Effects of cigarette smoking on retinal thickness and choroidal vascularity index: a systematic review and meta-analysis
Bibliographic record
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 < 0.00001), indicating compromised choroidal vascularity. In contrast, the impact of smoking on subfoveal choroidal thickness (SFCT) was not statistically significant (mean difference: 3.88 μm, 95% CI: -7.34 to 15.10, p = 0.50), with high heterogeneity (I² = 79%). Additionally, the full-retinal thickness (FRT) did not show a significant difference between smokers and nonsmokers. CONCLUSION: Cigarette smoking negatively affects choroidal vascularity, as indicated by a significant reduction in CVI. However, its impact on FRT and SFCT remains unclear and requires further research. These findings highlight the importance of smoking cessation for eye health and suggest that CVI is a valuable noninvasive biomarker for monitoring vascular changes in smokers. TRIAL REGISTRATION: PROSPERO registration number: CRD42024627478.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.008 | 0.024 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.016 | 0.029 |
| Bibliometrics | 0.006 | 0.007 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".