CHORIOCAPILLARY CHANGES AND HYPERFLUORESCENCE ON INDOCYANINE GREEN ANGIOGRAPHY

Background: The purpose of this study is to examine the relationship b etween pathological changes of the choriocapillaris (CC) and the findi ng of bright fluorescence on indocyanine green (ICG) angiography. Meth ods: An animal model was used, with chorioretinal lesions produced by injecting sodium iodate 3 h, 24 h, 7 days or 14 days previously. The I CG angiographic findings were compared with histology. Results: Three hours after injection, many spots of bright fluorescence were scattere d at the posterior pole. Histologically, variable changes in CC endoth elial cells were observed. In some regions, the cells remained almost normal morphologically. In other regions, the endothelial cytoplasm wa s thickened with decreased fenestrations, or precipitation of fibrin I n the choroidal interstitium was observed. Twenty-four hours after inj ection, the area of bright fluorescence had extended beyond that obser ved after 3 h. Histologically, the cytoplasmic structure of CC endothe lial cells was unclear, and the endothelial walls were detached from t he 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 e ndothelial cells was thinned, but contained few fenestrations. The end othelial walls were detached from the basement membrane. Fourteen days after injection, normal diffuse ICG fluorescence was observed. Histol ogically, CC endothelial cells exhibited almost normal structure. Conc lusion: These findings indicate that changes in CC endothelial cells a nd bright fluorescence on ICG angiography are closely related. ICG ang iography should enable clinical evaluation of increased permeability o f CC endothelial cells to relatively large molecules.