Optical coherence tomography helps differentiate neuromyelitis optica and MS optic neuropathies

OBJECTIVE: To evaluate the retinal nerve fiber layer (RNFL) thickness and macular volume in neuromyelitis optica (NMO) spectrum patients using optical coherence tomography (OCT). BACKGROUND: OCT can quantify damage to retinal ganglion cell axons and can identify abnormalities in multiple sclerosis and optic neuritis (ON) eyes. OCT may also be useful in the evaluation of patients with NMO. METHODS: OCT and visual function testing were performed in 26 NMO spectrum patients with a history of ON, 17 patients with isolated longitudinally extensive transverse myelitis (LETM) without ON, 378 patients with relapsing-remitting multiple sclerosis (RRMS), and 77 healthy controls at 2 centers. RESULTS: Substantial RNFL thinning was seen in NMO ON eyes (63.6 μm) relative to both RRMS ON eyes (88.3 μm, p < 0.0001) and control eyes (102.4 μm, p < 0.0001). A first episode of ON was estimated to cause 24 μm more loss of RNFL thickness in NMO than RRMS. Similar results were seen for macular volume. ON also was associated with more severe visual impairment in NMO spectrum patients than in RRMS patients. Eyes in the LETM group and unaffected NMO eyes were not significantly different from controls, though conclusions about these subgroups were limited by small sample sizes. CONCLUSIONS: Optical coherence tomography (OCT) shows more severe retinal damage after optic neuritis (ON) episodes in neuromyelitis optica (NMO) than in relapsing-remitting multiple sclerosis. Identification of substantial retinal nerve fiber layer loss (>15 μm) after ON in a non-multiple sclerosis patient should prompt consideration of an NMO spectrum condition. OCT may be a useful tool for the evaluation of patients with NMO.