Evaluating retinal and choroidal vascularity changes in active and passive smokers over 50 years old : a population-based study in Hong Kong

Abstract

Smoking is a modifiable risk factor for some common retinal diseases such as age- related macular degeneration, central serous chorioretinopathy, and diabetic retinopathy. Optical coherence tomography angiography (OCTA) and optical coherence tomography (OCT) are non-invasive and efficient techniques for assessing the blood supply of the retina, which includes the retinal and choroidal vasculatures. Evaluating the effect of smoking on the retinal and choroidal vasculatures in active and passive smokers with no apparent ocular disease by utilizing quantifiable OCTA and OCT parameters may help identify features of early toxicity from smoking. There are currently few reports on this topic in the Chinese population, and the previous studies in other populations showed conflicting results and/or lacked analysis of passive smokers. Our study aims to: 1) compare the retinal vasculature, choroidal vasculature, and best corrected visual acuity (BCVA) between Chinese smokers and non-smokers ≥50 years of age in Hong Kong; 2) identify any influence factors of the novel parameter, choroidal vascularity index (CVI); and 3) to obtain normal reference values of CVI for this population. We recruited 1840 participants, including 1233 non-smokers, 235 active smokers, and 372 passive smokers, with no history of ocular disease besides mild cataract or previous cataract surgery. All participants underwent a comprehensive ophthalmological examination. Central macular thickness (CMT) and retinal vasculature parameters including avascular fovea zone (FAZ), vessel density (VD), and perfusion (PD) were assessed automatically by the OCTA inbuilt AngioPlex device. Subfoveal choroidal thickness (SFCT) and CVI were measured automatically from OCT images using custom software. No significant difference with non-smokers was observed in active smokers for retinal/choroidal parameters, while passive smokers had significantly higher VD and PD, lower CVI, and worse BCVA, after adjusting for potential confounders. The decreased CVI was correlated with increasing exposure to second-hand smoke. Apart from passive smoking, increasing age, female gender, longer axial length, lower spherical equivalent, and thinner SFCT were also associated with lower CVI. The presence of these findings in our passive smokers lend support that second- hand smoke may potentially increase the risk of chorioretinopathy development, and the potential role of using CVI to monitor for early indication of asymptomatic disease.