Correlation of Central Corneal Thickness, Central Macular Thickness, and Corneal Endothelial Cell Parameters with Severity of Diabetic Retinopathy and HbA1c Levels in Type 2 Diabetes Mellitus

Abstract

Purpose: The aim of this study is to evaluate the association of central corneal thickness (CCT), corneal endothelial cell parameters, and central macular thickness (CMT) with the severity of diabetic retinopathy (DR) and glycaemic control in patients with type 2 diabetes mellitus (T2DM).
Methodology: This cross-sectional observational study was conducted over 12 months at a tertiary care centre and included 100 patients with T2DM. All participants underwent comprehensive ophthalmic evaluation, including fundus examination for grading of DR, specular microscopy for endothelial cell density (ECD), coefficient of variation (CV), and hexagonality, pachymetry for CCT, and optical coherence tomography for CMT. Glycaemic control was assessed using HbA1c levels. Associations between ocular parameters, DR severity, and HbA1c were analyzed using appropriate statistical tests.
Results: Of the 100 patients studied, 29% had diabetic retinopathy. A statistically significant inverse relationship was observed between ECD and increasing severity of DR (p < 0.001). Progressive worsening of DR was associated with a significant increase in CV and a reduction in hexagonality (p < 0.05). Central corneal thickness increased significantly with advancing DR severity (p = 0.012). Central macular thickness showed a progressive and significant increase from patients without DR to those with proliferative DR (p < 0.001). Patients with poor glycaemic control (HbA1c > 7.5%) demonstrated significantly lower ECD, higher CV, reduced hexagonality, increased CCT, and increased CMT.
Conclusion: Corneal endothelial alterations, increased central corneal thickness, and macular thickening correlate significantly with the severity of diabetic retinopathy and poor glycaemic control. Comprehensive assessment of both anterior and posterior segment parameters may aid in early detection of ocular involvement and improve clinical management of patients with type 2 diabetes mellitus.