Comparison of the effects of chewing versus smoking tobacco on corneal endothelial health

Abstract Purpose: To evaluate the effect of chewing versus smoking tobacco on corneal endothelial health. Methods: This was a cross-sectional, observational study analyzing 1797 eyes of 1797 patients. The study cohorts comprised tobacco smokers (N=605); tobacco chewers (N=595), and non-tobacco users (N=597). All the subjects underwent corneal endothelial evaluation by non-contact specular microscopy (EM 4000 Tomey Nishi-Ku, Nagoya, Aichi, Japan). Endothelial cell density (ECD; cells/mm 2 ), coefficient of variation in cell size (CV; %), hexagonality (Hex; %), and central corneal thickness (CCT; µm) were recorded and compared among the 3 groups. Results: ECD (p<0.001) was significantly lower in chewers when compared to smokers, and was significantly highest in non-tobacco users, whereas CV (p<0.001) and CCT (p=0.009) were found to be significantly higher in chewers when compared to smokers and non-tobacco users. Hex (p<0.001) was significantly lower in chewers when compared with non-tobacco users and smokers. Multivariate linear regression analysis showed that increasing age was a significantly important factor in both the smokers and chewers in all the study parameters (negatively for ECD, Hex, and CCT; and positively for CV), except for CCT in chewers. Frequency and duration of smoking were significantly associated with higher CCT in smokers as well as chewers, whereas the duration of tobacco chewing negatively impacted ECD and Hex in chewers additionally. Conclusions: Chewing tobacco, especially long-term, appears to be detrimental to the corneal endothelial structure when compared to smoking.