Retinal Nerve Fiber Layer Thickness/Minimum Rim Width Ratio Differentiates Glaucoma From Other Optic Neuropathies

Area of Science:

• Ophthalmology
• Neuroscience
• Medical Imaging

Background:

• Glaucomatous optic neuropathies (GONs) and non-GONs (NGONs) share optic nerve head pathologies.
• Distinguishing GONs from NGONs is crucial for accurate diagnosis and treatment.
• The peripapillary retinal nerve fiber layer thickness (pRNFL) and Bruch membrane opening-minimum rim width (BMO-MRW) are key structural parameters.

Purpose of the Study:

• To evaluate the diagnostic capability of the global pRNFL/BMO-MRW ratio in differentiating GONs from NGONs.
• To compare the diagnostic accuracy of the pRNFL/BMO-MRW ratio with individual pRNFL and BMO-MRW measurements.
• To identify specific markers indicative of glaucoma within the optic nerve head.

Main Methods:

• A retrospective study of 171 patients with optic neuropathy and visual loss >6 months.
• Measurement of pRNFL thickness and BMO-MRW using spectral-domain optical coherence tomography.
• Evaluation of diagnostic accuracies using areas under receiver operating characteristic curves (AUC).

Main Results:

• The global pRNFL/BMO-MRW ratio demonstrated the highest AUC (0.97) for distinguishing GONs from NGONs.
• A cutoff value of 0.34 for the ratio effectively separated GONs and NGONs.
• Increased visual field defect severity correlated with a higher ratio in GONs and a lower ratio in NGONs.

Conclusions:

• The global pRNFL/BMO-MRW ratio is a highly effective parameter for differentiating GONs from NGONs.
• Lower BMO-MRW, even with similar pRNFL thinning, is a specific indicator of glaucoma.
• These findings highlight distinct neuroglial architecture changes in glaucoma, supporting fundamental pathophysiological differences.