Retinal photoreceptor cell degeneration in the Outer Nuclear Layer of the retina, is a common cause of blinding conditions such as Retinitis Pigmentosa, that to date, have no effective treatment. Our research focuses on examining the effect of injection of human retinal progenitor cells (hRPC) into the vitreous cavity of inflicted rat retina. We hypothesize that the hRPC will have therapeutic effects on the retina by salvaging photoreceptor cells that would have otherwise degenerated. We used the animal model RCS (Royal Collagen of Surgeons) rats as subjects, which exhibit a heritable gene mutation responsible for retinal cell degeneration. These rats were injected with hRPC inside the cavity of the eye on postnatal day 30. On postnatal day 90 (two months later), we examined the effects of hRPC on the Outer Nuclear Layer. Sections of treated retina were labeled using immunohistochemical. (anti-human antibody) to identify injected cells and the nuclear stains Hemotoxylin and Eosin to quantify the remaining photoreceptor nuclei.  Untreated subjects showed the most photoreceptor degeneration by postnatal day 90. However, our preliminary data suggest a slowing of the progression of cell death with the presence of hRPC. Thus, a hRPC injection into the eye cavity may be an effective therapy for the treatment of Retinitis Pigmentosa.