induced pupil constriction is inhibited by S- and M-cones in humans

Abstract

The human retina contains five photoreceptor types: rods; short (S)-, mid (M)-, and long (L)-wavelength–sensitive cones; and melanopsin-expressing ganglion cells. Recently, it has been shown that selective increments in M-cone activation are paradoxically perceived as brightness decrements, as opposed to L-cone increments. Here we show that similar effects are also observed in the pupillary light response, whereby M-cone or S-cone increments lead to pupil dilation whereas L-cone or melanopic illuminance increments resulted in pupil constriction. Additionally, intermittent photoreceptor activation increased pupil constriction over a 30-min interval. Modulation of L-cone or melanopic illuminance within the 0.25–4-Hz frequency range resulted in more sustained pupillary constriction than light of constant intensity. Opposite results were found for S-cone and M-cone modulations (2 Hz), mirroring the dichotomy observed in the transient responses. The transient and sustained pupillary light responses therefore suggest that S- and M-cones provide inhibitory input to the pupillary control system when selectively activated, whereas L-cones and melanopsin response fulfill an excitatory role. These findings provide insight into functional networks in the human retina and the effect of color-coding in nonvisual responses to light, and imply that nonvisual and visual brightness discrimination may share a common pathway that starts in the retina.

Assessment of visual fatigue under LED tunable white light with different blue components

“…It was obvious that the illuminance increment of S cones was more significant than melanopsin, which implies that visual discomfort is primarily related to S‐cone illuminance. According to the study of Woelders et al, activating melanopsin constricted the pupil, while S‐cone activation dilated the pupil. Therefore, increased illuminance of S cones could lead to increased pupil size.…”

“…The photoreceptor‐specific illuminance of experimental lighting conditions calculated based on Lucas et al…”

“…Light exposure has a great neurobiological effect on humans such as pupil constriction and brain cognition . The intensity, timing, duration, and spectral characteristics of light all contribute to these effects .…”

“…Recent studies also showed that M‐cone or S‐cone illuminance increments led to pupil dilation, whereas L‐cone or melanopsin illuminance increments resulted in pupil constriction. This suggests that the contributions of different photoreceptors to human physiology are different . Thus, it is important to characterize the spectrum using photoreceptor‐specific illuminance in terms of photobiology effects.…”

“…Light exposure has a great neurobiological effect on humans such as pupil constriction and brain cognition. [1][2][3] The intensity, timing, duration, and spectral characteristics of light all contribute to these effects. 4 However, the related mechanism is still unclear, particularly the spectral influence on the neurobiological system.…”