[1] Univ Maryland, Med Ctr, Dept Neurol, Baltimore, MD 21201 USA
[2] Univ Maryland, Sch Med, Dept Neurol, Baltimore, MD 21201 USA
[3] Univ Maryland, Sch Med, Dept Ophthalmol & Visual Sci, Baltimore, MD 21201 USA
[4] Univ Penn, Dept Neurol, Perelman Sch Med, Philadelphia, PA 19104 USA