NONINVASIVE VISUALIZATION OF THE CHORIOCAPILLARIS AND ITS DYNAMIC FILLING

Purpose. The choroidal microvasculature and its circulation are inadeq uately assessed by presently available techniques. Laser-targeted deli very was applied to generate local, repetitive angiograms of the chori ocapillaris in primates.Methods. Carboxyfluorescein was encapsulated i n heat-sensitive liposomes and injected intravenously in monkeys. The liposome contents were then released locally in the choroid by applica tion of a short heat pulse provided by an infrared laser. The bolus of dye spread rapidly downstream from the underlying arterioles into clu sters of lobules. Video angiograms were generated with excitation illu mination provided by an argon laser. Results. Laser-targeted delivery choroidal angiography performed on three monkeys indicated that the fl uorescence was emitted mainly from the choriocapillaris. Clusters of i rregular shape with well-defined margins were observed. Adjacent arter ies typically supplied separate clusters that fit together like a jigs aw puzzle. The dynamic filling and emptying patterns, recorded at vide o rate, revealed that macular lobules were filled by a central arterio le and drained by a venous annulus. The average dye transit time throu gh a lobule (n = 10) was 118 +/- 26 msec (mean +/- SD), and the dye tr ansit velocity was 2.53 +/- 0.55 mm/sec. Conclusions. This study clear ly documents the segmental nature of the primate choroidal microvascul ature. It also illustrates that choroidal angiography by laser-targete d dye delivery provides information useful for studying the response o f the choriocapillaris to physiological and pathologic changes.