1. Research Division, Joslin Diabetes Center, Boston, MA 02215, USA.
2. Beetham Eye Institute, Joslin Diabetes Center, Boston, MA 02215, USA.
3. California Retina Consultants, Santa Barbara, CA 93103, USA.
4. Department of Medicine, Harvard Medical School, Boston, MA 02115, USA.
5. Center for Translational Vision Research, Gavin Herbert Eye Institute, Irvine, CA 92697, USA.
6. Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.