Topographic variation of the choroidal watershed zone and its relationship to neovascularization in patients with age-related macular degeneration

Abstract

Purpose: To evaluate the patterns of choroidal watershed zones (WZs) in exudative age-related macular degeneration (AMD) and to describe their relationship with choroidal neovascularization (CNV).

Methods: We retrospectively evaluated 50 digital indocyanine green video-angiograms of 50 patients with exudative AMD demonstrating one or more WZs. In addition, the relationship between the site of CNV and the WZ was analysed.

Results: A stellate WZ was observed in 30 of 50 (60%) patients. Choroidal neovascularization occurred within the centre of the WZ in all cases. The WZ was vertically oriented in 18 of 50 (36%) patients. When the WZ coursed through or extended into the fovea, CNV occurred within the WZ, but it occurred at its margin when the WZ did not involve the fovea. An angled WZ coursing through the fovea with CNV occurring within it was observed in two of 50 (4%) patients.

Conclusions: In exudative AMD, the WZ most commonly conformed to the stellate pattern, followed by the vertical and angled patterns. Choroidal neovascularization occurred within the WZ in 44 of 50 (88%) patients. When the WZ did not involve the fovea (12%), CNV occurred at its margin. The relationship between the site of CNV and macular WZs suggests that macular WZs may be areas which are vulnerable to AMD and which are predisposed to CNV by the resulting hypoxia-ischaemia.