Normative Profile of Retinal Nerve Fiber Layer Thickness using Spectral Domain Optical Coherence Tomography in Healthy Omani Adults: a cross-sectional study

Background Optical coherence tomography (OCT) is essential for diagnosing glaucomatous and neurodegenerative optic neuropathies. However, diagnostic accuracy relies on population-specific normative databases to avoid misinterpretation. As no large-scale reference data exist for the Omani population, this study aimed to establish normative peripapillary retinal nerve fiber layer (pRNFL) thickness values and evaluate the influence of demographic and anatomical factors in healthy Omani adults. Methods In this hospital-based cross-sectional study, 378 healthy Omani adults (756 eyes) aged 18 years were recruited. Inclusion criteria required intraocular pressure 21 mmHg, refractive error within 1.0 D, and no ocular or systemic comorbidities. pRNFL thickness and optic nerve head (ONH) parameters were measured using Spectral Domain-OCT (Cirrus HD-OCT 5000) by a single trained technician to ensure data quality. Statistical analysis included independent samples t-tests, one-way ANOVA, and Pearson’s correlation. Reference intervals (RIs) were calculated following CLSI C28-A3 guidelines. Results The mean global pRNFL thickness was 95.34 ± 8.83 µm in the right eye (OD) and 95.04 ± 8.65 µm in the left eye (OS). The 95% RI was 79.00–116.00 µm (OD) and 79.47–113.52 µm (OS). Quadrant distribution followed the ISNT rule (Inferior > Superior > Nasal > Temporal). Females demonstrated significantly thicker pRNFL than males (p < 0.01). A significant age-related decline in pRNFL thickness was observed (p < 0.001), particularly in those ≥ 40 years. pRNFL thickness correlated strongly and positively with neuroretinal rim area (p < 0.001) and negatively with average cup-to-disc ratio and cup volume (p < 0.05). Conclusions This study establishes the first large-scale normative pRNFL database for Omani adults. The findings highlight that age and sex are significant determinants of thickness, emphasizing that population-specific, adjusted reference values are essential for accurate OCT interpretation. Integrating these localized data into clinical practice can reduce diagnostic misclassification, such as "red disease", and enhance the detection of glaucoma and other optic neuropathies in this population.