Pupil Size as an objective Biomarker for Photophobia severity in migraine

Migraine is one of the oldest reported diseases and the second most disabling disease worldwide. It affects almost 1.1 billion people worldwide and is a major cause of morbidity and disability specially in the young population. In 80 % of migraine attacks, photophobia or light sensitivity is a core component. The exact cause of photophobia in migraine is not yet known and a number of causes have been postulated like cortical hypersensitivity to light, altered ocular parasympathetic outflow, and intrinsically photosensitive retinal ganglion cell pathways acting on dura-sensitive thalamocortical neurons which in turn can influence pupillary light reflexes.

At present there is no objective biomarker for photophobia in migraine and the diagnosis solely rests on symptoms that the patient reports. If we can have a quantifiable biomarker for photophobia severity in migraine then targeted therapies for photophobia  can significantly reduce migraine related disability. In a recent study we reported that the patients of migraine with photophobia have a larger pupil size as compared to patients with no history of migraine and that the severity of headache correlates with a larger pupil size. In this study we want to check the effect of pupil size on the UPSIS 12 Utah Photophobia symptom Impact Scale which is a validated questionnaire on photophobia and to correlate the pupil sizes to the severity of photophobia in migraine patients.