EYS and retinitis pigmentosa 1: –8 The coding sequences of both genes are exceptionally large—EYS is 9.4 kb and USH2A is 15.6 kb—and both are essential for structural integrity and function of photoreceptors,9,10 whereas USH2A is also important for inner ear cell function and is associated with both syndromic RP (Usher syndrome) and nonsyndromic autosomal recessive RP.11