It is possible that genetic background or environment factors could influence the onset of development of night blindness in patients with the p.(Arg373Cys) mutation in PROM1. Finally, p.(Ala164Val) and p.(Pro171Leu) mutations in RHO were found in patients S7+G.76 and 5VY+V.14, respectively. The gene discussed is PROM1; the disease is night blindness.