Influence of scanning area on choroidal vascularity index measurement using optical coherence tomography

PURPOSE: Recently, choroidal vascularity index (CVI) is proposed as a novel tool to evaluate the choroidal vasculature. In this study, we investigate the impact of scanning area on CVI measurement using spectral-domain optical coherence tomography (SD-OCT). METHODS: Spectral-domain optical coherence tomography (SD-OCT) using enhanced depth imaging mode was performed in 30 eyes from 15 normal subjects. Three scanning areas were compared: dingle foveal scan; central macular scans scan passing through central 1000 microns circle on Early Treatment Diabetic Retinopathy Study (ETDRS) grid, inner circle; and total macular cube scans. Binarization of OCT B-scans and segmentation of the binarized choroid layer were achieved using a previously reported validated automated software. Choroidal vascularity index (CVI) percentage was calculated. Degree of agreement among foveal, central macular and total macular CVI was assessed using intraclass correlation coefficient (ICC) and was plotted using Bland-Altman plot. RESULTS: The mean CVI in subfoveal, central macular and total macular scans was 49.95 ± 4.84%, 50.00 ± 4.68% and 51.10 ± 4.63%, respectively. Intraclass correlation coefficient (ICC) was more than 0.8 for all three comparisons subfoveal versus central macular CVI, ICC = 0.92 (95% CI: 0.84-0.96); central macular versus total macular CVI, ICC = 0.90 (95% CI: 0.82-0.96); subfoveal versus total macular CVI, ICC = 0.92 (95% CI: 0.85-0.95). No significant differences in variance (all p > 0.05) were noted among CVI measured from the three scanning areas. CONCLUSION: Choroidal vascularity index (CVI) measurements were highly reproducible using subfoveal, central and total macular scans in healthy individuals. Single foveal scan choroidal vascularity represents total macular choroidal vascularity in healthy population.