Retinal degenerative diseases such as retinitis pigmentosa and age-related macular degeneration are among the leading causes of blindness in the world. These diseases are characterized by a progressive loss of photoreceptors and/or retinal pigment epithelium, leading to severe remodeling of the retinal circuitry and a gradual loss of vision. However, cells in the inner retina that connect to the brain may remain functional throughout the disease. Therefore, if the diseased cells could be bypassed or replaced with new cells that connect to the functional part of the retina, it might be possible to restore vision in affected individuals. One approach is to replace diseased cells with healthy cells through transplantation.