Retinal neovascularization, collaterals, and vascular shunts.

Retinal vascular disorders are a leading cause of human visual impairment. It is only within the past decade, however, that methodologies such as fluorescein angiography (Novotny and Alvis, I96I) and retinal digestion (Kuwabara and Cogan, I960) have been developed which permit us accurately to delineate the various features of retinal vascular disease. We must remember that retinal vascular responses to abnormal situations are remarkably limited; understanding these responses will aid us in the diagnosis and management of retinal vascular disease. In our experience, we find that ophthalmologists often confuse the three entities, neovascularization, collateralization, and shunt formation. Each has a different appearance, different aetiology, and a different prognosis. We will demonstrate the significant features of each type, placing it in its proper clinical context. It is first necessary to define each entity (Table These are new vessels originating from and contiguous with the pre-existing retinal vascular bed. They are located either within or adjacent to the retina, in areas where vessels are not normally present.