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Relationship between Human Pupillary Light Reflex and Circadian System Status
Maria Angeles Bonmati-Carrion1, Konstanze Hild2, Cheryl Isherwood3
1Chronobiology Laboratory, Department of Physiology, Faculty of Biology, University of Murcia, IMIB-Arrixaca, 30100, Espinardo, Murcia, Spain.
Plos One
|September 17, 2016
Summary
Robust circadian rhythms correlate with reduced pupillary light reflex (PLR) under short-wavelength light. This suggests a link between circadian system health and the melanopsin-driven pupillary response, offering a new assessment tool.
Area of Science:
- Ophthalmology
- Chronobiology
- Neuroscience
Background:
- Intrinsically photosensitive retinal ganglion cells (ipRGCs) utilize melanopsin, with peak sensitivity in short wavelengths, influencing the pupillary light reflex (PLR) and circadian rhythms.
- The pupillary light reflex (PLR) is regulated by the olivary pretectal nucleus (OPN), while the suprachiasmatic nuclei (SCN) act as the primary circadian pacemaker.
- Evaluating PLR under short-wavelength light (≤500 nm) may offer indirect assessment of circadian system status.
Purpose of the Study:
- To investigate the relationship between pupillary light reflex (PLR) responses to short-wavelength light and the robustness of circadian rhythms.
- To explore the potential of an integrated PLR parameter as a tool for indirectly assessing circadian system status.
- To establish correlations between pupillary reflex parameters and established measures of circadian rhythmicity and sleep quality.
Main Methods:
- Fifteen healthy participants received nine monochromatic, photon-matched light stimuli (420-500 nm) to analyze PLR.
- Circadian status was assessed via wrist temperature (WT) and motor activity rhythms (WA), light exposure patterns (L), and questionnaires (diurnal preference, sleep quality, daytime sleepiness).
- Linear correlations were calculated between PLR parameters and a derived circadian status index (CSI).
Main Results:
- Robust circadian rhythm markers (high stability, low fragmentation, high amplitude, phase advance, low internal desynchronization) were correlated with reduced PLR at 460-490 nm wavelengths.
- An integrated circadian (CSI) and pupillary light reflex (cp-PLR) parameter was proposed and demonstrated an inverse correlation.
- These findings reveal a significant inverse relationship between circadian system robustness and pupillary reflex response to short-wavelength light.
Conclusions:
- A strong correlation exists between the robustness of circadian rhythms and the pupillary reflex response to short-wavelength light.
- The study establishes a novel link between two key non-visual functions mediated by melanopsin-ipRGC input.
- The proposed integrated parameters (CSI and cp-PLR) may serve as valuable tools for assessing circadian system health.
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