The discovery of stem cells in the adult retina of mammals, located mostly to the ciliary margin, prompted investigations towards the possibility of using autologous stem cells for treating retinal disorders. In this thesis, we wanted to see if stem/progenitor cells harvested from human and rat ciliary body could be isolated, display self-renewal and form neurospheres. We also wanted to characterize the histological features of the neurospheres. Further, the thesis addresses some aspects surrounding the use of stem cells for treating retinal disorders. Cells were isolated form the pigmented ciliary epithelium in adult Brown Norwegian rats and human post-mortem biopsies, and grown using the neurosphere assay. Light microscopy was used to assess the size of the spheres. Transmission/scanning electron microscopy was used for ultrastructural analysis of the neurospheres. Our findings confirm that the ciliary body of both rats and humans harbours stem/progenitor cells, which readily divide in vitro creating neurospheres, in accordance to previous reports. The size of the produced spheres was 134±50 ?m (human) and 111±48 ?m (rat) (passage 1+10 days, mean±SD, n=45, p<0.05). The neurospheres displayed features of an in vitro stem cell niche, such as extracellular matrix and a hierarchy where the center of the sphere consist of undifferentiated cells, whereas peripheral cells are more differentiated. Reports indicate that retinal stem cells could be used to treat some of the most common retinal disorders. To collect retinal stem cells, the ciliary body seems suitable since the location favours surgical harvest and the cells are easily grown and expanded in vitro.