Figure 19. Strain differences in extent. Three genotypes, one wild type (WT), C57Bl/6J, and two models of retinal degeneration, IRBP^−/− and rd8, at postnatal day (P)30 and 720 were compared. Group sizes were four to five animals for each genotype at P30 and three animals for each genotype at P720. The extent in rd8 was slightly larger than in WT. The WT and the IRBP^−/− were the same at P30 or P720. However, the rd8 at P720 was significantly smaller than the rd8 at P30 or age-matched WT.