National Eye Institute: "Facts About Diabetic Eye Disease."<br> Mayo Clinic, Patient Care & Health Information, Diseases & Conditions: "Diabetic retinopathy."<br> American Optometric Association, Glossary of Common Eye & Vision Conditions: "Diabetic Retinopathy."<br> American Academy of Ophthalmology: "What Is Macular Edema?"<br> National Eye Institute: "Facts About Macular Edema."