1. From the Departments of Ophthalmology (V.P.D., K.A.A.D., B.K.C.) and Radiology (K.L.R.), Massachusetts Eye and Ear Infirmary, Harvard Medical School, 243 Charles St, Boston, MA 02114; and Department of Neurology, Neuro-Ophthalmology Service, Massachusetts General Hospital, Harvard Medical School, Boston, Mass (B.K.C.).