Factors influencing glaucoma severity in highly myopic glaucoma

To investigate optic nerve head (ONH) parameters in highly myopic individuals with open-angle glaucoma (OAG) and their associations with glaucoma severity. A total of 132 patients with highly myopic OAG (132 eyes) who underwent ophthalmic examinations between January 2022 and December 2023 were included in this cross-sectional study. Patients were categorised into mild, moderate or advanced glaucoma groups based on the International Classification of Diseases 10th criteria. ONH parameters were measured, including disc area, tilt angle, β-zone and γ-zone parapapillary atrophy (PPA) areas and lamina cribrosa (LC) metrics. These parameters were compared across severity groups using analysis of variance. Pearson's correlation and linear regression analyses were conducted, adjusting for axial length (AXL). Structural equation modelling (SEM) was performed to explore pathways among ONH parameters and glaucomatous damage. The mild, moderate and advanced glaucoma groups comprised 31, 42 and 59 patients, respectively. The mild group showed shorter AXL than the other groups (26.29 (0.85) vs 27.35 (1.35) and 27.07 (1.17) mm; p=0.001) and exhibited lower disc ovality index, tilt angle, β-zone PPA area, β-zone PPA-to-disc area ratio and PPA radial extent (all p<0.05). Multivariate regression revealed the association of β-zone PPA area with average ganglion cell-inner plexiform layer (GCIPL) thickness (β=-1.162, p=0.029). SEM identified a significant pathway linking disc tilt angle, LC depth, GCIPL thinning and visual field loss. Mild group showed less ONH deformation and shorter AXL. Both regression and SEM analyses support the role of ONH structural changes-particularly β-zone PPA and disc tilt-in influencing glaucomatous damage in highly myopic eyes.