Anatomical and functional choroidal lobuli.

The purpose of this paper is to clarify the controversy between anatomists and clinicians regarding the choroidal angioarchitecture. Vascular casts from 36 human and 10 Rhesus monkey eyes were studied using scanning electron microscopy (SEM). Both the human and monkey choriocapillaris (CC) are non-homogenous structures. They have patterns which change from the peripapillary to peripheral areas. Anatomically, the 'lobular' appearance of the CC exists only in part of the posterior pole. One or more collecting venules were found in the center of 86% of the anatomical lobules, while a central feeding arteriole was observed in 14%. Both major and minor feeding arterioles supply the CC areas which may be recognized as the choroidal functional vascular unit (CFVU) or functional lobule described in the past by Hayreh. Our vascular casts and SEM study show that the choroidal anatomical lobuli are not identical with those observed by angiographical study. Thus, two distinct models of choroidal lobuli, anatomical and functional, should be recognized. The CFVU seen on fluorescein (FA) and indocyanine green (ICG) angiographies as a lobular appearance is most likely caused by the pressure gradient of the blood flow.