Use of choroidal vascularity index for choroidal structural evaluation in smokers: an optical coherence tomography study

Purpose To compare the choroidal vascularity index (CVI) and choroidal thickness (CT) in smokers and healthy non-smoking subjects using spectral-domain optical coherence tomography (SD-OCT). Methods Forty-two smokers with no systemic disorders and 46 age-sex matched healthy volunteers were included in the study. SD-OCT was used to measure choroidal thickness at the fovea and 1500 mu m intervals from the foveal centre in both nasal and temporal directions. Choroidal images were binarized and segmented to the luminal area (LA), stromal area (SA), and total choroidal area (TCA) using ImageJ software. The choroidal vascularity index was calculated as the ratio of LA to TCA. Smoking subjects were divided into three groups according to pack-year exposure: 10-20 pack-years, 20-30 pack-years, and >30 pack-years. Subgroup analysis was performed to evaluate the relationship between CT/CVI/LA/SA/TCA and pack-years. Results The mean age of the smokers and non-smokers was 43.1 +/- 7.26 years and 41.82 +/- 9.92 years, respectively (p = 0.51). The mean subfoveal choroidal thickness was 301.57 +/- 55.04 mu m in smokers and 303.38 +/- 53.42 mu m in non-smokers (p = 0.826). No significant difference was observed between groups for CT values in the subfoveal location or at 1500 mu m intervals in the nasal and temporal direction from the fovea. The CVI was significantly lower in smokers (65.4 +/- 2.3%) than in non-smokers (66.3 +/- 2.5%) (p = 0.021). In the subgroup analysis, subjects with >20 pack-years of smoking had a significantly lower CVI than non-smokers, but those between 10-20 pack-years did not. A negative correlation was found between the CVI and smoking, as measured by cigarette pack-years (r = -0.226,p = 0.04). Conclusion The CVI was significantly decreased in smokers compared to healthy controls. The study results suggest that the CVI could be a non-invasive tool for evaluating choroidal vascular changes in smokers.