Pachychoroid neovasculopathy: a type-1 choroidal neovascularization belonging to the pachychoroid spectrum-pathogenesis, imaging and available treatment options.

Abstract

The purpose of this paper is to provide a meaningful literature review about the epidemiology, pathogenesis, imaging and treatment of pachychoroid neovasculopathy (PNV). A computerized search from inception up to December 2019 of the online electronic database PubMed was performed using the following search string: "pachychoroid neovasculopathy". The reference list in each article was scanned for additional relevant publications. PNV is a type-1 choroidal neovascularization, overlying focal areas of choroidal thickening and dilated choroidal vessels. It can develop in patients affected by pachychoroid pigment epitheliopathy or chronic central serous chorioretinopathy. The absence of drusen, the presence of pachydrusen, younger age of onset and choroidal thickening distinguish it from neovascular age-related macular degeneration (AMD). PNV incidence and prevalence data are lacking. Its pathophysiology is not fully understood, but angiogenic mechanisms involved in neovascular AMD may be different from those in PNV. Due to optical coherence tomography (OCT) improvements, PNV can be diagnosed more easily than before. In particular, PNV shows a shallow pigment epithelium detachment with an undulating retinal pigment epithelium over a subfoveal choroidal thickening, associated with vein enlargement in Haller's layer (named pachyvessels) and choriocapillaris thinning. On OCT angiography, PNV reveals tangled hyper-reflective filamentous neovessels in the choriocapillaris itself. The current first-line PNV treatment is intravitreal anti-VEGF (vascular endothelial growth factor) injections with a treat-and-extend regimen. In particular, aflibercept shows a higher rate of fluid absorption than others. In the case of fluid recurrence or persistence, photodynamic therapy is a valid alternative. Ongoing research into pathophysiology and imaging improvements may be helpful in defining prognostic criteria and stratifying patient risk, allowing responsible monitoring and management of PNV.