Analysis of choroidal morphology and comparison of imaging findings of subtypes of polypoidal choroidal vasculopathy: a new classification system

Abstract

AIM: To classify polypoidal choroidal vasculopathy (PCV) into 2 subtypes based on the subfoveal choroidal thickness (SFCT) and to further evaluate their multimodal image features. METHODS: A retrospective observational case series study. Sixty-four eyes of 64 patients with PCV were enrolled and classified into 2 groups based on SFCT (thick-choroid group/thin-choroid group). Then further analyze the spectrum domain optical coherence tomography (SD-OCT) and indocyanine green angiography (ICGA) differences of the two subtypes. Imaging analysis included measurement of SFCT, maximum vascular diameter ratio (MVDR), choroidal vascularity index (CVI), central macular thickness (CMT), and the presence of pigment epithelial detachment (PED) on SD-OCT. Polypoidal lesions (polyps) number, branching vascular network (BVN) area, greatest linear dimension (GLD), and the choroidal vascular hyperpermeability (CVH) were analyzed by ICGA. RESULTS: The distribution of SFCT was bimodal with two peaks at 195 and 285 μm, and a trough at 225 μm. The 225 μm was taken as the cutoff point for the following classification of thick/thin choroid groups. The PCV eyes in the thick-choroid group presented with greater MVDR, CVI within 3 and 6 mm of the fovea, but lower CMT, less PED, small PED diameters on SD-OCT scans, and fewer polyps, smaller BVN and GLD, but more frequency of CVH on ICGA. CONCLUSION: The SFCT at 225 μm can be used as a readily available indicator for the classification of PCV subtypes. The thick-choroid group presents much apparent enlargement of the choroidal layer and vasculature expansion, which indicates different pathogenesis of the two subtypes.

Keywords

• polypoidal choroidal vasculopathy
• spectral-domain optical coherence tomography
• indocyanine green angiography
• subfoveal choroidal thickness