Diabetic Retinopathy
Diabetic retinopathy is damage to the retina as a result of diabetes.
Diabetes mellitus can produce two types of changes in the eye. These changes, nonproliferative and proliferative retinopathy, are among the leading causes of blindness in the United States and other developed countries. Some retinal change occurs in virtually all people with diabetes, whether or not they use insulin therapy. People with diabetes who also have high blood pressure are at higher risk of developing diabetic retinopathy because both conditions tend to damage the retina.
High levels of sugar (glucose) in the blood make the walls of small blood vessels, including those in the retina, weaker and, therefore, more prone to damage. Damaged retinal blood vessels leak blood and plasma into the retina.
The extent of retinopathy and vision loss is related to how poorly blood sugar levels are controlled and how long a person has had diabetes. In general, retinopathy develops after a person has had diabetes for at least 10 years.
Symptoms and Diagnosis
In nonproliferative retinopathy, small blood vessels in the retina leak. The area around the leak may swell, causing damage to parts of the field of vision. If the leakage is near the macula, central vision may blur. At first, the effects on vision may be minimal, but gradually vision may become impaired. A blue-yellow color vision abnormality may develop, interfering with color perception. Blind spots may occur, although these may not be noticed by the person and are usually discovered only if testing is carried out. Swelling of the macula (macular edema), due to leakage of fluid from blood vessels, can eventually lead to significant loss of vision.
In proliferative retinopathy, damage to the retina stimulates the growth of new blood vessels. The new blood vessels grow abnormally, sometimes leading to hemorrhage or development of scars. Extensive scarring may lead to retinal detachment. Proliferative retinopathy tends to result in greater loss of vision than does nonproliferative retinopathy. It can result in total or near-total blindness due to massive hemorrhage into the vitreous humor (the jellylike substance inside the back part of the eye) or to retinal detachment.
A doctor diagnoses nonproliferative and proliferative retinopathy by examining the retina with an ophthalmoscope or a slit lamp. Fluorescein angiography helps to determine the location of the leaks (see Section 20, Chapter 225).
Prevention and Treatment
The best way to prevent diabetic retinopathy is to control the diabetes and keep blood pressure at normal levels. People with diabetes should have annual eye examinations, so that retinopathy can be detected and any necessary treatment can be started early.
Treatment consists of laser photocoagulation, in which a laser beam is aimed into the eye at the retina to slow the growth of abnormal new retinal blood vessels and decrease leakage. Laser photocoagulation may need to be repeated. If bleeding from damaged vessels has been extensive, a procedure called vitrectomy may be needed. In this procedure, blood is removed from the cavity in which the vitreous humor lies. Vision often improves after vitrectomy for vitreous hemorrhage, and vision may improve after vitrectomy for retinal detachment. Laser treatment only rarely improves vision, but it commonly prevents further deterioration.
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