INTRACHOROIDAL MICROVASCULAR ABNORMALITY - A PREVIOUSLY UNRECOGNIZED FORM OF CHOROIDAL NEOVASCULARIZATION

PURPOSE: To evaluate the histopathologic and histochemical characteris tics of intrachoroidal microvascular abnormality, METHODS: Forty eyes obtained at autopsy from human donors ranging in age from 20 to 91 yea rs (25 diabetics, 15 nondiabetics) were analyzed. Choroids were proces sed for alkaline phosphatase flat-embedding. Vascular patterns were ex amined and analyzed before embedding and serial sectioning. RESULTS: I ntrachoroidal microvascular abnormality had the most prominent alkalin e phosphatase reaction product of choroidal vessels, These formations appeared as ameboid or cobweb-like vascular networks (area, 0.05 to 4. 6 mm(2)) in the choroidal stroma external to the choriocapillaris. The y appeared as both single or groups of formations in the posterior pol e and equatorial regions in all subjects, Intrachoroidal microvascular abnormality was found in ive subjects with diabetes: four with type I diabetes mellitus, and one with type II diabetes mellitus, One subjec t had proliferative diabetic retinopathy, three had background retinop athy, and one had no retinopathy. Intrachoroidal microvascular abnorma lity was connect ed with all levels of choroidal vasculature. Microane urysms were observed within intrachoroidal microvascular abnormality f ormations in most subjects but not in other choroidal vessels. CONCLUS IONS: Intrachoroidal microvascular abnormality is a form of intrachoro idal neovascularization. This neovascularization has features similar to intraretinal microvascular abnormalities found in diabetic subjects but seems to form independently of the status of retinopathy, The pre sence of microaneurysms in intrachoroidal microvascular abnormalities and not other choroidal vessels supports the view that aneurysms may b e aborted attempts at neovascularization.