Asymmetry of choroidal venous vascular patterns in the human eye

Purpose: To describe the angioarchitecture of choroidal veins in normal subjects using indocyanine green (ICG) angiography. Design: Consecutive observational case series. Participants: Thirty-six eyes of 33 healthy volunteers ranging in age from 21 to 81 years (50.0±18.2 [mean ± standard deviation]). Methods: Indocyanine green angiography was performed with a modified Topcon fundus ICG camera. Montage images were obtained during the venous phase of the ICG angiogram. Main Outcome Measures: Indocyanine green angiographic montage images covering all areas of the observable fundus. Results: Eighteen of 36 eyes examined (50%) showed asymmetry of choroidal venous vascular patterns consistent with a preferential route of choroidal venous drainage of the macular region. Twelve of the 18 eyes with a preferred drainage route drained superotemporally; the remaining 6 eyes drained by either an inferotemporal or a superonasal route. A preferential choroidal venous drainage route in the macula was identified with equal frequency in young and old subjects. Of 36 eyes examined, 27 (75%) lacked ICG angiographic evidence of symmetric separation of outer choroidal veins. Conclusions: There is ICG angiographic evidence of asymmetry of choroidal venous drainage in one half of normal individuals. The relative frequency of a resulting preferential drainage route in a group of normal subjects and the equal distribution in young and old subjects indicate that this finding is neither pathologic nor attributable to aging. There is also ICG angiographic evidence for a lack of symmetric separation in the outer choroidal venous system in the majority of normal human subjects tested, indicating that classic watershed zones may not be present or are less prominent in this portion of the choroidal vasculature.