An Evaluation of the Retinal Nerve Fibre Layer and Ganglion Cell Layer Thickness in Low Myopes

To evaluate the integrity of the peripapillary (pp) and macular (m) retinal nerve fibre layer (RNFL) and the macular ganglion cell layer (GCL) in young adults with low myopia.

The study was observational and cross-sectional in design. A total of 122 participants (61 emmetropes and 61 low myopes) were recruited, with a mean age 20.5 ± 1.86 years. Low myopia was defined as a spherical equivalent refraction (SER) between -0.75 and -3.00 D; controls had SER between +0.50 and -0.50 D. Refractive error was measured using the Essilor AKR550 Auto Kerato-Refractor. Axial length (AL) was assessed with the NIDEK AL-Scan Optical Biometer. Retinal layers were imaged using the Heidelberg Spectralis OCT, capturing macular RNFL (mRNFL), peripapillary RNFL (ppRNFL), Bruch's membrane opening-RNFL (BMO-RNFL) and macular GCL (mGCL) thickness. Independent t tests/Mann-Whitney Utests compared thicknesses; multivariate linear regression evaluated associations between AL, SER, RNFL and GCL measures. The Holm-Bonferroni correction was applied for all p values.

Mean SER was -0.25 ± 0.25 D (emmetropes) and -1.25 ± 0.57 D (low myopes); mean AL in the same groups was 23.41 ± 0.77 and 23.76 ± 0.82 mm, respectively. Low myopes showed significant thinning in the inferior (p = 0.03); Cohen's d effect size = -0.23 and temporal (p = 0.01); Cohen's d effect size = -0.61 regions of the outer mGCL. AL showed positive associations mostly with mRNFL and mGCL, although they were weaker in low myopes. Similarly, weaker positive correlations were also found in low myopes between AL and global ppRNFL (p = 0.02) when compared with near-emmetropes.

Significant differences in the inferior and temporal GCL layers in low myopes may suggest early structural changes. These findings highlight that myopia is not solely a refractive issue and suggest early intervention strategies may not be limited to high myopia cases.