Although researchers have long known diabetes can increase a patient’s risk of corneal complications such as endothelial damage, recurrent erosions, persistent epithelial defects, reduced sensitivity and superficial keratitis, less is known about the interplay between diabetes and other risk factors, such as smoking.

Researchers from Turkey studied 299 eyes of 299 patients—153 with diabetes and 146 healthy controls—to clarify the effects of smoking on the cornea in patients who also have diabetes. They found that neither diabetes nor smoking has a significant effect on the corneal endothelium; however, when the two were present in the same patient, endothelial cell density was significantly lower than nonsmoking healthy controls (2,435±325cells/mm² vs. 2,559±279cells/mm²).

They also measured average cell area, the extent of variation in cell area, percentage of hexagonal cells precent and central corneal thickness to get a complete picture of the corneal endothelial morphometric properties. While diabetes patients had statistically significantly thicker corneas than those of controls, there were no significant differences found in the other metrics.

Further research is necessary to better understand the cumulative effects of smoking and diabetes on the corneal endothelium, but the current data suggests additional preventions might be considered to avoid endothelial decompensation during ocular surgeries on patients with DM who also smoke, the study concludes.