Association of Optic Nerve Head Metrics and Parapapillary Gamma Zone With Myopia Onset and Progression in Children: The Hong Kong Children Eye Study.

Purpose: The purpose of this study was to evaluate the associations of optic nerve head (ONH) metrics and parapapillary gamma zone with myopia onset and progression in school children aged 6 to 8 years over a 3-year period. Methods: The ONH was imaged by spectral domain-optical coherence tomography (SD-OCT) using an adopted scan protocol comprising 24 equally spaced radial B-scans. Results: The study included 765 children (mean age = 7.69 ± 1.01 years, range = 6-8 years, refractive error = 0.33 ± 1.30 diopters [D] at baseline). Significant differences were found in disc ovality index, gamma zone area, Bruch's membrane opening distance (BMOD), temporal border tissue angle (BTA), and optic disc-fovea distance (DFD) across different refractive status groups (all P < 0.001). Multivariable logistic regression analysis indicated that female sex (odds ratio [OR] = 1.74, P = 0.006), longer axial length (OR = 1.81, P < 0.001), larger nasal BTA (OR = 1.01, P = 0.005), larger temporal BTA (OR = 1.01, P = 0.019), optic disc torsion (OR = 2.12, P = 0.007), and longer DFD at baseline (OR = 3.39, P < 0.001) were risk factors of myopia onset, whereas the presence of the gamma zone at baseline was not. In multivariable linear regression analysis, baseline disc ovality index, BMOD, nasal BTA, temporal BTA, and DFD, as well as changes in BMOD, nasal BTA, temporal BTA, gamma zone area, and DFD were significantly associated with spherical equivalent (SE) progression over 3 years. Conclusions: ONH parameters like nasal BTA, temporal BTA, disc torsion, and DFD may have predictive value for myopia onset and progression. As the myopic SE progresses, gamma zone enlargement coincides with the elongation of BMOD and DFD. It may be explained by an axial elongation-related Bruch's membrane opening shift into the temporal direction.