Mutations in the ABCA4 gene alone accounted for 34.1% of isolated IRDs, 10.3% were found in BEST1, whereas mutant alleles accounting for non-syndromic rod–cone dystrophies were found in 10.3% of the 7–17-year-old group (RP2, PRPF3, RPGR; IMPG2, PDE6B, CNGA1, MFRP, RP1). Here, RPGR is linked to respiratory distress syndrome in premature infants.