OPN4 and glaucoma: Different studies showed changes in the melanopsin function of the ipRGCs not only in inner retina disorders such as glaucoma (Kelbsch et al., 2016) and ischemic optic neuropathy (Herbst et al., 2013) but also in outer retina diseases such as diabetic retinopathy (Obara et al., 2017), and early and late AMD (Maynard et al., 2015, 2017).