Reply: Pupil area and photopigment spectral sensitivity are relevant to study of migraine photophobia.

Abstract

Sir, Recently, we reported that green light exacerbates migraine headache significantly less than white, blue, amber or red lights in migraine patients with normal eyesight; that their light-adapted flash electroretinography (ERG) a-wave amplitude is significantly larger in response to blue than all other colours; that their light-adapted flickering ERG a-wave is significantly smaller in response to green than blue and red, and significantly smaller in response to red than blue; and that their P2 visual evoked potential (VEP) wave is smaller in response to green than in response to blue, red or amber lights. Based on the findings, we proposed that cone-driven retinal pathways might be at the origin of this colour-selective migraine-type photophobia (Noseda et al. , 2016). In a Letter to the Editor, Dr Omar Mahroo (2016) raises the possibility that our results were secondary to the effects different colours of light might have on pupil diameter. According to this scenario, a wavelength (colour) that causes the pupil to constrict more will allow less light to reach the retina and consequently will produce less pain, smaller ERG and smaller VEP, and vice versa, a wavelength that causes the pupil to constrict less will allow more light to reach the retina and consequently will produce more pain, larger ERG …