Retinal dystrophy in the rat--a pigment epithelial disease.

Rod outer segment renewal rate was studied by autoradiographic technique in both the Wistar rat (control) and the Royal College of Surgeons (RCS) dystrophic rat. The dystrophic rat showed normal renewal rate until age 18 days, whereupon further outer segment disc movement slowed and a previously established retrograde degeneration of outer segments progressed. The dystrophic rat differed from the normal in that it showed no evidence of phagocytosis of rod outer segment material by its pigment epithelium. Argument that the primary retinal defect is at the level of the pigment epithelium is presented.