References:

  1. National Institutes of Health. Diabetic retinopathy: causes and risk factors. NIHSeniorHealth website. http://nihseniorhealth.gov/diabeticretinopathy/causesandriskfactors/01.html. Accessed January 6, 2017.
  2. National Eye Institute. Facts about diabetic eye disease. https://www.nei.nih.gov/health/diabetic/retinopathy. Accessed January 6, 2017.