Now we know that vascular endothelial growth factor (VEGF) is the major angiogenic stimulus responsible for increase of vasopermeability, cellproliferation and angiogenesis in diabetic retinopathy (DRP). Several studies, evaluating VEGF levels in vitreous, have indicated a role for VEGF in diabetic macular edema: vitreous samples of patients with diabetic macular edema contain elevated VEGF concentration and VEGF injected in experimental studies results in breakdown of the blood-retina barrier.