1. Wilmer Eye Institute, Johns Hopkins Medical Institutions, Baltimore, MD;
2. Department of Ophthalmology, University of Heidelberg, Heidelberg, Baden-Wuerttemberg, Germany;
3. Johns Hopkins School of Medicine, Baltimore, MD;
4. Department of Biostatistics, Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD; and
5. Johns Hopkins Disability Health Research Center, Johns Hopkins School of Nursing, Baltimore, MD.