Erythropoietin and the erythropoietin receptor (EPOR) are widely expressed within retinal cells, and several groups have tested the ability of exogenous EPO to ameliorate retinal degeneration associated in animal models of diabetic retinopathy, retinitis pigmentosa, and other forms of retinal degeneration [22,32]. This evidence concerns the gene EPOR and diabetic retinopathy.