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

PRCIS: Global peripapillary retinal nerve fiber layer thickness (pRNFL)/Bruch membrane opening-minimum rim width (BMO-MRW) ratio is an objective and effective parameter to separate glaucomatous optic neuropathies (GONs) from nonGONs (NGONs).

PURPOSE: This study was undertaken to evaluate the diagnostic capability of the pRNFL/ BMO-MRW ratio to differentiate GONs from NGONs.

PATIENTS AND

METHODS

This retrospective study included patients with an optic neuropathy (ON), visual loss for>6 months and a confirmed single etiology. pRNFL thickness and BMO-MRW were measured with spectral-domain optical coherence tomography (Spectralis, Heidelberg Engineering, Heidelberg, Germany). The diagnostic accuracies of pRNFL, BMO-MRW and the global pRNFL/BMO-MRW ratio were evaluated with the areas under receiver operating characteristics curves.

RESULTS

One eye each from 171 patients was investigated: 50 primary open angle glaucomas, 15 normal pressure glaucomas, 50 optic neuritises, 15 nonarteritic anterior ischemic ONs, 24 compressive ONs, 10 dominant optic atrophies, and 7 nutritional ONs. The global pRNFL/BMO-MRW ratio had the highest area under receiver operating characteristics curve [0.97 vs. 0.92; P =0.01]. It was able to distinguish between GONs and NGONs with a cutoff value of 0.34. Increased mean deviation of the visual field-defect severity was associated with a higher ratio for GONs and a lower ratio for NGONs.

CONCLUSION

Compared with NGONs and for the same degree of pRNFL thinning, lower BMO- MRW was found to be a specific marker of glaucoma, reflecting the neuroglial architecture changes within the optic nerve head typical of glaucoma and supporting fundamental pathophysiological differences.