AQP4 and optic neuritis: In a previous study, the thinning of the inner retinal layer in eyes with MS and NMOSD was explained by retrograde degeneration due to optic neuritis or subclinical optic neuritis.[13] The results of our study suggest a pathology independent of retrograde degeneration, and the results suggest a primary retinal pathology including a direct attack of the retina by anti-AQP4 antibody (Fig 4).