Sector-Specific Patterns of RNFL and Ganglion Cell Complex Thinning Across the Myopia Spectrum: A Cross-Sectional OCTA Study

Background and Objectives: Myopia is a rapidly growing global health burden driven primarily by axial elongation, which exerts mechanical stress on the inner retina, leading to progressive thinning of the retinal nerve fiber layer (RNFL) and the ganglion cell complex (GCC). The sector-specific pattern of these changes across the full spectrum of myopia remains incompletely characterized. This study aimed to provide a comprehensive, sector-level analysis of RNFL and GCC changes across four myopia severity grades using optical coherence tomography angiography (OCTA), and to quantify their correlations with axial length (AL) and central foveal thickness (CFD). Materials and Methods: A total of 260 eyes of 130 participants were enrolled in a prospective cross-sectional study. Eyes were classified into four groups: emmetropia (EM, n = 74), low myopia (LM, n = 68), moderate myopia (MM, n = 64), and high myopia (HM, n = 54). All participants underwent cycloplegic refraction, AL measurement, and RTVue XR Avanti OCTA imaging. RNFL thickness was assessed across five peripapillary sectors, and GCC thickness across twelve macular zones. Between-group differences were analyzed using one-way ANOVA with Bonferroni post hoc correction or Kruskal–Wallis/Dunn-Bonferroni tests. Pearson correlations were used to assess associations among structural parameters, AL, and CFD. Results: Both the RNFL and GCC showed progressive, statistically significant thinning with increasing myopia severity. The superior RNFL was the only peripapillary sector that differentiated EM from LM (p = 0.039), with total thinning of 18.8 μm from EM to HM. The paratemporal GCC zone showed the earliest macular structural signal (EM vs. LM, p = 0.049). Temporal and nasal RNFL sectors showed relative preservation, with differences restricted to comparisons involving HM. AL correlated negatively with the RNFL and GCC across all sectors (r = −0.46 to −0.71), with the strongest correlation observed for the superior RNFL in HM (r = −0.71, p < 0.001). CFD demonstrated progressively stronger coupling with GCC thickness as myopia severity increased, peaking in HM (r = 0.72, p < 0.001). Conclusions: The RNFL and GCC thinning in myopia follows a progressive, sector-specific pattern driven by axial elongation. The superior RNFL and paratemporal GCC are the earliest structural indicators of inner retinal change, detectable already at the low-myopia grade. These findings support a neural-first model of myopia-related retinal remodeling and advocate for multiparametric, stage-targeted structural monitoring in clinical practice.