RETINAL NERVE FIBER LAYER THICKNESS IN DIABETIC PATIENTS WITH AND WITHOUT DIABETIC RETINOPATHY USING SPECTRAL-DOMAIN OPTICAL COHERENCE TOMOGRAPHY

Abstract

Background: Diabetes mellitus is associated with retinal neurodegenerative changes that may occur before clinically detectable diabetic retinopathy. Spectral-domain optical coherence tomography (SD-OCT) permits quantitative assessment of retinal nerve fiber layer (RNFL) thickness and may help identify early neuroretinal structural changes. Methods: A hospital-based comparative study was conducted from September 2024 to September 2025 among 75 participants, with 25 participants in each group. All participants underwent comprehensive ophthalmic examination and SD-OCT assessment of average and quadrant-wise RNFL thickness. Clinical and systemic parameters including diabetes duration and HbA1c were recorded. Data were analysed using SPSS version 26. Continuous variables were compared using appropriate parametric tests, categorical variables using chi-square test, and Pearson correlation was used to assess relationships between RNFL thickness and systemic factors. A p-value <0.05 was considered statistically significant. Results: Mean average RNFL thickness was 100.3 ± 4.9 µm in controls, 95.1 ± 5.1 µm in diabetes without retinopathy, and 86.7 ± 4.7 µm in NPDR (p<0.001). All four quadrants showed significant progressive thinning, with the greatest reduction between controls and NPDR occurring in the inferior quadrant (16.8 µm). RNFL thickness demonstrated significant inverse correlations with diabetes duration (r=−0.46, p<0.001) and HbA1c (r=−0.42, p<0.001). Conclusion: RNFL thickness progressively decreased from healthy controls to diabetes without retinopathy and NPDR. SD-OCT may therefore provide a useful quantitative marker of diabetic neuroretinal structural involvement.