Choroidal vascularity index – a novel optical coherence tomography parameter for disease monitoring in diabetes mellitus?

Purpose To propose the use of choroidal vascularity index ( CVI ) as a novel tool to assess vascular status of the choroid using image binarization of enhanced depth imaging ( EDI ) optical coherence tomography ( OCT ) scans in diabetes mellitus ( DM ). Methods A prospective cross‐sectional study was performed at a tertiary referral eye care centre in Singapore. Age and gender matched EDI ‐ OCT scans of 38 eyes of 19 patients with DM were compared with eyes of healthy controls ( n  = 19). The choroidal images were binarized into luminal areas ( LA ) and stromal areas ( SA ). Choroidal vascularity index (CVI) was defined as the proportion of LA to total circumscribed subfoveal choroid area ( TCA ). Mean choroidal thickness, mean retinal thickness and mean CVI between patients and controls were compared using student's t‐test. Results There were no significant differences in TCA (p = 0.78), LA (p = 0.90), SA (p = 0.33), average choroidal (p = 0.40) or retinal thickness (p = 0.70) between patients with DM and controls. However, there was a significantly lower CVI in patients with DM as compared to controls (65.10 ± 0.20 versus 67.20 ± 0.16, p < 0.0001). Conclusion Eyes of patients with DM showed decreased CVI with no corresponding change in choroidal thickness. Image binarization may be potentially useful as a tool to assess choroidal structures and vasculature.