1. From the Tavistock Intensive Care Unit (A.P.), The National Hospital for Neurology and Neurosurgery, and Department of Neuroimmunology, Institute of Neurology, Queen Square, London, UK; the Department of Neuroimmunology (G.K.), Institute of Neurology, Queen Square, London, UK; and the Colour and Vision Research Laboratories (T.L.S.; http://cvrl.ioo.ucl.ac.uk/index.htm), Institute of Ophthalmology, London, UK.