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Harrison McAdams, Eric Kaiser, Aleksandra Igdalova, David H. Brainard, Geoffrey K. Aguirre; Migraine is associated with greater sensitivity to melanopsin and cone stimulation. Journal of Vision 2019;19(15):22. doi: https://doi.org/10.1167/19.15.22.
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Light sensitivity between headache attacks is a common symptom of migraine, but its photoreceptor basis is unknown. We measured discomfort and physiologic responses in migraineurs to cone- and melanopsin-directed stimulation (Pre-registration: https://osf.io/qjxdf/).
We are studying 40 people with migraine and inter-ictal light sensitivity (20 with aura, 20 without aura), and 20 headache-free controls (17/14/20 studied to date). Subjects view multiple, 4-second, achromatic spectral pulses that target melanopsin, the cones, or both (light flux) with varying contrast (100–400%). During and following stimulation, we measure orbicularis oculi squint (via EMG) and pupillary response, and subjects provide discomfort ratings.
People with migraine report all stimulation (cone, melanopsin, or light flux), at all contrast levels, as roughly twice as uncomfortable as do controls (for 400% contrast stimuli, on a 0–10 scale, median discomfort scores for migraineurs vs. controls were 5 vs 3 for cones, 5 vs. 2 for melanopsin, and 6 vs. 3 for light flux). Migraineurs also have increased squint in response to these stimuli (median RMS of EMG activity for migraineurs vs. controls: 1.72 vs 1.44 for cones, 1.71 vs. 1.32 for melanopsin, and 1.78 vs. 1.40 for light flux). We are currently masked as to group assignment for the pupillometry data. When pooled across groups, we find that the pupil response to melanopsin-directed stimulation is characteristically prolonged.
Migraineurs have increased sensitivity to melanopsin and cone stimulation. We expect to present at the meeting the result of our pre-registered test for group differences in the melanopsin-evoked pupil response.
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