Choroidal vascularity index is independent of ocular and image-based factors in healthy eyes: a systematic review and meta-analysis

Choroidal vascularity index (CVI) has been extensively used to assess choroidal health in posterior eye disease; however, interpretation is hindered by conflicting evidence on effect of normal physiological factors on CVI. Thus, this review aimed to derive a normative value for CVI and understand its relationship with various normal ocular/image-based factors. Studies were screened for eligibility, defined as eyes with normal ocular parameters (refractive error (RxE) < ± 6 DS, intraocular pressure (IOP < 21 mmHg) and no posterior segment disease and 98 studies were included. Pooled weighted average of subfoveal CVI extracted from healthy eyes (n = 5332 eyes) was 66.50% [CI 65.67–67.32]. Secondary stratifications (time of scan, device wavelength, imaging mode, region of interest, systemic factors) and meta regression (age, RxE and IOP) were insignificant on CVI (p = 0.579–0.872), however Best corrected visual acuity showed positive correlation (p = 0.037). Unaltered, narrow confidence interval in sensitivity analysis, complemented by non-significant publication bias indicated robustness of the synthesised data. These results provide the highest-level evidence in hierarchy of the first normative subfoveal CVI value synthesised from literature and that it is not influenced by most person, eye and imaging factors in healthy eyes.