Impact of smoking on the ocular surface and tear film: A systematic review

The purpose of this systematic review and meta-analysis was to assess the influence of active smoking, secondhand smoke, and the use of electronic cigarettes (e-cigarettes) on tear film stability and the health of the ocular surface with a goal of determining their role in Dry Eye Disease (DED). A thorough literature search was conducted in prominent databases to yield clinical studies that have documented tear film parameters (Tear Break-Up Time, Schirmer test, tear osmolarity) and ocular surface changes in smokers, individuals exposed to secondhand smoke, and electronic cigarette users. Pooled using random-effects meta-analysis, eligible studies were identified, and heterogeneity was analyzed using the I² statistic. The aggregated data revealed that active and passive smokers exhibited significantly lower TBUT (SMD = −2.87) and Schirmer values (SMD = −2.79) and higher tear osmolarity (SMD = +12.55), reflective of severe tear film instability. Structural changes, such as greater central corneal staining, central corneal thinning, and lower corneal sensitivity, were also commonly observed. Similar but inhomogeneous patterns of ocular surface damage were found in e-cigarette users. Comparisons were made with other studies, such as those of Putri (2024), Harjanti and Indrawati (2024), Miglio et al. (2021), Dabas et al. (2025), and Zaib et al. (2023)—broadly consistent with these results, although variations in methodology and groups were responsible for some variation. Tobacco exposure, in the form of conventional smoking, secondhand smoke, or e- cigarette use, has been linked to severe tear film dysfunction and ocular surface injury. These observations underscore the importance of early ophthalmic examination and smoking cessation counseling, particularly in high-risk individuals.