Some studies have recently shown that the concentration of erythropoietin in the vitreous humor of diabetic patients suffering from diabetic retinopathy is higher than non-diabetic patients. It was reported a higher concentration of erythropoietin in vitreous humor than blood, indicating a local production. In some cases it was also found a positive association between concentrations of Erythropoietin and Vascular Endothelial Growth Factor (VEGF). Both of these factors, erythropoietin and VEGF, show important angiogenic activity and may play a role in the development of diabetic retinopathy.