Choriocapillary changes and hyperfluorescence on indocyanine green angiography

Abstract

The purpose of this study is to examine the relationship between pathological changes of the choriocapillaris (CC) and the finding of bright fluorescence on indocyanine green (ICG) angiography. An animal model was used, with chorioretinal lesions produced by injecting sodium iodate 3 h, 24 h, 7 days or 14 days previously. The ICG angiographic findings were compared with histology. Three hours after injection, many spots of bright fluorescence were scattered at the posterior pole. Histologically, variable changes in CC endothelial cells were observed. In some regions, the cells remained almost normal morphologically. In other regions, the endothelial cytoplasm was thickened with decreased fenestrations, or precipitation of fibrin in the choroidal interstitium was observed. Twenty-four hours after injection, the area of bright fluorescence had extended beyond that observed after 3 h. Histologically, the cytoplasmic structure of CC endothelial cells was unclear, and the endothelial walls were detached from the basement membrane. When ferritin was administered as a tracer, many ferritin granules were observed in Bruch's membrane. Seven days after injection, the degree of bright fluorescence was reduced as compared with 3 and 24 h after injection. Histologically, the cytoplasm of CC endothelial cells was thinned, but contained few fenestrations. The endothelial walls were detached from the basement membrane. Fourteen days after injection, normal diffuse ICG fluorescence was observed. Histologically, CC endothelial cells exhibited almost normal structure. These findings indicate that changes in CC endothelial cells and bright fluorescence on ICG angiography are closely related. ICG angiography should enable clinical evaluation of increased permeability of CC endothelial cells to relatively large molecules.