A Comparison of Retinal Nerve Fiber Layer Thickness and Bruch’s Membrane Opening-Minimum Rim Width Thickness Between Glaucoma and Disc-Suspect Patients Using Optical Coherence Tomography

TL;DR

This study compares two eye measurements, RNFLT and BMO-MRW, to see how well they can detect glaucoma and predict its progression in patients at risk.

Contribution

The study evaluates the diagnostic value of combining BMO-MRW and RNFLT measurements for early glaucoma detection and progression prediction.

Findings

Glaucoma patients had significantly thinner RNFLT and BMO-MRW compared to disc-suspect patients.

RNFLT was better at predicting visual field loss, while BMO-MRW detected subtle structural changes more precisely.

BMO-MRW and RNFLT showed positive agreement, suggesting their combined use improves diagnostic accuracy.

Abstract

Background

Glaucoma results in optic neuropathy, which is irreversible but can be treated effectively when diagnosed early. Several diagnostic parameters have been used to detect the functional and structural damage in glaucoma, which may go hand in hand or precede each other. Therefore, studying the functional and structural changes together may effectively improve the sensitivity and specificity of the diagnosis. In this study, we aim to compare Bruch’s membrane opening-minimum rim width (BMO-MRW) and retinal nerve fiber layer thickness (RNFLT) and assess their role in the diagnosis and prognosis of glaucoma.

Purpose

To compare RNFLT and BMO-MRW values between glaucoma and disc-suspect patients.

Methods

This is a comparative cross-sectional study involving 87 glaucoma patients and 88 disc suspects. A comprehensive ocular examination was performed for all patients, including best-corrected visual acuity (BCVA), intraocular pressure (IOP), and cup-to-disc ratio (CDR) assessment. Optical coherence tomography (OCT) was performed in all cases. We measured RNFLT and BMO-MRW in all quadrants. We used the Mann-Whitney test for intergroup and intragroup comparison, with a p-value <0.05 considered significant.

Results

The mean age was 57 years in the glaucoma group and 42 years in the disc suspect group. The differences in BCVA and CDR between the two groups were statistically significant. Most patients in both groups had BCVA between 6/12 and 6/6, and CDR between 0.5 and 0.7. The mean IOP was 19 mmHg in the glaucoma group, while it was 16 mmHg in disc suspects. Intragroup median RNFLT (glaucoma: 76 µm, disc suspects: 101 µm) and BMO-MRW (glaucoma: 202 µm, disc suspects: 254 µm) showed a significant difference in both groups. Intergroup comparison also showed a positive agreement between both parameters. RNFLT showed better predictability of associated visual field loss than BMO-MRW. In contrast, BMO-MRW was better at detecting subtle structural changes in the retina with more precision than RNFL.

Conclusion

BMO-MRW measurements are positively associated with RNFLT. This helps in diagnosing glaucoma at an early stage and detecting its progression early as well. The technique of measuring BMO-MRW is noninvasive, which gives a more precise measurement of the neuroretinal rim. A combination of both parameters can help in early diagnosis as well as predict the early progression of glaucoma in patients susceptible to developing it.