1 Francis I. Proctor Foundation for Research in Ophthalmology and the Department of Ophthalmology, University of California, San Francisco School of Medicine, San Francisco, California.
2 Francis I. Proctor Foundation for Research in Ophthalmology and the Department of Ophthalmology, University of California, San Francisco School of Medicine, San Francisco, California. Electronic address: tom.lietman@ucsf.edu.