Choroidal Watershed Zone and Growth of Polypoidal Choroidal Vasculopathy

To investigate the topographic relationship between polypoidal choroidal vasculopathy (PCV) growth and choroidal watershed zones (CWZ) by using indocyanine green angiography (ICGA).

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.

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).

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.