Therefore the differences in angiogenic potential observed between the recombinant EPOs Darbepoetin Alfa and Epoetin beta and the human cell derived Epoetin Delta in the present study may reflect a ligand-mediated modulation of the Epo receptor with differential downstream signalling outcomes and suggests that the potential risks of administering an ESA to patients with proliferative retinopathies [18], [20] may be avoided by careful choice of the EPO mimetic. This evidence concerns the gene EPO and retinal disorder.