AQP4 and neuromyelitis optica: The loss of pRNFL thickness in the placebo group at 6 months was consistent with previous natural history studies of AON.13,14 Care was taken to exclude patients with atypical AON (none of the participants had serum aquaporin-4 antibodies), and no participants developed features of disorders such as neuromyelitis optica or chronic relapsing inflammatory optic neuropathy.