Bruch’s membrane opening minimum rim width and peripapillary retinal nerve fibre layer thickness measurement in myopic eyes with glaucoma

Abstract

Introduction: Optic nerve head imaging in myopic eyes with glaucoma is challenging due to atypical myopic optic disc morphology. Peripapillary retinal nerve fibre layer (pRNFL) and Bruch’s membrane opening-minimum rim width (BMO-MRW) utilize different anatomical reference points to measure the retinal nerve fibre layer. Purpose: To evaluate the diagnostic agreement between BMO-MRW and pRNFL in glaucomatous eyes with varying degrees of myopia. Design: Prospective observational study. Methods: Forty-three eyes diagnosed as primary open-angle glaucoma, normal-tension glaucoma, and primary angle-closure glaucoma with varying degrees of myopia were included in the study. Geometric measurement of the neuroretinal rim tissue was conducted with spectral domain optical coherence tomography (SD-OCT) usingtwo different parameters: BMO-MRW and pRNFL. The classification of scan quality and diagnostic agreement between both methods were compared using an exact McNemar’s test. The association between the summary classifications of quality scans with myopic degree was assessed with Fisher’s exact test. Results: BMO-MRW had a higher percentage of good quality image scans compared to pRNFL (p = 0.004). BMO-MRW was capable of obtaining equally good quality scans for glaucomatous eyes with various myopic degrees, whereas pRNFL demonstrated a significant statistical difference between mild, moderate, and high myopia(p = 0.001). pRNFL was difficult to identify in highly myopic eyes. By excluding poor quality scans, the diagnostic agreement between both modalities was 48.4% (p = 0.002). The observed agreement was higher in low myopia (66.7%), followed by moderate myopia (28.6%) and high myopia (16.7%). Conclusion: Compared to pRNFL, BMO-MRW is a better diagnostic imaging modality in glaucoma, especially for eyes with high myopia. Scan quality must be considered when interpreting OCT result in daily clinical practice to yield more accurate and reliable results.