Background: Neuromyelitis optica (NMO) is an inflammatory disease associated with optic neuritis and myelitis. Recently, several studies showed that optical coherence tomography (OCT) could be an interesting method for the evaluation of disease severity; however, to date there are no studies with a longitudinal follow-up of visual function in NMO. The aim of this study was to assess the ability of OCT to evaluate the progression of visual dysfunction in NMO.
Patients and methods: A group of 30 NMO patients (thus, 60 eyes), comprised of 20 women and 10 men with a mean age of 43.7 +/- 12.3 years, were prospectively evaluated clinically and by a whole neuro-ophthalmological work-up, including: visual acuity (VA), fundoscopy, visual evoked potential (VEP), visual field (VF) and optical coherence tomography (OCT). All patients were tested at baseline (after a mean disease duration of 6.1 years) and after a mean time of follow-up of 18 months (range: 12-36 months).
Results: Mean VA was similar at the two evaluation times (0.77 +/- 0.36 versus 0.77 +/- 0.35). The mean VF defect decreased slightly, but the difference was not significant (-5.9 +/- 1.3 dB versus -5.3 +/- 1.3 dB). In contrast, the mean retinal thickness seen on OCT decreased from 87.4 +/- 23.3 µm to 79.7 +/- 22.4 µm (p = 0.006). These modifications were only observed in eyes with a past or a recent history of optic neuritis (-15.1 µm; p < 0.001) and not in eyes without any history of optic neuritis (-2.4 µm; not significant). Also, they occurred independently of the occurrence of relapses (n = 13) and especially optic neuritis episodes; however, the number of optic neuritis episodes was low (n = 5).
Conclusion: OCT seems to be a more sensitive test than VA or VF for monitoring ophthalmological function in NMO and it seems to be helpful for the detection of infra-clinical episodes in patients with a past history of optic neuritis. Our results suggest that this easily performed technique should be used in the follow-up of NMO, but complementary studies are warranted to confirm its interest at an individual level.
Keywords: Neuromyelitis optica; longitudinal study; optic neuritis; optical coherence tomography; retinal thickness; visual dysfunction; visual tests.