Bruch's membrane opening minimum rim width provides objective differentiation between glaucoma and non-glaucomatous optic neuropathies.

Abstract Purpose A challenging clinical scenario is distinguishing between normal tension glaucoma (NTG) and non-glaucomatous optic neuropathies (NGON). Key to the assessment remains assessing for the presence of optic nerve head cupping. Recent optical coherence tomography (OCT) measures now allow objective assessment of cupping by BMO-MRW. This study assessed the hypothesis that the BMO-MRW measurement quantifies cupping, and therefore can differentiate between NTG and NGON. Design Diagnostic evaluation with area under the curve Methods . Setting Multicentre tertiary hospitals and outpatient clinics Patient population 81 eyes of 81 patients were enrolled, 27 with NTG and 54 with NGON including ischemic optic neuropathy, previous optic neuritis, and compressive and inherited optic neuropathies. All NGON patients with intraocular pressure > 21mmHg, narrow drainage angles or a family history of glaucoma were excluded. Observational procedure Optic disc OCT was obtained of both the RNFL thickness and the BMO-MRW. Main Outcome Measures The utility of the BMO-MRW in differentiating GON from NGON was assessed using the area under the curve (AUC) estimated from a logistic regression model. Results The 5-fold cross validated AUC for glaucoma vs. non-glaucoma from logistic regression models using BMO-MRW values from all sectors was 0.95 (95% confidence interval: 0.86, 1.00). Conclusions The measurement of BMO-MRW effectively differentiates between NTG and NGON with a high level of sensitivity and specificity. Incorporating this measurement into routine glaucoma assessment may provide a robust method of assisting clinicians to improve diagnosis and therefore treatment of optic nerve diseases.