Comparison of Retinal Thickness in Diabetic Patients with Healthy Controls: A Cross-sectional Study

Introduction: Diabetes Mellitus (DM) is a metabolic disorder characterised by chronic hyperglycaemia, leading to systemic complications such as Diabetic Retinopathy (DR). The impact of DM on retinal thickness is of particular interest, as it can serve as an early indicator of DR progression. Aim: To assess variations in retinal thickness among diabetic patients without systemic involvement and also to correlate retinal thickness with the duration of diabetes and Glycated haemoglobin (HbA1c) levels. Materials and Methods: This cross-sectional study was conducted in the Department of Physiology at Geetanjali Medical College and Hospital, a tertiary care centre, from January 2023 to April 2024. A total of 120 participants were included, with 60 individuals in the diabetic group (group D) and 60 in the healthy control group (group N). Group D consisted of participants with a diabetes duration of 1.5-10 years and HbA1c levels above 6.5%, while those with systemic or ocular complications of diabetes were excluded. Retinal thickness was measured using Optical Coherence Tomography (OCT), and HbA1c levels were recorded. Statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) version 20.0, employing independent samples t-tests and correlation analysis. Results: The study included 60 participants in each group, with group N (Control) and group D (Diabetic) having a mean age of 38.67±5.38 years and 48.17±8.76 years, respectively, with the latter being significantly older. The gender distribution varied, with group N having a higher male-to-female ratio (51 males and 9 females) compared to group D (39 males and 21 females). The diabetic group exhibited significantly reduced retinal thickness compared to the controls, with mean values of 190.88±22.33 μm in the right eye and 188.02±19.58 μm in the left eye. In contrast, the control group had mean values of 206.02±21.29 μm in the right eye and 210.33±18.14 μm in the left eye (p-value<0.001). Correlation analysis showed no significant associations between HbA1c levels, duration of diabetes and retinal thickness. Conclusion: This study highlights significant reductions in retinal thickness among diabetic patients compared to healthy controls. The lack of correlation with HbA1c levels and diabetes duration suggests the need for further investigation into additional factors influencing retinal changes in DM.