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

Purpose: To describe the histopathologic features of an early case of presumably bilateral polypoidal choroidal vasculopathy (PCV) in two eyes obtained at autopsy from a patient with no prior ocular therapy.

Observations: The choroid of both eyes at the macular and peripapillary regions was greatly thickened with dilated, thin walled choroidal venules intertwining with arteriosclerotic arterioles in the Sattler's layer of the choroidal vasculature. At the temporal and nasal equatorial regions of both eyes many of these congested venular channels abruptly disappeared and were replaced by loose connective tissue with loss of the normal choroidal stromal tissue and uveal melanocytes. A few remaining venules showed intraluminal sloughing of endothelial cells and deposition of fibrinous material networks suggesting occlusion of these choroidal venules. At this equatorial location, serous detachment of retinal pigment epithelium (RPE) appeared and a thin neovascular membrane with cords of endothelial cell invaded into the sub-RPE space. Anteriorly, the neovascular membrane expanded and bulged into the sub-retinal space with dilated neovascular capillaries in a "grape like" or polypoidal configuration.

Conclusion and importance: 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.