Severe blinding retinal degenerative diseases have been without treatments that could improve vision until recently. Gene therapy has been in clinical trials for certain inherited retinopathies in which photoreceptors are retained despite severe visual loss. Optogenetics is being discussed for retinal diseases in which there is severe visual loss and nearly complete photoreceptor cell death. As a retinal therapy, optogenetics would be the genetic targeting of light-sensing molecules to residual cells in a degenerate retina. Parallel with scientific advances in optogenetics should be the development of detailed criteria for patient candidacy. Here, molecularly defined retinal degenerations are used to exemplify how some diseases or stages of disease would satisfy the criteria. Measurements are made of the thickness of ganglion cell and the nerve fiber layers of the retina. Whereas the clinical category of retinitis pigmentosa has been most often mentioned for treatment by optogenetics, an argument is made for expanding the target diseases to some early-onset disorders diagnosed as Leber congenital amaurosis.