SOD1 and retinal degeneration: It appears unlikely that H2O2 is the critical ROS target through which Cyt-b5 exerts its neuroprotective activity, since overexpression of Superoxide dismutase 1 (Sod1), which destroys superoxide radicals, decreased blue light-induced H2O2 levels but did not suppress blue light-induced retinal degeneration (Supplementary Fig. 6).