It has been shown that rhodopsin expression is reduced in P23H-1 transgenic rats from at least postnatal day 30 (P30) and rod degeneration starts as early as P16.30, 36 Similarly, OS length is decreased by 40% in P40 P23H-1 animals,30 and retinal sensitivity correlates with OS length in human RP patients,37 suggesting that changes in the OS might precede and predict photoreceptor cell loss. The gene discussed is RHO; the disease is retinitis pigmentosa 1.