A comparative optical coherence tomography study in neuromyelitis optica spectrum disorder and multiple sclerosis

Objectives: The aim of this study was to find, using spectral domain-optical coherence tomography (SD-OCT), retinal imaging biomarkers differentiating neuromyelitis optica spectrum disorder (NMOSD), multiple sclerosis (MS) and healthy controls (HCs). Materials and methods: The population was composed of patients with NMOSD (n=23) or MS (n=110) and of HCs (n=75). Evaluation criteria were retinal thickness/volume, visual acuity, low contrast vision acuity and Expanded Disability Status Scale score. Results: Considering all eyes and after statistical adjustments including the number of optic neuritis (ON) episodes, we found that NMOSD patients did not have significantly more retinal atrophy than MS patients; whereas MS non-optic neuritis (NON) eyes had thinner temporal (p=0.032) and temporo-superior peripapillary retinal nerve fibre layer (pRNFL; p=0.011) thicknesses than NMOSD NON eyes; in addition, NMOSD NON eyes presented significant naso-inferior pRNFL (p=0.024), temporal pRNFL (p=0.039), macular ganglion cell complex (p=0.004) and ganglion cell layer (p=0.002) atrophy vs HC eyes. We identified significant correlations between visual and clinical disability and retinal thicknesses in both diseases. Conclusion: OCT may help to differentiate NMOSD and MS by focusing on the NON eyes (temporal pRNFL atrophy more severe in MS). Moreover, we discuss the possibility of a retinal degenerative process independent of ON in NMOSD.