Diabetic Eye Disease
A yearly exam for diabetic changes in the eye is recommended to detect the treatable causes of vision loss, sometimes before the patient is aware of symptoms.
Diabetes can affect all parts of the eye. Here are some of the more common ways it does so:
Diabetic retinopathy is a complication of diabetes that results from damage to the blood vessels of the light-sensitive tissue at the back of the eye (retina). At first, diabetic retinopathy may cause no symptoms or only mild vision problems. Eventually, however, diabetic retinopathy can result in blindness. In the United States, diabetic retinopathy is a leading cause of blindness in adults.
Diabetic retinopathy can happen to anyone who has diabetes, whether Type 1 (insulin-dependent) or Type 2 (usually diet- or oral-medication dependent) diabetes. In fact, up to 45 percent of adults diagnosed with diabetes in the United States have some degree of diabetic retinopathy, according to the National Eye Institute.
Diabetic retinopathy can happen to anyone who has diabetes. Risk factors for diabetic retinopathy include:
• Length of time you have had diabetes. The longer you have diabetes, the more likely you are to develop diabetic retinopathy. About 50% of diabetics who have had the disease for 15 years will show some signs of diabetic retinopathy.
• Poor control of your blood sugar. More effective control of blood sugar has been shown to decrease the progression of diabetic retinopathy.
• Hypertension, especially if your kidney function is compromised
• Pregnancy
• African or Latino origin
• Smoking
You can have diabetic retinopathy and not know it. In fact, symptoms are unusual in the early stages of diabetic retinopathy.
As the condition progresses, diabetic retinopathy symptoms may include:
• Spots floating in your vision
• Blurred vision
• Dark streaks or a red film that blocks your vision
• Poor night vision
• Vision loss
When you have diabetes, your body doesn't use sugar (glucose) properly. Either not enough insulin is present (as in Type 1 diabetes) or there is resistance to the effect of insulin (as in Type 2 diabetes). There are effects of sugar molecules attaching to proteins (advanced glycosylation end products, or AGEs) that cause the tissues to malfunction. For example, the smallest blood vessels may leak, or eventually close down from incorporation of AGEs in the walls of the vessels. If this happens in the retina, one might eventually develop edema, that is, fluid in the tissue spaces instead of within blood vessels or cells.
• Diabetic macular edema is the most common reason for vision loss in the diabetic population.
• The malfunction of diabetic blood vessels lead to the common “background” retinopathy: the arterioles (little arteries) can balloon out (microaneurysms), leak blood (dot and blot hemorrhages, retinal nerve fiber layer or “flame” hemorrhages), and leak lipid (the yellow splotches in the photo).
• Eyes with proliferative retinopathy are at higher risk for vision loss. With narrowing of the vascular walls from incorporation of the AGEs, the blood flow to the retina is compromised, as time goes on. Chemical signals are produced by the stressed tissue, and a complicated “call for help” results in the development of new blood vessels responding to the “need” for oxygen and nutrition. These new blood vessels, or neovascularization, mark an important transition of the diabetic retina into proliferative retinopathy. These eyes are at much higher risk for events that will result in severe visual loss: retinal hemorrhages that break through the surface, vitreous hemorrhages, scarring and contracture of the retina from overlying fibrovascular tissue, resulting in a retinal detachment.
Diabetic cataract can develop at an earlier age than usual. Its detection and treatment is the same as other cataracts. Your symptoms might include blur, glare, and loss of color vision.
Diabetic optic neuritis results from the closing of the tiny blood vessels in the nerve and is usually associated with poor circulation elsewhere.
Glaucoma, or elevated eye pressure associated with diabetes may be the result of new blood vessels (neovascularization) forming in the iris, releasing proteins and blood that clog up the meshwork (see Glaucoma), or causing the meshwork to scar close. Some studies have indicated that diabetes might be a risk factor for open angle glaucoma (OAG), but others have not.
Screening and Diagnosis
Diabetic eye disease can often be treated if detected early enough. A yearly, dilated eye exam is a good start. During this exam, the following steps are standard:
• Testing of vision and need for glasses
• Eye pressure check (tonometry), to detect glaucoma
• Slit lamp exam, to look for signs of glaucoma, cataract, iris neovascularization
• Retinal exam, to detect glaucoma, optic nerve disease, diabetic macular edema, and retinopathy.
Other specialized tests that might be useful in examining the diabetic eye include:
• Retinal photography, to detect and document even subtle changes in the retinal vasculature
• Fluorescein angiography, using a fluorescent dye that is injected into a vein in your arm. As the dye circulates through your eyes, a blue light causes the dye to light up, pinpointing blood vessels that are closed, broken down or leaking fluid.
• Optical coherence tomography (OCT), which provides cross-sectional images of the retina that show the thickness of the retina and whether fluid has leaked into retinal tissue. Later, OCT exams can be used to monitor treatment effectiveness.
Prevention
The longer you have diabetes, the greater your risk of developing diabetic retinopathy — but there's much you can do to promote healthy vision.
• Manage your diabetes. Make healthy eating and physical activity part of your daily routine. Take oral diabetes medications or insulin as directed.
• Monitor your blood sugar level. You may need to check and record your blood sugar level at least several times a day — or more if you're ill or under stress. Careful monitoring is the only way to make sure that your blood sugar level remains within your target range.
• Keep your blood pressure and cholesterol under control. High blood pressure and high cholesterol increase the risk of vision loss. Eating healthy foods, exercising regularly and losing excess weight can help. Sometimes medication is needed, too.
• If you smoke or use other types of tobacco, ask your doctor to help you quit. Smoking increases your risk of various diabetes complications, including diabetic retinopathy. Talk to your doctor about ways to stop smoking or to stop using other types of tobacco.
• Take stress seriously. If you're stressed, it's easy to abandon your usual diabetes management routine. The hormones your body may produce in response to prolonged stress may prevent insulin from working properly, which only makes matters worse. To take control, set limits. Prioritize your tasks. Learn relaxation techniques. Get plenty of sleep.
• Pay attention to vision changes. Yearly dilated eye exams are an important part of your diabetes treatment plan. Contact your eye doctor right away if you experience sudden vision changes or your vision becomes blurry, spotty or hazy.
Remember, diabetes doesn't necessarily doom you to poor vision. Taking an active role in diabetes management can go a long way toward preventing complications.
