A previously healthy woman in her late 30 s presented with blurred vision in the right eye and an acute confusional state. Five months earlier she had experienced a self-limited right sixth-nerve palsy with paraesthesia of both arms; brain magnetic resonance imaging (MRI) had been interpreted as a first demyelinating event. Best-corrected visual acuity was 20/40 in the right eye and 20/25 in the left. Funduscopy of the right eye showed retinal whitening, oedema and flame-shaped haemorrhages along the superotemporal arcade (Fig.
