Ocular neovascularization. The Krill memorial lecture.

The various vascular systems of the eye can undergo new vessel formation. In this presentation, I discuss new vessel growth in the cornea, lens, iris, ciliary body, choroid, retina, and optic nerve head. No single factor can explain all cases of ocular neovascularization; instead there are multiple factors which can affect the various susceptible vessels. Among the known vasculognic factors are: inflammation and its products, a hypoxic retina diffusable factor, the "tumor angiogenic factor," and possibly an aging factor. The different ocular beds possess differing sensitivity to the various vasculogenic stimuli; the iris and choroid being most sensitive and the retina and ciliary body least sensitive to such stimuli. Retinal neovascularization requires both a biochemical factor and a diseased retinal vascular bed for its induction. Ocular neovascularization is a dynamic process which requires a persisting stimulus or else the new vessels tend to regress. The normal eye seems to possess at least two antivasculogenic agents.