Figure 20. Strain differences in form factor. Three genotypes, one wild type (WT), C57Bl/6J, and two models of retinal degeneration were compared, IRBP^−/− and rd8, at postnatal day (P)30 and P720. Four to five animals for each genotype at P30 and three animals for each genotype at P720 were sampled and compared. At P30, neither the IRBP^−/− nor the rd8 differed significantly from the WT. The WT and the IRBP^−/− were the same at both P30 and P720. However, the rd8 at P720 had a significantly smaller form factor than rd8 or its age-matched WT did at P30.