However, APOE-metformin treated animals had reduced photoreceptor response relative to WT-metformin treated animals (Figure 1G; p < 0.05 for treatment indicated by *), predominantly because metformin treatment was found to enhance rod photoreceptor function in WT-mice compared with WT-controls, suggesting slowing of retinal degeneration with age (p < 0.05 for treatment indicated by #). This evidence concerns the gene APOE and retinal degeneration.