RPGR and retinitis pigmentosa 1: Mutations in RPGR account for 10–20% of all RP cases and 70–80% of all cases of X-linked RP (Huang et al., 2012; Megaw et al., 2015; Tsang and Sharma, 2018) with different mutations corresponding to different retinal phenotypes (Megaw et al., 2015; Charng et al., 2016; Lyraki et al., 2016).