OPN4 and Photophobia: Alternatively, melanopsin-expressing trigeminal afferent fibers in the conjunctiva, cornea, sclera, and/or uvea may transmit pain signals that contribute to photophobia (Matynia et al., 2015), and/or the pain-modulating neurons of the ventromedial raphe nucleus of the medulla may increase their pro-pain responses to their visual input (Martenson et al., 2016), thereby resulting in the enhanced light aversion we observed after impact TBI.