Lesion length of optic neuritis impacts visual prognosis in neuromyelitis optica.

Objectives: The visual acuity prognoses of patients with neuromyelitis optica (NMO) are worse than those with optic neuritis (ON) caused by other diseases. Predicting the prognoses of ON at the time of onset is important for selecting treatments for NMO patients.

Methods: Twenty-three consecutive anti-aquaporin-4 autoantibody-positive NMO patients who presented with ON and had contrast-enhanced optic MRIs in the acute phase of their first ON episode were examined. Optical coherence tomographies (OCTs) were also examined for 22 of them. The visual acuity at the final follow-up, as assessed with the logMAR scale more than three years after ON onset, served as the outcome measure. These variables were also collected from 12 patients with serum anti-myelin oligodendrocyte glycoprotein antibody (anti-MOG-Ab).

Results: The strongest predictor of visual prognosis was the axial ON lesion length in the acute phase (R=0.747, p<0.0001), which was not observed in patients with anti-MOG-Ab. Specifically, the ON lesion length within the intra-orbit and canalicular segments exhibited the strongest correlation with visual prognosis (R=0.783, p<0.0001). The ON onset age was also correlated with visual prognosis (R=0.435, p=0.0338). OCT data in the chronic phase also showed a correlation with visual prognosis, but they were much weaker than the ON lesion length in the acute phase.

Conclusions: The ON lesion length in the acute phase was an important predictor of the visual prognoses of NMO patients.