1. From the Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania; the
2. Department of Ophthalmology and The Charlie Mack Overstreet Laboratories for Retinal Diseases, University of Florida, Gainesville, Florida; and the
3. Howard Hughes Medical Institute and4Department of Ophthalmology, University of Iowa Carver College of Medicine, Iowa City, Iowa.