RD3 and Blindness: Null mutations in GUCY2D or RD3 causative of the Lebers Congenital Amaurosis (LCA) form of blindness, for instance, would result in reduced levels of cGMP at the rod outer segments, the closure of cGMP-channels and hyperpolarization of the cell, with the ensuing reduction in the influx of Ca2+ to rod inner segment [36], [37], [41].