Vascular endothelial growth factor (VEGF) protein is believed to play a critical role in angiogenesis and radiation retinopathy. It is one of the key contributors to physiological or pathological conditions that can stimulate both the formation of new blood vessels and normal vessel incompetence. Ranibizumab is a recently approved vascular endothelial growth factor (VEGF) inhibitor shown to be effective in treating exudative macular degeneration. Ranibizumab binds to and inhibits vascular endothelial growth factor A (VEGF-A), which has been shown to cause neovascularization and leakage in models of ocular angiogenesis.