OPN4 and Leber hereditary optic neuropathy: Interestingly, in both LHON and DON, melanopsin-containing RGCs are spared, despite the extensive degeneration of conventional RGCs (La Morgia et al., 2011, 2010; Moura et al., 2013) as seen in FD mouse retinas (Fig. 2) (Ueki et al., 2016) and FD patients (Mendoza-Santiesteban et al., 2017).