Department of Epidemiology and Prevention, Division of Public Health Sciences, Wake Forest School of Medicine, Winston-Salem, North Carolina; Department of Ophthalmology, Wake Forest School of Medicine, Winston-Salem, North Carolina. Electronic address: egower@unc.edu. Department of Biostatistical Sciences, Division of Public Health Sciences, Wake Forest School of Medicine, Winston-Salem, North Carolina. National Eye Institute, National Institutes of Health, Bethesda, Maryland. Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, Wisconsin. Department of Epidemiology, University of Colorado School of Medicine, Aurora, Colorado. Department of Ophthalmology, Wake Forest School of Medicine, Winston-Salem, North Carolina.