Association of severity of diabetic retinopathy with corneal endothelial and thickness changes in patients with diabetes mellitus

Objective: To analyse the central corneal thickness, endothelial cell density and morphology in patients with diabetes mellitus (DM). Methods: We analysed corneal endothelium, i.e. central corneal thickness (CCT), endothelial cell density (ECD), coefficient of variation in cell size (CV), and hexagonality (Hex) with specular microscopy in patients with type 2 DM and compared with age-matched controls. The influence of diabetic retinopathy (DR) severity, duration of DM, and level of glycosylated haemoglobin (HbA1c) was also analysed. Results: The study cohort included 592 eyes of 592 diabetic patients and 596 eyes of 596 control subjects. A significant difference was found in CCT (522.1 ± 36.6 μm in DM, 514.9 ± 37.1 μm in controls; P = 0.001), ECD (2484.5 ± 299.5 cells/mm2 in DM, 2555.9 ± 258.2 cells/mm2 in controls; P = 0.017), CV (40.3 ± 6.1 in DM, 37.2 ± 6.1 in controls; P < 0.001) and Hex (39.9 ± 5.2 in DM, 44.6 ± 6.0 in controls; P < 0.001). The longer duration of DM (> 10 years) and poor glycaemic control (HbA1c > 7.5%) were associated with similar results. A significantly reduced ECD (P < 0.001) and Hex (P = 0.001) and higher CV (P = 0.007) and CCT (P = 0.01) was noted when assessed against various stages of DR. Multivariate analysis showed that increasing age was significantly associated with lower ECD (P < 0.001), Hex (P < 0.001), and CCT (P = 0.004); and a higher CV (P < 0.001). Conclusions: DM has deleterious effects on corneal endothelium and thickness. The presence of DR may further warrant a thorough corneal evaluation, especially when planning intraocular surgery.