Impact of the anti-aquaporin-4 autoantibody on inner retinal structure, function and structure-function associations in Japanese patients with optic neuritis.

PURPOSE: An autoantibody against aquaporin-4 (AQP4 Ab) is highly specific for neuromyelitis optica spectrum disorder and plays a pathogenic role in this disease. The purpose of this study was to investigate the impact of AQP4 Ab on inner retinal structure, function, and the structure-function relationships in eyes with optic neuritis.

METHODS: Thirty five eyes from 25 cases who had received visual function tests and RTVue optical coherence tomography (OCT) measurement at least six months after the latest episode of optic neuritis were enrolled. Patients with multiple sclerosis were excluded. AQP4 Ab was measured using a cell-based assay. Visual acuity, mean deviation (MD) of the Humphrey visual field SITA standard 30-2 tests, retinal nerve fiber layer (RNFL), ganglion cell complex (GCC) thicknesses, and other clinical variables were compared between the AQP4 Ab-positive and -negative groups. Parameters associated with visual functions were evaluated by generalized estimating equation (GEE) models.

RESULTS: The AQP4 Ab-positive group (20 eyes from 12 cases) had a higher proportion of bilateral involvement and longer duration of follow-up than the AQP4 Ab-negative group (15 eyes from 13 cases). Linear mixed effect models revealed worse MD and visual acuity in AQP4 Ab-positive eyes than those in AQP4 Ab-negative eyes after adjusting for within-patient inter-eye dependence, whereas there were no differences in RNFL and GCC thickness between the two groups. In seropositive eyes, GEE regression analyses revealed that depending on age and the number of recurrences of ON episodes, OCT parameters correlated strongly with MD and more weakly with visual acuity.

CONCLUSIONS: Reductions in RNFL and GCC thickness were proportional to the visual field defect in eyes with AQP4 Ab but not in eyes without AQP4 Ab. The presence of AQP4 Ab probably plays a critical role in retinal ganglion cell loss in optic neuritis.