Cumulative Effects of Smoking and Diabetes Mellitus on Corneal Endothelial Cell Parameters

To compare the corneal endothelial morphometric properties and central corneal thickness (CCT) values in patients with diabetes mellitus (DM) and age-matched healthy subjects and to determine whether smoking increases the effects of DM on these corneal parameters.

This prospective study included patients with type 2 DM and their age-matched controls. The smoking history of all participants was evaluated. Corneal endothelial cell properties including endothelial cell density (ECD), average cell area (AVG), coefficient of variation of cell area (CV), and percentage of hexagonal cells (HEX) were obtained using a noncontact specular microscope. Consequently, CCT was measured using an ultrasound pachymeter.

This research analyzed 153 subjects in the DM group and 146 subjects in the control group. There were no statistically significant differences in the age, sex, and smoking status of the participants in 2 groups (P > 0.05). The corneal endothelial cell measurements including ECD, AVG, CV, and HEX did not show any statistically significant differences between these groups (P > 0.05). However, CCT of patients with DM was statistically significantly thicker than that of the controls (P = 0.005). The ECD values of the smokers with DM (2435 ± 325 cells/mm) were statistically significantly lower than those of nonsmoker healthy subjects (2559 ± 279 cells/mm P = 0.008). However, the AVG, CV, HEX, and CCT values of the smokers with DM were not statistically significantly different compared with nonsmoker healthy subjects (P > 0.05).

Although neither only DM nor only smoking has a statistically significant effect on corneal endothelial morphometric properties, coexistence of DM and smoking causes a significant decrease in ECD.