The following is the summary of “Retinal Nerve Fibre Layer Thickness/Minimum Rim Width Ratio Differentiates Glaucoma From Other Optic Neuropathies,” published in the May 2023 issue of Glaucoma by Boussion, et al.
One objective and valuable metric for distinguishing glaucomatous optic neuropathies (GONs) from non-GONs (NGONs) is the ratio of global peripapillary retinal nerve fiber layer thickness (pRNFL) to Bruch membrane opening-minimum rim width (BMO-MRW).
This research was conducted to assess the diagnostic value of the pRNFL/BMO-MRW ratio in distinguishing GONs from NGONs. Patients having a single proven etiology for their visual impairment due to optic neuropathy (ON) were included in this retrospective analysis.
Spectral-domain optical coherence tomography (Spectralis, Heidelberg Engineering, Heidelberg, Germany) was used to assess pRNFL thickness and BMO-MRW. Areas under receiver operating characteristics curves were used to compare the diagnostic accuracy of pRNFL, BMO-MRW, and the global pRNFL/BMO-MRW ratio. The eyes of 171 individuals were examined; of those, 50 had primary open-angle glaucoma, 15 had normal pressure glaucoma, 50 had optic neuritis, 15 had nonarteritic anterior ischemic optic neuropathy, 24 had compressive optic neuropathy, 10 had dominant optic atrophy, and 7 had nutritional optic neuropathy.
The area under the receiver operating characteristics curve was the largest for the worldwide pRNFL/BMO-MRW ratio [0.97 vs. 0.92; P=0.01]. A threshold value of 0.34 was used to separate GONs from NGONs successfully. The ratio was larger for GONs and lower for NGONs as the mean deviation of the visual field-defect severity increased. MRW was identified as a glaucoma-specific marker, demonstrating the neuroglial architectural changes within the optic nerve head typical of glaucoma and supporting fundamental pathophysiological differences when compared with NGONs for the same degree of pRNFL thinning.