Does Well-Controlled Type 2 Diabetes Mellitus Affect Corneal Endothelium? A Comparative Study

Background/Objectives: The aim of this study is to compare the parameters of the corneal endothelium in a group of patients with well-controlled type 2 diabetes (study group) to those of patients who do not have type 2 diabetes (control group). Methods: The study aims to compare the corneal endothelium parameters of 80 eyes (80 patients) with well-controlled type 2 diabetes to 80 eyes (80 patients) without type 2 diabetes. The endothelial cell density (ECD), percentage of hexagonal cells (%HEX), coefficient of variation in cell size (CV), and central corneal thickness (CCT) were recorded using a non-contact specular microscope (Nidek CEM-530, Nidek Co., Ltd., Gamagori, Japan). Best-corrected visual acuity (BCVA) and intraocular pressure (IOP) were also measured. Results: The groups were matched for age and sex. A significantly lower ECD value was observed in the group of patients with type 2 diabetes (2480.76 cells/mm² ± 303.48) compared to the control group (2629.64 cells/mm² ± 304.73) (p = 0.002). BCVA was also significantly lower in the study group (0.44 ± 0.18) compared to the control group (0.50 ± 0.19) (p = 0.049). No statistically significant differences were found between the groups in terms of IOP, CV, %HEX, and CCT. Conclusions: Patients with well-controlled type 2 diabetes exhibit a lower ECD compared to individuals without diabetes, even in the absence of advanced diabetic complications. These subtle changes may have clinical implications for preoperative evaluation and long-term management in diabetic patients. The other morphological parameters of the corneal endothelium remain comparable between the groups.