Comparison of Retinal Nerve Fibre Layer versus Bruch Membrane Opening-Minimum Rim Width as an Optical Coherence Tomography-based Marker for Glaucoma in Myopia.

Objective: To compare the reliability of Bruch Membrane Opening-Minimum Rim Width (BMO-MRW) Optical Coherence Tomography (OCT) with Retinal Nerve Fibre Layer (RNFL) in myopic patients.

Study Design: Cross-sectional study.

Place And Duration Of Study: LRBT Free Base Eye Hospital, Karachi, from May 2019 to July 2020.

Methodology: Moderate myopes with refractive errors between -3 to -6 diopters were examined by 2 glaucoma consultants separately, who performed fundoscopy to evaluate the optic nerve head, checked IOP and assessed CCT and visual fields to stratify the eyes into myopic normal and myopic glaucomatous eyes. All eyes were imaged with SD OCT of Spectralis version 1.10.2.0 of Heidelberg Engineering. Two scanning patterns, one for BMO-MRW and the other for RNFL thickness analysis, were performed.

Results: Fifty eyes of 50 patients were diagnosed with glaucoma in 50% (25 out of 50 patients). OCT RNFL detected glaucoma in 72% (36 out of 50 patients). While OCT BMO-MRW detected glaucoma in 56% (28 out of 50 patients). There was strong agreement between the consultant's judgements and BMO-based test (κ = 0.800, p <0.001), but the association was comparatively weaker with RNFL-based prediction (κ = 0.480, p <0.001). Specificity was better with OCT BMO-MRW (85.7%) than RNFL (66.7%). There were lower false positive rates with BMO-MRW (14.3%) than RNFL (33.3%).

Conclusion: OCT BMO-MRW is a better indicator of glaucomatous damage in moderately myopic eyes as compared to OCT RNFL analysis. Key Words: Glaucoma, Myopia, Optical Coherence Tomography (OCT), Bruch Membrane Opening-Minimum Rim Width (BMO-MRW), Retinal Nerve Fibre Layer (RNFL).