Since the pioneer work of Michaelson in 1947 reporting that retinal ischemia induces the release of soluble angiogenic compounds, numerous studies have been conducted to identify the molecular structure or such messengers. In the early 1980s, the deciphering of angiogenic factor-signaling pathways and their description in the retina focused attention on growth factors. Vascular endothelial growth factor, the major candidate identified in 1992, induces in vivo angiogenesis and vascular permeability. Its expression is enhanced in vitro by hypoxia and hypoglycaemia; and its immunoreactivity is increased in diabetic patients. A decrease in its bioavailability reduces the intensity of neovascularization.