VEGFA and diabetic retinopathy: As a molecular mechanism for the pathogenesis and development of diabetic retinopathy, hyperglycemia-induced intracellular metabolic disorder including the excessive activity of vascular endothelial growth factor (VEGF) in the retina, oxidative stress such as reactive oxygen species (ROS) produced both intracellularly and extracellularly, accumulation of advanced glycation end-products, and increased cytokines among others are included.