Evaluation of Retinal Nerve Fiber Layer Thickness Using Optical Coherence Tomography in Patients with Diabetes Mellitus and Its Association with Severity of Diabetic Retinopathy

Abstract

Background: Diabetes mellitus is a chronic metabolic disorder associated with progressive retinal neurovascular damage. Retinal neurodegeneration is now recognized as an early component of diabetic ocular disease alongside microvascular changes.
Aim: To evaluate retinal nerve fiber layer (RNFL) thickness using optical coherence tomography (OCT) in diabetic patients and assess its association with severity of diabetic retinopathy (DR).
Materials and Methods: This hospital-based cross-sectional study was conducted at Darbhanga Medical College and Hospital, Bihar, from July 2024 to June 2025. A total of 100 diabetic patients underwent comprehensive ophthalmic evaluation and OCT-based RNFL measurement. DR severity was graded using ETDRS classification.
Results: Mean RNFL thickness showed a progressive decline with increasing DR severity (p < 0.001). Significant negative correlation was observed between RNFL thickness, duration of diabetes, and HbA1c levels.
Conclusion: RNFL thinning correlates strongly with severity of diabetic retinopathy and may serve as an early neurodegenerative biomarker.