Peripapillary Retinal Nerve Fiber Layer Changes in Patients with Diabetes Mellitus: A Case-control Study

Purpose To evaluate peripapillary retinal nerve fiber layer (RNFL) changes in patients with diabetes mellitus (DM) and compare them with those of normal population. In addition, this study aims to determine potential factors, affecting RNFL changes in patients with DM. Methods Participants in this study were 107 patients (211 eyes) with DM and 100 healthy controls (200 eyes). Diabetic patients were further classified into four groups depending on severity of diabetic retinopathy (no retinopathy, mild, moderate, severe nonproliferative diabetic retinopathy, and proliferative diabetic retinopathy, while presence of macular edema was also assessed. All participants underwent spectral-domain optical coherence tomography (SD-OCT) to measure RNFL thickness, while demographic and clinical characteristics of the participants were also recorded. Results Patients with DM with or without DR presented significantly decreased peripapillary RNFL thickness in all quadrants. In the diabetic group, the multivariate analysis showed a significant association between decreased average RNFL thickness and increased HbA1c (p< 0.001), longer DM duration (p= 0.007), and more severe diabetic retinopathy status (p= 0.016), while presence of DME, age, gender, hypertension, and hyperlipidemia were not found to be associated with RNFL thickness decrease. Conclusion Diabetes mellitus seems to affect RNFL thickness, suggesting that early neurodegenerative changes may occur, potentially before microvascular alterations. Since duration of disease, DR severity, and HbA1c levels were associated with RNFL thinning, modifying glycemic control seems to be important to potentially prevent the development of DM complications.