Photoreceptor cell death is concomitant to degeneration in the inner retina (Marc et al., 2003; Cuenca et al., 2004, 2014; Puthussery and Taylor, 2010; Jones et al., 2016), and results in progressive loss of retinal ganglion cells (García-Ayuso et al., 2010; Kolomiets et al., 2010) and decreased density of melanopsin-containing ganglion cells in late stages of retinal degeneration (Esquiva et al., 2017; Garcìa-Ayuso et al., 2015; Lax et al., 2016). This evidence concerns the gene OPN4 and retinal degeneration.