1. Department of Ophthalmology, Walter Reed National Military Medical Center , Bethesda, MD 20814, USA
2. Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences , Bethesda, MD 20814, USA
3. Department of Ophthalmology, Brooke Army Medical Center , San Antonio, TX 78219, USA
4. Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc. , Bethesda, MD 20817, USA