CLINICAL OBSERVATIONS OF progression of the retinopathy and the risk of iris neovascularization, presumably by remov-OCULAR NEOVASCULARIZATION
ing a barrier to the diffusion of angiogenic factors. 7 Conversely, ablation of ischemic ret-Intraocular neovascularization, a pathologiinas, either by panretinal laser photocoagulcal complication of many eye diseases, is the ation or cryoablation, leads to regression of leading cause of blindness in the world. In neovascularization. 8,9 early studies of retinal development, growing Taken together, these observations support vessels were noted to invade areas of newly the hypothesis that an angiogenic factor formed retina. These observations led to the released from hypoxic retina may stimulate hypothesis that a diffusible growth factor angiogenesis both locally and at a distance. In stimulated by oxygen deprivation 1,2 may induce order for such a factor to account for all of the this blood vessel growth. Similarly, in diabetic clinical observations, several requirements must retinopathy and other retinal vasculopathies, be met. The factor should be secreted and freely neovascularization of the retina, optic nerve, diffusible, so that it can stimulate vessel growth and iris, was preceded temporally and associain adjacent retinal tissue, the optic disk, or ted spatially with retinal capillary non-perdiffuse to the anterior chamber to stimulate fusion. [3][4][5] In branch retinal vein occlusion, the iris neovascularization. Presumably the factor extent of capillary non-perfusion could be corwould be mitogenic for endothelial cells, since related with the risk of development of retinal proliferation of endothelial cells is characteristic neovascularization. 6 Removal of the lens in eyes of the neovascular response. Expression of this with diabetic retinopathy increased the rate of molecule would be induced by hypoxia, or another component of ischemia, at either the mRNA, protein synthesis, or secretion level.