RHO and retinitis pigmentosa 1: With the exception of the rhodopsin gene (RHO), which accounts for approximately 25% of adRP [4], the diverse genetic basis for RP, which is caused by a number of mutations in over 100 identified genes each mutation affecting one or more photoreceptor functions, makes gene therapy to correct the primary genetic defect unrealistic until gene therapy becomes so routine that can be individualized.