1. From the Departments of Ophthalmology and Visual Sciences and
2. the Department of Physiology and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio, Texas; and
3. The Jackson Laboratory, Howard Hughes Medical Institute, Bar Harbor, Maine.
4. From the Departments of Ophthalmology and Visual Sciences and 4Physiology, Moran Eye Center, University of Utah, Salt Lake City, Utah;