Figure 1. Flowchart for Sampling of US Adults With Diabetic Retinopathy.
Diabetes was defined based on an algorithm developed by Varma et al. Specifically, individuals were classified as having diabetes if they self-reported a history of diabetes based on the question, “Have you ever been told by a doctor or health professional that you have diabetes or sugar diabetes?” Individuals were also categorized as having diabetes if they had a glycosylated hemoglobin A1c value of at least 6.5%, antidiabetic medication use according to the medication inventory file, or a positive response to the question “Are you now taking insulin?” or “Are you now taking diabetic pills to lower your blood sugar?” NHANES indicates National Health and Nutrition Examination Survey; NPDR, nonproliferative diabetic retinopathy; and PDR, proliferative diabetic retinopathy.