1. Department of Ophthalmology, Duke University School of Medicine, Durham, North Carolina.
2. Department of Medicine, Durham VA Medical Center, Duke University School of Medicine, Durham, North Carolina.
3. Health Services Research & Development, Durham VA Medical Center, Durham, North Carolina.
4. Eshelman School of Pharmacy, Pharmaceutical Outcomes and Policy, University of North Carolina Chapel Hill, North Carolina.
5. Department of Biostatistics and Bioinformatics, Duke University School of Medicine, Durham, North Carolina.