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Causes
By Mayo Clinic staff
Too much sugar in your blood can damage the tiny blood vessels (capillaries) that nourish the retina. This can result in diabetic retinopathy and vision loss. Elevated blood sugar levels can also affect the eyes' lenses. With high levels of sugar over long periods of time, the lenses can swell, providing another cause of blurred vision.
Diabetic retinopathy is usually classified as early or advanced.
- Early diabetic retinopathy. Nonproliferative diabetic retinopathy (NPDR) is the most common type of diabetic retinopathy. It can be described as mild, moderate or severe. When you have NPDR, the walls of the blood vessels in your retina weaken. Tiny bulges protrude from the vessel walls, sometimes leaking or oozing fluid and blood into the retina. These bulges are called microaneurysms. As the condition progresses, the smaller vessels may close and the larger retinal veins may begin to dilate and become irregular in diameter. Nerve fibers in the retina may begin to swell. Sometimes the central part of the retina (macula) begins to swell, too. This is known as macular edema.
- Advanced diabetic retinopathy. Proliferative diabetic retinopathy (PDR) is the most severe type of diabetic retinopathy. When you have PDR, abnormal blood vessels grow in the retina. Sometimes the new blood vessels grow or leak into the clear, jelly-like substance that fills the center of your eye (vitreous). Eventually, scar tissue stimulated by the growth of new blood vessels may cause the retina to detach from the back of your eye. If the new blood vessels interfere with the normal flow of fluid out of the eye, pressure may build up in the eyeball, causing glaucoma. This can damage the nerve that carries images from your eye to your brain (optic nerve).
- Preferred practice pattern: Diabetic retinopathy. American Academy of Ophthalmology. http://one.aao.org/CE/PracticeGuidelines/PPP_Content.aspx?cid=d0c853d3-219f-487b-a524-326ab3cecd9a. Accessed Dec. 14, 2009.
- Standards of medical care in diabetes, 2009. American Diabetes Association. Diabetes Care. 2009;32(suppl):13.
- Diabetic retinopathy. National Eye Institute. http://www.nei.nih.gov/health/diabetic/retinopathy.asp. Accessed Dec. 15, 2009.
- Diabetic retinopathy. American Optometric Association. http://www.aoa.org/diabetic-retinopathy.xml. Accessed Dec. 15, 2009.
- Fraser CE, et al. Prevention and treatment of diabetic retinopathy. http://www.uptodate.com/home/index.html. Accessed Dec. 14, 2009.
- Retinal detachment. National Eye Institute. http://www.nei.nih.gov/health/retinaldetach/retinaldetach.asp. Accessed Dec. 21, 2009.
- Robertson DM (expert opinion). Mayo Clinic, Rochester, Minn. Jan. 1, 2010.
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