The Effect of Diabetes Mellitus on Corneal Endothelial Cells and Central Corneal Thickness: A Case-Control Study

Purpose: The aim of this study was to evaluate the characteristics of corneal endothelial cells and central corneal thickness (CCT) in patients with diabetes mellitus (DM), comparing them with those of healthy subjects (controls) and to determine potential factors affecting the corneal parameters in patients with DM. Methods: Participants in this study were 72 patients with DM and 88 healthy controls. Diabetic patients were further classified into groups depending on the severity of diabetic retinopathy (no retinopathy, mild, moderate, severe non-proliferative diabetic retinopathy, and proliferative diabetic retinopathy). All participants underwent non-contact specular microscopy to evaluate corneal endothelium parameters and CCT, while factors affecting endothelial cell density and CCT in patients with DM were also analyzed. Results: Patients with DM presented significantly decreased endothelial cell density compared to controls (2,297.9 ± 311.3 and 2,518.3 ± 243.7 cells/mm2, respectively; p < 0.001), while the two groups did not differ significantly in any other measured corneal parameter. In the diabetic group, the multivariate analysis showed a significant association between decreased endothelial cell density and increased HbA1c (p < 0.001), longer DM duration (p = 0.003), and more severe diabetic retinopathy status (p = 0.008). Conclusion: DM seems to affect the corneal endothelium, since endothelial cell density was decreased in the diabetic group, while duration of disease, HbA1c levels, and severity of retinopathy were significantly associated with changes in endothelial cell density and should be taken into account.