Specifically, Matsui et al. included only subjects with non-syndromic retinal degenerations, while Grondahl et al. analyzed only four genes (RHO, RP1, PRPH2 and IMPDH1) that did not comprise USH2A. Our cohort can be directly compared to the study of Comander et al. which recruited 45 cases with pericentral RP without excluding syndromic forms [4]. The gene discussed is IMPDH1; the disease is retinitis pigmentosa 1.