Background: Neuromyelitis optica spectrum disorder-optic neuritis (NMOSD-ON) can now be distinguished from other types of ON as a specific disease by the Aquaporin-4 antibody (AQP4-Ab) test. NMOSD-ON can cause severe retinal nerve fiber layer (RNFL) damage. The optical coherence tomography (OCT) characteristics between NMOSD- ON and idiopathic optic neuritis (IDON) were seldom studied in Asians.
Methods: This prospective case-control study involved 152 eyes from 143 optic neuritis (ON) patients. All the patients were divided into either the NMOSD-ON group or the IDON group based on the AQP4-Ab test. The retinal nerve fiber layer thickness (RNFLT), retinal thickness (RT), and choroidal thickness (CT) were measured by spectral-domain OCT and compared to the 60 age- and gender-matched healthy controls. The association between RNFLT and best corrected visual acuity (BCVA) was examined.
Results: The RNFLT was significantly thinner in all ON patients than in healthy controls, while NMOSD-ON eyes were significantly more affected than IDON eyes in all quadrants (p < 0.01). NMOSD-ON patients had stronger visual function impairment than IDON patients (p < 0.01). RNFLT was related to BCVA in both the NMOSD-ON and IDON groups. Microcystic macular edema (MME) was identified in 28 patients (19.58%) and in 29 of 152 eyes (19.08%), including 20 of 40 eyes (50%) previously affected by ON. MME was more common in patients with NMOSD-ON (32.2%) than in those with IDON (10.75%) (p = 0.001).
Conclusions: The NMOSD-ON group had more pronounced RNFLT thinning and visual function impairment than the IDON group. MME prevalence was higher in NMOSD-ON and was associated with higher frequency of clinical relapses.
Keywords: Neuromyelitis optica; Optic neuritis; Optical coherence tomography; Retinal nerve fiber layer.