Greater exposed neural canal elongation of the myopic optic nerve head is associated with papillomacular bundle defects in glaucoma.

Abstract

To investigate the association between optical coherence tomography (OCT) parameters of optic nerve head (ONH) neural canal configuration and papillomacular bundle (PMB) defects in myopic eyes with glaucoma. Retrospective cross-sectional study. Patients with myopia and normal-tension glaucoma (NTG). Enhanced depth imaging OCT of the ONH was performed. Quantitative measurements of the exposed neural canal (ENC) configuration included border tissue lengths and conjugate opening areas defined by the Bruch's membrane opening (BMO), anterior scleral canal opening (ASCO), and scleral flange opening (SFO). Associations between the ONH OCT parameters and the presence of PMB defects. In this cohort, the mean axial length was 26.52 ± 1.10 mm (range, 24.30 to 29.25 mm), and PMB defects were observed in 37 of 101 eyes (36.6%). Longer externally oblique border tissue (EOBT) and externally oblique choroidal border tissue (EOCBT) length ratios relative to the BMO diameter, measured along the axis of maximal EOBT length, as well as lower BMO-ASCO and BMO-SFO conjugate area ratios normalized to the BMO area, were significantly associated with the presence of PMB defects after adjusting for age and axial length (all P < .05). Notably, PMB defects were present in 75.0% of eyes with EOBT ratios ≥ 0.5 and in 66.7% of eyes with BMO-SFO conjugate area ratios < 0.5. Greater ENC elongation in the myopic ONH, most pronounced in the temporal and inferotemporal regions corresponding to the PMB trajectory, was associated with PMB defects in glaucoma.