Low Hyperopic Spherical Equivalent and Peripapillary Retinal Nerve Fiber Layer Thickness: A Quadrant-specific Mixed-effects Analysis

Background: Refractive status is known to influence optical coherence tomography (OCT) measurements of the peripapillary retinal nerve fiber layer (RNFL). This pilot study aimed to evaluate the association between low hyperopic spherical refractive error and quadrant-specific peripapillary RNFL thickness in a young population. Materials and Methods: This institutional cross-sectional pilot study included 36 consecutive participants (72 eyes) aged 8–25 years with low hyperopia (mean spherical error: +0.52 ± 0.28 D; range: +0.10–+1.00 D). Peripapillary RNFL thickness was measured using spectral-domain OCT. Mixed-effects linear regression, with subject as a random effect, was used as the primary analytic approach to account for intereye correlation. Supplementary Pearson correlation analyses were also performed. Results were interpreted using a Bonferroni-adjusted reference threshold of α =0.01. Results: The mean age of participants was 16.6 ± 4.8 years. Mixed-effects regression demonstrated a positive association between spherical refractive error and RNFL thickness in the superior ( P = 0.0003), temporal ( P = 0.005), inferior ( P = 0.016), and nasal ( P = 0.021) quadrants. Pearson analyses similarly showed positive correlations in the superior (r = 0.422, P = 0.0002), temporal (r = 0.336, P = 0.004), inferior (r = 0.287, P = 0.014), and nasal (r = 0.277, P = 0.019) quadrants. After Bonferroni adjustment, associations remained significant in the superior and temporal quadrants, while inferior and nasal findings were exploratory. Average RNFL thickness showed a nonsignificant positive trend. Conclusion: Low hyperopic refractive error was associated with a modest increase in peripapillary RNFL thickness, most consistently in the superior quadrant. These findings suggest that refractive status may influence OCT-based RNFL interpretation even in near-emmetropic eyes. However, given the limited sample size, these results should be considered exploratory and hypothesis-generating.