1. Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
2. Mailman School of Public Health, Columbia University, New York, NY 10032, USA
3. Division of Preventive Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02215, USA
4. Longitudinal Studies Section, Clinical Research Branch, National Institute on Aging, Baltimore, MD 21225, USA
5. Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA