Pathologic study of early manifestations of polypoidal choroidal vasculopathy and pathogenesis of choroidal neo-vascularization.

Polypoidal Choroidal Vasculopathy is a disease of the dilated and multi-layered choroidal venules. Occlusion of these choroidal vascular channels might give rise to choroidal stasis and ischemia leading to serous RPE detachment and a sub-RPE neovascular membrane. Gross dilatation of the choroidal venules and capillaries in the sub-RPE neovascular membrane leads to the characteristic "grape like" structures, a unique clinical feature in this disease entity. These pathologic features of PCV are different from the pathologic changes of neovascular age-related macular degeneration (nAMD). Consequently, PCV and nAMD are two distinct diseases. However, in the late stage of both entities, choroidal ischemia in both diseases, lead to sub-RPE neovascularization and subsequent sub-RPE and/or sub-retinal hemorrhage. These results in both entities showed comparable clinical and pathologic features that are frequently mistaken PCV as a sub-type of Neovascular AMD.