Investigation of light-induced lacrimation and pupillary responses in episodic migraine

PLoS One. 2020 Oct 30;15(10):e0241490. doi: 10.1371/journal.pone.0241490. eCollection 2020.

Abstract

The purpose of this pilot study was to investigate the light-induced pupillary and lacrimation responses mediated by intrinsically photosensitive retinal ganglion cells (ipRGCs) in migraine. Ten participants with episodic migraine and normal tear production, as well as eleven visually normal controls participated in this study. Following an initial baseline trial (no light flash), participants received seven incremental and alternating red and blue light flashes. Pupillometry recording of the left eye and a 1-min anesthetized Schirmer's test of the right eye (using 0.5% proparacaine) were performed simultaneously. Intrinsic and extrinsic ipRGC photoactivities did not differ between migraine participants and controls across all intensities and wavelengths. Migraine participants, however, had significantly lower lacrimation than controls following the highest blue intensity. A positive correlation was found between melanopsin-driven post-illumination pupillary responses and lacrimation following blue stimulation in both groups. Our results show that participants with self-reported photophobia have normal ipRGC-driven responses, suggesting that photophobia and pupillary function may be mediated by distinct ipRGC circuits. The positive correlation between melanopsin-driven pupillary responses and light-induced lacrimation suggests the afferent arm of the light-induced lacrimation reflex is melanopsin-mediated and functions normally in migraine. Lastly, the reduced melanopsin-mediated lacrimation at the highest stimulus suggests the efferent arm of the lacrimation reflex is attenuated under certain conditions, which may be a harbinger of dry eye in migraine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Female
  • Humans
  • Male
  • Middle Aged
  • Migraine Disorders / diagnosis
  • Migraine Disorders / metabolism
  • Migraine Disorders / physiopathology*
  • Photic Stimulation
  • Pilot Projects
  • Pupil / physiology
  • Pupil / radiation effects
  • Retinal Ganglion Cells / metabolism
  • Retinal Ganglion Cells / pathology
  • Rod Opsins / metabolism
  • Tears / physiology*
  • Tears / radiation effects
  • Young Adult

Substances

  • Rod Opsins
  • melanopsin

Grants and funding

John and Melinda Thomson Endowment Fund for Vision Neuroscience [AMFW] Department for Ophthalmology and Vision Sciences at the Hospital for Sick Children [AMFW] The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.