Characteristics and classification of surgically-excised choroidal neovascular membranes

Purpose This study was undertaken in order to histologically characterize surgically-excised choroidal neovascular membranes and to correlate theses histologic findings with the fundus and fluorescein angiographic appearance. Material and Methods Surgically-excised subfoveal choroidal neovascular membranes submitted in the time period from November 1994 to July 1996 were included in this study. The membranes were processed and evaluated by light and transmission electron microscopy. Some membranes were oriented by the surgeon and marked on their inner surface with India ink and the configurations of these membranes were recorded and correlated with the fundus and fluorescein angiographic features. Results Sixty-two choroidal neovascular membranes were available for this study. In 74% age-related macular degeneration was the underlying disease. Retinal pigment epithelium and endothelial lined vascular channels were present in over 87,5% of cases. Basal laminar (linear) deposit was only present in membranes excised from patients with age-related macular degeneration. In six cases with Gass Type II choroidal neovascular membranes the histologic-clinical-fluorescein angiographic correlation showed well-defined (classic) neovascular membranes according to the criteria of the Macular Photocoagulation Study. Two membranes were not surrounded by retinal pigment epithelium and were classified as Type IIa membranes. Four membranes were surrounded by retinal pigment epithelium and classified as Type IIb membranes. Conclusions Choroidal neovascular membranes represent a stereotypic, non-specific wound repair response to a specific stimulus. Retinal pigment epithelium may proliferate around and attempt to wall off choroidal neovascular membranes. We propose a new classification of surgically-excised choroidal neovascular membranes as Types I, IIa, and IIb.