USH2A and autosomal recessive retinitis pigmentosa: A considerable number of autosomal recessive retinitis pigmentosa (arRP; MIM#268000) or Usher syndrome type II (USH2, MIM#276901) patients are due to USH2A gene defects, and there is an incomplete understanding of the USH2A-related inherited retinal disease (USH2A-IRD) genotype spectrum, which reduces the use of future gene therapy and optimal genetic counseling.