AQP4 and myeloid sarcoma: Based on retrospective analysis of 11 studies (not all of which distinguished between AQP4-IgG-positive and AQP4-IgG-negative patients), OCT shows average RNFL thinning after ON to 55–83 μm in NMOSD and 74–95 μm in MS, compared to an average RNFL thickness of 93–108 μm in healthy individuals without a history of ON [12]; more profound RNFL atrophy (especially in non-temporal quadrants) than in MS has also been demonstrated in MOGAD in a recent pediatric cohort after the first ON attack [155].