Summary
This study reveals that the melanopsin-driven post-illumination pupil response (PIPR) follows an intrinsic circadian rhythm in humans, independent of external light cues, with minimum ipRGC response occurring after melatonin onset. For lighting designers, this suggests that the effectiveness of circadian light stimuli targeting ipRGCs may vary predictably across the day, with implications for timing of light interventions.
Key Findings
- ipRGC-driven post-illumination pupil response (PIPR) shows a measurable circadian rhythm under constant dim illumination (10 lux) across a 24-hour period in 11 healthy young adults (18–30 years).
- Circadian variation in ipRGC activity precedes dim-light melatonin onset (DLMO), with minimum PIPR occurring post-melatonin onset.
- Outer retinal (cone) contributions to the ipRGC-driven PIPR also showed circadian variation, while direct cone inputs to the pupil light reflex did not, confirming melanopsin as the mediator of this circadian modulation.
Categories
The Science of Light: Directly investigates ipRGC and melanopsin contributions to the post-illumination pupil response (PIPR) and its intrinsic circadian rhythm.
Sleep & Circadian Health: Demonstrates that ipRGC-driven circadian variation precedes melatonin onset and is modulated across the 24-hour cycle, with implications for light entrainment.
Author(s)
EL Markwell
Publication Year
2011
Related Publications
The Science of Light
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- Diminished pupillary light reflex at high irradiances in melanopsin-knockout mice
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Sleep & Circadian Health
- Phototransduction by retinal ganglion cells that set the circadian clock
- The mammalian circadian timing system: organization and coordination of central and peripheral clocks
- The two‐process model of sleep regulation: a reappraisal
- Melanopsin is required for non-image-forming photic responses in blind mice
- Strange vision: ganglion cells as circadian photoreceptors