September 2017
Volume 17, Issue 10
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2017
Circadian and fatigue effects on the dynamics of the pupillary light reflex
Author Affiliations
  • Terence Tyson
    Human Systems Integration Division, NASA Ames Research Center
    Department of Industrial and Systems Engineering, Charles W. Davidson College of Engineering, San Jose State University
  • Erin Flynn-Evans
    Human Systems Integration Division, NASA Ames Research Center
  • Leland Stone
    Human Systems Integration Division, NASA Ames Research Center
Journal of Vision August 2017, Vol.17, 660. doi:10.1167/17.10.660
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      Terence Tyson, Erin Flynn-Evans, Leland Stone; Circadian and fatigue effects on the dynamics of the pupillary light reflex. Journal of Vision 2017;17(10):660. doi: 10.1167/17.10.660.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

The pupillary light reflex (PLR) is known to be driven by the photo-entrainment of intrinsically-photosensitive retinal ganglion cells. These ganglion cells are known to have retino-hypothalamic projections to the suprachiasmatic nuclei (SCN), which regulates circadian rhythms, and bilateral retinal projections to the pretectal area, which mediates the PLR (Dacey et al., 2005; Hattar et al., 2002, 2006). The magnitude of the PLR has previously been shown to show circadian variation (Münch et al., 2012). In this study, we used a constant routine protocol (Mills et al., 1978) to examine circadian and fatigue effects on the dynamics of the PLR. We characterized the PLR (pupil size as a function of time) in response to a square-wave change in the luminance of a white display background, at ten different times over a single circadian cycle. Twelve subjects participated in three "daytime" baseline runs followed by 7 "nighttime" runs each separated by an hour (17 – 23 hours after awakening). The constriction and dilation phases of the PLR waveform were fit separately with a single exponential model (Longtin & Milton, 1988; Milton & Longtin, 1990) with time constants estimated using a least-squares method. The dilation time constant exhibited a distinct sinusoidal modulation across the circadian cycle and, after 23 hours of wakefulness, decreased on average by 82 ms (paired t-test, p < 0.05) relative to baseline (mean: 543 ms). The constriction time constant however, did not show an overall decrease with increased wakefulness. We conclude that the dynamics of the PLR show circadian variation and that, in addition, the briskness of the dilation response to a step-decrease in luminance shows a homeostatic enhancement with increased wakefulness.

Meeting abstract presented at VSS 2017

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