We re-examined 75 of 94 families with negative results by TGS (Figure 2c) using WES, which revealed genetic alterations in 28 probands (37.3%) in 17 RP-causing and five IRD-causing genes, and USH2A (N = 3, 4.0%) was found to be the most common causative gene. This evidence concerns the gene USH2A and retinitis pigmentosa 1.