Variability in Optic Nerve Head Morphology in High Axial Myopia and Its Association with Glaucoma

Abstract

Purpose: To investigate optic disc morphology in high axial myopia and its associations with the deep-layer structure of the optic disc using optical coherence tomography and glaucoma.Methods: We retrospectively reviewed the medical records of 69 eyes (33 normal and 36 glaucomatous eyes) with an axial length of 26-27 mm. The eyes were categorized into two groups based on the optic disc tilt ratio (≥ 1.3 or < 1.3). Characteristics of optic disc morphology, including lamina cribrosa depth, peripapillary atrophy width, and Bruch’s membrane opening area, were compared between the two groups. Furthermore, factors related to mean deviation and global retinal nerve fiber layer (RNFL) thickness were analyzed.Results: The mean optic disc tilt ratio was 1.31 ± 0.23. Eyes with a tilt ratio ≥ 1.3 (30 eyes) had a higher likelihood of glaucoma (<i>p</i> = 0.035) and severe visual field (VF) defects (<i>p</i> < 0.001), a thinner global RNFL thickness (<i>p</i> = 0.046), and larger gamma peripapillary atrophy width (<i>p</i> < 0.001) compared to eyes with a tilt ratio < 1.3 (39 eyes). Linear regression analysis revealed that the optic disc tilt ratio was significantly associated with VF loss (<i>p</i> = 0.018) but not with global RNFL thinning (<i>p</i> = 0.203).Conclusions: Variations in optic disc morphology are observed in eyes with similar axial lengths, and a higher optic disc tilt ratio is associated with more severe VF defects. These findings suggest the potential influence of optic disc morphological changes due to axial elongation on the severity of glaucomatous damage.