1. Department of Veterans Affairs, Iowa City Health Care System, Iowa City, IA, USA;
2. Department of Internal Medicine, University of Iowa, Iowa City, IA, USA;
3. College of Pharmacy, University of Iowa, Iowa City, IA, USA;
4. Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, IA, USA;
5. Veterans Affairs Center for the Prevention and Treatment of Visual Loss, Iowa City, IA, USA