CRB1 and Nystagmus: For IRD genotypes, we found that genotypes that are earlier onset, affecting the posterior pole, such as RDH12, or causing widespread degeneration, such as CRB1, had a lower proportion of gradable images, as did genotypes that tend to present with secondary cataract, severe phenotypes, or high myopia, such as MYO7A, NR2E3, and CACNA1F. Achromatopsia genotypes such as CNGB3 and CNGBA3 often have nystagmus and photo aversion, which could also explain a lower proportion of gradable images in those genotypes.