Choroidal Watershed Zone and Growth of Polypoidal Choroidal Vasculopathy

Abstract

ABSTRACTPurpose: To investigate the topographic relationship between polypoidal choroidal vasculopathy (PCV) growth and choroidal watershed zones (CWZ) by using indocyanine green angiography (ICGA).Materials and Methods: We evaluated PCV lesions smaller than the CWZ at baseline and followed up more than 6 months. The CWZ was traced in the early phase ICGA at baseline. The vascular lesion of PCV was traced in baseline and follow-up ICGA. These traces were overlapped and topographic relationships between CWZs and PCV growth were evaluated.Results: Among 31 eyes of 31 patients, enlargement of a PCV lesion was observed in 20 patients (64.5%) at mean follow-up of 30.4 months (6–68 months). A topographical relationship between the CWZ and PCV growth was demonstrated in 14 eyes (70.0%), as the shape of the PCV lesion conformed to the boundary of the CWZ, and/or the growth of the branching vascular network was aligned to the direction of the CWZ extension to the periphery. Growth beyond the boundary of the CWZ was noted in 9 eyes (45.0%), however growth area was greater inside the CWZ than outside in all eyes. Of 15 eyes of extrafoveal lesion at baseline, 8 eyes in which the vascular lesion progressed to the fovea had the CWZ involving the fovea, whereas PCV in three eyes with an extrafoveal CWZ remained as a non-subfoveal disease after mean follow-up of 17.0 months (p = 0.019).Conclusions: A subfoveal CWZ was related to PCV growth to the fovea. Topographical relationships between PCV growth and the CWZ suggest that choroidal circulation is a predisposition for PCV growth.