The up-regulation of VEGF has been detected in the ocular tissues of patients and animals models during the early phase of DR, serving as a microvascular permeability-promoting and proinflammatory factor in retina; moreover, VEGF is elevated in vitreous fluid of PDR patients, contributing to retinal neovascularization and macular edema in the advanced phase of the disease. The gene discussed is VEGFA; the disease is macular retinal edema.