AQP4 and neuromyelitis optica: Although AQP4 played a vital role in the pathogenesis of NMO and NMOSD, in the present study, we found that the AQP4-Ab concentration in serum had no association with optic nerve alterations or macula before standard steroid treatment when age, gender and BCVA were controlled in AQP4-Ab-positive ON eyes (Fig 5).