Melanopsin hypersensitivity dominates interictal photophobia in migraine.

Affiliation

Zele AJ(1)(2), Dey A(1)(3), Adhikari P(1)(2), Feigl B(1)(3)(4).
Author information:
(1)Centre for Vision and Eye Research, Institute of Health and Biomedical Innovation, Queensland University of Technology
(QUT), Brisbane, Queensland, Australia.
(2)School of Optometry and Vision Science, Queensland University of Technology
(QUT), Brisbane, Queensland, Australia.
(3)School of Biomedical Sciences, Queensland University of Technology
(QUT), Brisbane, Australia.
(4)Queensland Eye Institute, Brisbane, Queensland, Australia.

Abstract

PURPOSE: To define the melanopsin and cone luminance retinogeniculate pathway contributions to photophobia in healthy controls and migraineurs. METHODS: Healthy controls and migraineurs were categorized according to the International Classification of Headache Disorders criteria. Photophobia was measured under full-field illumination using electromyography in response to narrowband lights spanning the melanopsin and cone luminance action spectra. Migraineurs were tested during their interictal headache-free period. Melanopsin-mediated post-illumination pupil responses quantified intrinsically photosensitive Retinal Ganglion Cell (ipRGC) function. RESULTS: A model combining the melanopsin and cone luminance action spectra best described photophobia thresholds in controls and migraineurs; melanopsin contributions were ∼1.5× greater than cone luminance. In the illumination range causing photophobia, migraineurs had lower photophobia thresholds (∼0.55 log units; p < 0.001) and higher post-illumination pupil response amplitudes (p = 0.03) than controls. CONCLUSION: Photophobia is driven by melanopsin and cone luminance inputs to the cortex via the retino-thalamocortical pathway. In migraineurs, lower photophobia thresholds reflect hypersensitivity of ipRGC and cone luminance pathways, with the larger and prolonged post-illumination pupil response amplitude indicative of a supranormal melanopsin response. Our findings inform artificial lighting strategies incorporating luminaires with low melanopsin excitation and photopic luminance to limit the lighting conditions leading to photophobia.