The main interest of stem cells in ophthalmology is the treatment of retinal degenerative conditions such as Retinitis Pigmentosa, Age-Related Macular Degeneration or Myopic Degeneration, and generally speaking, in all the scar-forming diseases of the retina. Stem cells are withdrawn from adult bone marrow and injected intravitreally, improving the performance of retinal cells such as photoreceptors. This is a research work that has given me four years of study to understand the behavior of stem cells in the retina. I want with this brief introduction to make available this work, wishing it to be a link between research and treatment of the retina, to try to achieve the cure of diseases that do not yet have it.