1. Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA, Department of Ophthalmology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
2. Department of Biostatistics, AMC Cancer Research Center, Denver, Colorado, USA
3. Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
4. Department of Neurology, Cleveland Clinic Foundation, Cleveland, Ohio, USA
5. Department of Neurology, University of Buffalo, Buffalo, New York, USA
6. Biogen, Fourteen Cambridge Center, Cambridge, Massachusetts, MA 02142, USA
7. Department of Ophthalmology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA, Department of Biostatistics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA