Regional Mechanical Asymmetry: A Key Feature of the Optic Nerve Head in High Myopia Associated with Structural Remodeling

Abstract Purpose To investigate regional mechanical asymmetry of the optic nerve head (ONH) in high myopia. Methods Swept-source OCT imaging was performed before and during controlled acute intraocular pressure (IOP) elevation. Three-dimensional strain was calculated using digital volume correlation, from which global strain (von Mises) and regional mechanical asymmetry (temporal–nasal strain gradient) were derived. Based on the measured strain response to IOP elevation, an effective, IOP-normalized Young’s modulus was estimated to characterize relative regional ONH tissue stiffness. Structural parameters included Bruch’s membrane opening area (BMOA), lamina cribrosa depth (LCD), gamma zone area, and BMO-minimum rim width. Results This study included 25 highly myopic eyes and 20 normal control eyes. The high myopia group exhibited larger BMOA and gamma zone area, as well as greater global strain (5.84 ± 1.47% vs. 4.84 ± 0.96%; p = 0.01) and T–N strain gradient (0.54 ± 0.38 vs. 0.19 ± 0.32; p < 0.01). Temporal ONH stiffness was significantly reduced relative to the nasal region. Multivariate analyses showed that the T-N strain gradient was independently associated with larger BMOA and gamma zone area, while global strain was associated with BMOA. A higher T-N strain gradient was also associated with greater LCD in univariate analysis. Conclusions Regional mechanical asymmetry is a key biomechanical feature of the highly myopic ONH and is independently linked to multiple aspects of structural remodeling. These findings highlight the role of regional mechanical asymmetry and suggest a potential biomechanical biomarker for early risk assessment in high myopia.