The characteristics of deep optic nerve head morphology in myopic normal tension glaucoma

PURPOSE. To investigate the relationship between axial length (AL) and deep optic nerve head (ONH) structure and to evaluate the characteristics of deep ONH structures in myopic normal tension glaucoma (NTG). METHODS. The following parameters were assessed using spectral-domain optical coherence tomography (SD-OCT): externally oblique border tissue (EOBT) length, ONH tilt angle, optic canal (OC) obliqueness, and b-zone peripapillary atrophy (PPA). In addition, the angular location of the maximal value of each parameter and retinal nerve fiber layer (RNFL) defect were measured using infrared and red-free photos. RESULTS. A total of 74 myopic NTG eyes and 67 myopic control eyes with a spherical equivalent < −0.5 diopters from 141 subjects were included. AL was correlated with the maximal values of EOBT length, ONH tilt angle, OC obliqueness, and β-zone PPA (P < 0.001, P = 0.003, P < 0.001, and P < 0.001, respectively). Multivariate logistic regression analysis revealed that temporally located maximal values of EOBT length, ONH tilt angle, and OC obliqueness were associated with the presence of myopic NTG (P = 0.014, P = 0.016, and P = 0.030, respectively). In myopic NTGs, RNFL defect locations were consistent with the locations of maximal values of EOBT length, ONH tilt angle, OC obliqueness, and β-zone PPA (P < 0.001, P < 0.001, P < 0.001, and P = 0.003, respectively). CONCLUSIONS. Temporalized angular locations of deep ONH parameters were associated with the presence of NTG in myopia. In myopic NTGs, the locations of deep ONH parameters were consistent with the locations of RNFL defect.