The study of new speculative models of disease’s expressivity in mutant heterozygous female carriers should be considered to open a wide and strong opportunity in the gene replacement therapy for RPGR-ORF15-associated retinal degeneration, due to the fact that by silencing just the anomalous gene product one could re-establish a normally enough phenotype in the patients. This evidence concerns the gene RPGR and retinal degeneration.