USH2A and retinitis pigmentosa: The resulting dendrogram (Supplementary Fig. 5) captures some of the known phenotypic similarities in IRDs such as Stargardt phenocopy genes (ABCA4, PRHP2 and PROM1), retinitis pigmentosa genes (RPGR and USH2A) and achromatopsia genes (CNGA3 and CNGB3).