Choroidal vascularity index as a measure of vascular status of the choroid: Measurements in healthy eyes from a population-based study

Abstract

The vascularity of the choroid has been implicated in the pathogenesis of various eye diseases. To date, no established quantifiable parameters to estimate vascular status of the choroid exists. Choroidal vascularity index (CVI) may potentially be used to assess vascular status of the choroid. We aimed to establish normative database for CVI and identify factors associated with CVI in healthy eyes. In this population-based study on 345 healthy eyes, choroidal enhanced depth imaging optical coherence tomography scans were segmented by modified image binarization technique. Total subfoveal choroidal area (TCA) was segmented into luminal (LA) and stromal (SA) area. CVI was calculated as the proportion of LA to TCA. Linear regression was used to identify ocular and systemic factors associated with CVI and subfoveal choroidal thickness (SFCT). Subfoveal CVI ranged from 60.07 to 71.27% with a mean value of 65.61 ± 2.33%. CVI was less variable than SFCT (coefficient of variation for CVI was 3.55 vs 40.30 for SFCT). Higher CVI was associated with thicker SFCT, but not associated with most physiological variables. CVI was elucidated as a significant determinant of SFCT. While SFCT was affected by many factors, CVI remained unaffected suggesting CVI to be a more robust marker of choroidal diseases.

Comparison of Choroidal Vascularity Markers on Optical Coherence Tomography Using Two-Image Binarization Techniques

“…39,40 In their previous publications, authors of both techniques have compared binarized images to the original OCT images and showed that dark area corresponded to lumens of choroidal vessels. 18,19 Both authors have also demonstrated high intragrader and intergrader reliability of their measurements in previous reports. 18,19 Discrepancy in CVI and L/C ratio could be explained by the differences in methodology.…”

“…All statistical analyses were performed using statistical software (SPSS version 20.0; IBM Corp. Armonk, NY, USA) and statistical significance was evaluated at 5% level. 19 (C, F, I) OCT images after binarization using technique proposed by Sonoda et al 18 (A-C) One subject in which choroidal vascularity index (CVI) is similar to luminal/ choroidal ratio (L/C ratio). (D-F) One subject in which CVI is smaller than L/C ratio.…”

“…Binarization was performed separately using techniques proposed by Sonoda et al 18 and Agrawal et al 19 Detailed algorithms for both techniques were described previously. Both techniques were carried out with ImageJ (version 1.47; provided in the public domain by the National Institutes of Health, Bethesda, MD, USA; https://imagej.nih.…”

“…18,19 This has led to the creation of a novel structural marker for choroidal vascularity, which is the ratio of vascular (or luminal) area to total choroidal area. It was termed ''choroidal vascularity index (CVI)'' by Agrawal et al 19 or ''luminal/choroidal area ratio (L/C ratio)'' by Sonoda et al 18 This new marker of choroidal vascularity has been investigated in normal physiologic conditions 18,[20][21][22][23] and also validated as a useful tool in various ocular diseases. 19,[24][25][26][27][28][29][30][31][32][33][34][35][36] Differences exist in the image binarization algorithms for the calculation of CVI and L/C ratio.…”

“…In the technique proposed by Agrawal et al, 19 a few modifications were made. The OCT scan was directly converted to 8-bit images using ImageJ default setting.…”