Distinguish polypoidal choroidal vasculopathy through choroidal alterations: A systematic review, meta‐analysis and narrative synthesis

PURPOSE: Polypoidal choroidal vasculopathy (PCV) is a vision-threatening choroidal vascular abnormality historically categorized as a subtype of neovascular age-related macular degeneration (nAMD). Accumulating evidence suggests that PCV may instead belong to the pachychoroid spectrum diseases, although its choroidal characteristics remain incompletely characterized and inconsistently reported. METHODS: PubMed, Embase and Ovid were searched for studies comparing choroidal structural and vascular parameters of PCV with healthy controls (HC), fellow eyes, nAMD or pachychoroid spectrum diseases. Outcomes supported by three or more studies were synthesized using quantitative meta-analysis, whereas outcomes supported by fewer than three studies were summarized using narrative synthesis and exploratory meta-analysis. RESULTS: Forty studies were included in the final analysis. Meta-analysis revealed that subfoveal choroidal thickness (SFCT) was significantly greater in PCV eyes than in HC, nAMD, and fellow eyes, but lower than central serous chorioretinopathy and pachychoroid neovasculopathy (PNV) eyes (all p < 0.05). PCV eyes also had lower choroidal vascularity index within the standard subfoveal width of 1.5 mm and higher choroidal vascular density (CVD) within the r = 10 mm FOV than HC eyes (p < 0.05). Narrative synthesis and exploratory meta-analysis suggested that PCV eyes may have greater total choroidal thickness than HC and nAMD eyes, as well as a higher ratio of Haller layer thickness to SFCT and larger choroidal luminal area than nAMD eyes at specific locations or areas. Besides, thick-choroid PCV demonstrated higher CVD in 200° ultra-wide ICGA images than nAMD, while the thin-choroid subtype exhibited lower CVD than PNV. CONCLUSIONS: PCV is characterized by a thicker and more vascular choroid than nAMD and HC, but a thinner and less vascular choroid than CSC and PNV. These findings, supported by both primary and exploratory meta-analyses, provide insights into PCV pathogenesis and its distinction from nAMD and other pachychoroid spectrum disorders.