1 Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland.
2 Department of Epidemiology, UAB School of Medicine, Birmingham, Alabama.
3 Department of Ophthalmology, Walter Reed National Military Medical Center, Bethesda, Maryland; Department of Surgery, Uniformed Services University of Health Sciences, Bethesda, Maryland.
4 Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland. Electronic address: fworeta1@jhmi.edu.