Diabetic retinopathy (DR) is a leading cause of vision loss in the United States and occurs as a result of pathologic changes of the retinal vasculature. In 2005-2008, the estimated crude prevalence among Americans over the age of 40 with diabetes was 28.5 percent. Although the prevalence of vision-threatening DR is approximately 4.4 percent, the number of affected Americans 40 years or older is expected to triple from 1.2 million in 2005 to 3.4 million...