Approximately 6% of men and 18% of women are afflicted with migraines. (Stovner et al., 2006) Over 90% of patients with migraines report a sensitivity to light (photophobia) during headaches. (Evans et al., 2008) Some migraine sufferers report that light can trigger a migraine and some have a chronic sensitivity to light (Main et al., 1997). Migraineurs are especially sensitive to non-incandescent lighting sources such as fluorescent lights, computer monitors, and gas-vapor lamps (Katz and Digre, 2016).

The pathway that mediates photophobia appears to involve intrinsically photosensitive retinal ganglion cells ("IPRGCs"; Hattar et al., 2002) and trigeminal afferents (Noseda et al., 2010; Digre and Brennan, 2012). These retinal cells do not require input from photoreceptors to be activated by light, and they have been shown to be responsible for circadian rhythm entrainment and the pupillary light reflex. As such, these cells constitute a pathway separate from that of the visual pathway (Güler et al., 2008). IPRGCs contain the chromophore melanopsin. In these cells, 480 nm light (in the blue-green portion of the visible spectrum) isomerizes melanopsin and triggers the phototransduction cascade. However, IPRGCs can also be stimulated by rods and cones. Thus, IPRGCs can be stimulated directly by 480-nm light or indirectly by any light in the visible spectrum.

In the present study, the investigators will use a neutral gray tint to decrease stimulation of the eye by all wavelengths in the visible spectrum. The investigators will compare this intervention to a thin-film spectacle coating designed to specifically block 480-nm light. The gray tint will decrease both direct and indirect stimulation of the IPRGCs by blocking all wavelengths of the visible spectrum. The 480-nm thin-film will specifically target direct stimulation of the IPRGC.

All tints and thin films will be calibrated such that the optical density, that is the overall "darkness" of all study lenses, will be the same. All study lenses will appear to have the same overall light blocking effect to study subjects. The lenses are intended to be a preventative or prophylactic treatment for chronic migraine.