Causes of Diabetic Retinopathy
In people with diabetes, high blood sugar damages the walls of the small blood vessels in the eye, altering their structure and function. These vessels may thicken, leak, develop clots, close off, or grow balloon-like defects called microaneurysms. Frequently, fluid accumulates in the part of the retina used in tasks such as reading; this condition is called macular edema. In advanced cases, the retina is robbed of its blood supply and grows new, but defective, vessels -- a process called neovascularization. These fragile vessels can bleed, creating vision-impairing hemorrhages, scar tissue, and separation of the retina from the back of the eye (retinal detachment). The new vessels can also block fluid flow within the eye, producing glaucoma.
Testing and Diagnosing Diabetic Retinopathy
It's important that anyone who has diabetes gets annual eye exams from an ophthalmologist so diabetic retinopathy can be detected early. When you visit an ophthalmologist, he or she will question you about your medical history and vision and will ask you to read an eye chart. The doctor will then directly examine your retina using an instrument called an ophthalmoscope.
Some of the features of diabetic retinopathy cannot be seen during a basic eye exam and require special exams. To get a better look at the inside of the eye, your doctor might administer drops to dilate your pupils and will then view the retina with lenses and a special light called a slit lamp. A test called fluorescein angiography can reveal changes in the structure and function of the retinal blood vessels. For this test, the doctor injects a fluorescent yellow dye into one of your veins and then photographs your retina as the dye outlines the blood vessels.
Treatment for Diabetic Retinopathy
Treatment for diabetic retinopathy should involve both a medical doctor and an ophthalmologist. Your medical doctor can help you better control blood sugar and can treat other complications of diabetes that may worsen diabetic retinopathy, such as impaired kidney or heart function. Your ophthalmologist can directly treat retinopathy with a laser or a surgical procedure called vitrectomy, to prevent further vascular changes and preserve vision. Don't be surprised if your doctor recommends one of these treatments before you notice any vision problems: Before problems start is usually the best time for treatment.
Laser treatment for diabetic retinopathy, called laser photocoagulation, works in part by creating tiny, painless retinal burns that seal off leaking vessels and reduce swelling. The number of burns the doctor makes and the number of treatments you need depend on the type and extent of your retinopathy and how well it responds to treatment. You may have to wait several months to find out if this treatment is improving your condition.
Your doctor may recommend vitrectomy surgery if you have a hemorrhage that doesn't clear, if you have retinal detachment, or if laser treatment doesn't sufficiently halt the growth of new vessels. During vitrectomy, your doctor drains the gel-like substance inside the eye, allowing her to clear any lingering blood and to remove scar tissue. The vitreous fluid is then replaced with a substitute fluid.
Rare complications of treatment may include blurred vision, headache, glaucoma, difficulty seeing in the dark, decreased peripheral and color vision, and bleeding. In most cases when treatment is recommended, the benefits outweigh the risks.
Although both of these treatments can be very effective, your expectations for either treatment should be realistic. Typically laser or surgical treatment will not restore lost vision; however, treatment can prevent any additional loss of eyesight. If you already have vision loss, your doctor can counsel you about options for visual rehabilitation.
Prevention of Diabetic Retinopathy
Diabetic retinopathy can be minimized with a combination of strict blood sugar control and routine screening with eye exams -- though even with optimal medical care, it is not always possible to prevent or slow retinal damage.
Studies have shown that maintaining near-normal blood sugar can decrease the chance of developing retinopathy and can help keep existing retinopathy from getting worse. Your doctor can provide you with guidelines that may include insulin and other medications, dietary modifications, and exercise. Intensive insulin therapy, which may include frequent blood sugar testing and the use of an insulin pump, may be an option. It's not always easy to stick to the disciplined lifestyle necessary to control your blood sugar; don't hesitate to tell your doctor if you need extra support to adhere to his guidelines.
Routine screening offers the best hope for early detection of diabetic retinopathy. People with type 1 diabetes should have a complete eye exam within five years of diagnosis; those with type 2 should have an eye exam at the time their diabetes is diagnosed. After these initial exams, all people with diabetes should have an eye exam at least once a year. Your doctor may recommend more frequent screenings depending on the severity of retinal damage and on other diabetes complications you have.
Pregnancy can precipitate or worsen retinopathy in women with diabetes who take insulin, so any such woman considering pregnancy should discuss the risks with her doctor. Your doctor will usually recommend an eye exam before pregnancy, a second exam during the first trimester, and additional exams at intervals based on the status of your retinopathy. Women who suddenly develop diabetes during a pregnancy (gestational diabetes) are not at risk of developing retinopathy during the pregnancy.
High blood pressure, high blood cholesterol, and obesity can all promote diabetic retinopathy and should be treated. Smoking is also a culprit: Consult with your doctor about methods for quitting. Never ignore the symptoms of infection, which can worsen diabetic retinopathy. Cataract surgery can affect existing retinopathy, too, so discuss the timing of treatments for retinopathy and cataracts with your doctor.
Researchers continue to investigate new drugs that may prevent or slow diabetic retinopathy; your doctor can provide information about the latest medications approved for these purposes. Depending on the severity of your diabetes and related complications, you may also want to discuss the options of pancreas and kidney transplants, which may protect against retinopathy.
Call Your Doctor About Diabetic Retinopathy If:
- You or your child has been diagnosed with diabetes and you have not discussed retinopathy and routine eye exams with your doctor.
- You experience either gradual or sudden loss of vision.
- You have diabetes and are considering pregnancy.
- You are having trouble sticking to your doctor's recommendations for controlling blood sugar.
- You have vision loss and would like to discuss options for improving your vision.