Figure 4. Progression of the PRA phenotype in nine RPGRIP1^−/− MLHDs an extended family with shared environment. The nine dogs shown are all RPGRIP1^−/− with shared environment and were examined three times over a 4.2 year period. PRA phenotypes over a 4.2-year period are scored according to ophthalmologic abnormalities determined by fundoscopy, menace response, PLR, and dazzle reflex. A decreasing score indicates disease progression. Animals with scores below 3 are functionally blind and were included in the PRA affected group in the association analysis. MLD2, 5, and 7 and MLD4 and 9 are siblings.