OPN4 and Photophobia: <h4>Objective</h4>The aim of this study was to determine the photoreceptor basis of light avoidance in mice and assess the effect of CGRP sensitization on this behavior.<h4>Background</h4>Prior studies have suggested that photophobia is mediated by a subset of retinal ganglion cells (RGCs) that contain melanopsin, making them intrinsically photosensitive (ipRGCs).