Clinical implications of choroidal vascular brightness using ultra-widefield indocyanine green angiography in polypoidal choroidal vasculopathy

Polypoidal choroidal vasculopathy (PCV) is characterized by choroidal vascular abnormalities including polypoidal lesion and branching vascular networks. Not only choroidal structural changes, but also choroidal hyperpermeability and congestion are also thought to be involved in pathogenesis of PCV. We investigated choroidal vascular brightness intensity (CVB) using ultra-widefield indocyanine green angiography (UWF-ICGA) images and analyzed its association with clinical features in patients with PCV. In this study, 33 eyes with PCV and 27 eyes of age-matched controls were included. CVB was measured by extracting the enhanced pixels of choroidal vessels after the reference brightness across the images was adjusted to be uniform. Associations between choroidal vascular features and the clinical features of PCV were also determined. The mean CVB was higher in PCV than control eyes, regardless of the segmented region (all p < 0.001). CVB was also higher at the posterior pole than at the periphery, and the inferior quadrants were brighter than the superior quadrants in both the PCV and control group (all p < 0.05). In affected eyes, CVB was higher than in unaffected fellow eyes at the posterior pole, whereas there was no difference at the periphery. Posterior pole CVB correlated significantly with subfoveal choroidal thickness (r = 0.502, p = 0.005), polyp number (r = 0.366 p = 0.030), and the greatest linear dimension (r = 0.680, p = 0.040). Greatest linear dimension was positively correlated with CVB at posterior pole (p = 0.040), whereas SFCT or CVD in all regions didn't show the significant correlation. The UWF ICGA results showed an increase in CVB at the inferior quadrants and posterior pole, suggesting venous outflow congestion in PCV eyes. CVB might provide more substantial information on the phenotype than other choroidal vascular features.