The strong correlation between the severity of the repair deficiency and the onset of photoreceptor loss, as well as the enhanced ionizing radiation hypersensitivity of photoreceptor cells of Csbm/m/Xpa−/− mice (as compared to age-matched Csbm/m animals), well support the hypothesis that (oxidative) DNA damage likely underlies the retinal degeneration. This evidence concerns the gene XPA and retinal degeneration.