Diabetic retinopathy exhibits characteristics of a chronic inflammatory process: increased levels of cytokines, such as IL-1β, IL-6, and TNF, have been found in the vitreous fluid of diabetic patients [161–163]; retinal TNF levels are also increased in diabetic patients, particularly in those with proliferative diabetic retinopathy [164–166]. Here, TNF is linked to proliferative diabetic retinopathy.