Effects of cigarette smoking on retinal thickness and choroidal vascularity index: a systematic review and meta-analysis

Abstract Background Smoking increases oxidative stress, affecting the vascular endothelium by decreasing the antioxidant vitamin C and disrupting regular nitric oxide activity. It reduces blood flow in the retina and choroid due to increased vascular resistance and compromised choroidal blood flow regulation compared to nonsmokers. This systematic review and meta-analysis aimed to elucidate the impact of cigarette smoking on retinal thickness and the choroidal vascularity index (CVI). Methods A comprehensive literature search was performed across multiple databases, including Web of Science, Medline, PubMed, and Embase, adhering to the PRISMA and MOOSE guidelines. Observational studies were selected to explore the relationships between smoking and ocular parameters such as CVI, full-retinal, and choroidal thickness. Two independent reviewers conducted the data extraction and quality assessment using a modified Newcastle–Ottawa scale. Statistical analysis was performed using a random-effects model. Results Four out of the 743 identified articles, involving 702 eyes, met the inclusion criteria. The analysis revealed a significant reduction in the CVI among smokers (SMD: -0.61, 95% CI: -0.78 to -0.43, p