Vol. 7, Issue 1, Part A (2025)

Introduction: Myopia is a significant risk factor for open-angle glaucoma, but diagnosing glaucoma in myopic patients remains challenging due to overlapping structural characteristics. Optical coherence tomography (OCT) is widely used to measure retinal nerve fiber layer (RNFL) thickness for glaucoma diagnosis; however, normative databases typically exclude individuals with high refractive errors. This study aimed to evaluate RNFL thickness in myopic patients compared to emmetropes and analyze quadrant-specific changes across varying degrees of myopia.

Methods: This cross-sectional observational study included 120 subjects (60 myopes, 60 emmetropes) aged 20-35 years attending ophthalmology OPD at BGS Global Institute of Medical Sciences Hospital. Comprehensive ophthalmic examination including refractive error measurement and RNFL thickness assessment using Cirrus HD Spectral Domain OCT was performed. Myopes were categorized as low (<-3D), moderate (-3D to-6D), and high (>-6D). Mean RNFL thickness was recorded globally and by quadrant.

Results: Mean RNFL thickness was significantly lower in myopes (85.78±11.04 μm) compared to emmetropes (100.22±7.17 μm; p<0.001) across all quadrants. Among myopes, significant differences were observed in average RNFL thickness by severity (low: 88.04±10.96 μm; moderate: 77.69±8.29 μm; high: 87.50±0.71 μm; p = 0.009), with significant variations in inferior (p = 0.004) and superior (p = 0.002) quadrants but not in nasal (p = 0.098) and temporal (p = 0.105) quadrants. Notable violation of the ISNT rule was observed particularly in moderate and high myopes. Gender did not significantly influence RNFL thickness in either myopic or emmetropic groups.

Conclusion: Myopia significantly affects peripapillary RNFL thickness measurements, with variations across different quadrants and degrees of myopia. The violation of the ISNT rule in moderate and high myopes highlights the importance of cautious interpretation of OCT measurements in myopic patients when screening for glaucoma and suggests the need for myopia-specific normative databases.