Article updated and reviewed by Edward B. Feinberg, MD, MPH, Chair, Department of Ophthalmology, Boston University School of Medicine on May 2, 2005.
Diabetic retinopathy is damage to the blood vessels in the eye caused by diabetes. It is the leading cause of visual loss among American adults aged 20 to 65.
Diabetic retinopathy is caused by diabetes. It affects the retina - the light-sensitive tissue at the back of the eye that transmits visual messages to the brain. . If you think of your eye as a camera, the retina would be the film in the camera. If the retina is damaged, the result will be visual impairment or blindness.
Diabetic retinopathy is broadly classified as non-proliferative diabetic retinopathy and proliferative diabetic retinopathy.
Nonproliferative diabetic retinopathy is characterized by changes in the blood vessels of the retina. The walls of the blood vessels become weaker and more porous. Some small blood vessels called capillaries may become blocked.
Proliferative diabetic retinopathy is characterized by the growth of new and abnormally weak blood vessels from the retina into the vitreous gel that fills the eye.
Early diabetic retinopathy begins with a few blocked small vessels and small bulges of blood vessel walls called microaneurysms. These bulging areas leak excess fluid into the retina which disturbs the retina’s ability to process light images into nerve impulses. The blocked vessels may also deprive parts of the retina of adequate oxygen, and this too contributes to a disturbance in the retina’s ability to process images. This non-proliferative form of retinopathy may cause mild to severe blurring, but does not cause blindness. In many people it never progresses beyond mild changes which cause little or no blurring of vision, while others will develop severe blurred vision. The visual center of the retina is called the macula, and fluid accumulation in the macula is called “macular edema”. When this accumulation of fluid is severe enough to require treatment, your doctor may call it “clinically significant macular edema” (CSME).
Some, but not all, patients with non-proliferative diabetic retinopathy will begin to develop new vessel growth on the surface of the retina and move into the category of proliferative diabetic retinopathy. These fragile new vessels can easily rupture and bleed into the vitreous gel which fills the eye, blocking vision. Both the abnormal vessels and the blood clots from them may form scar tissue. This scar tissue shrinks and may pull on the retina, creating a form of retinal detachment called “traction retinal detachment”. This happens only in a small minority of people with diabetes, but may cause severe vision loss, or even total blindness.
Approximately 40 percent of all people with diabetes have at least mild diabetic retinopathy. About 3 percent suffer severe visual loss because of this disease. In general, the longer one has had diabetes, the greater are one's chances of developing diabetic retinopathy. Diabetic retinopathy generally takes at least eight years to develop in juvenile onset diabetes, but may be present at the time adult onset diabetes is first diagnosed. High blood pressure and high cholesterol in the blood are additional risk factors that your doctor will address.
Patients with diabetes are also at greater risk for other eye diseases such as cataract and glaucoma. Your doctor will include evaluation for these problems in your examination.
Early diabetic retinopathy causes few, if any, symptoms. Characteristic signs of retinal changes may be seen during examination of the retina. Severe retinopathy may develop prior to noticeable vision loss, with late sudden onset of vision loss with hemorrhage or retinal detachment.
Because diabetic retinopathy can begin and get a foothold before it causes symptoms, all patients with diabetes should have an eye examination with pupils dilated at least once a year. Often your doctor will take photographs of your retinas. A dye, called fluorescein, may be injected in the blood stream to show further details of the circulation in the retina. This is called fluorescein angiography.
Proper treatment of diabetic retinopathy can cut the risk of vision loss by over half. Treatment before diabetic retinopathy causes severe loss is much more effective than later in the disease. For this reason, early diagnosis is critical in order to prevent visual loss and blindness.
Laser treatment may prevent visual loss in many people with diabetic macular edema. In this treatment, called photocoagulation, precise beams of light from a laser are aimed at leaking retinal blood vessels near the macula. The goal of treatment is to seal the vessels and prevent further leakage. In many patients, this treatment halts the decline in vision or even reverses it. Injection of steroid medication is an important new treatment that may supplement laser treatment.
Proliferative retinopathy is also treated with a laser. The abnormal vessels may be cauterized directly, but more often the abnormal vessels are near the nerve carrying vision from eye to brain, and cannot be treated directly. In these cases, the part of the retina that gives peripheral vision is heavily treated. This part of the retina secretes a chemical that triggers the new vessel growth and the treatment decreases this chemical and stops the new vessels over half the time.
A few diabetic retinopathy patients - including some who have had photocoagulation - will develop severe bleeding and scarring despite adequate laser treatment. Many patients with this problem can be treated with surgery to remove the blood and scar tissue.
Following vitrectomy, patients can often see well enough to move around on their own. Occasionally, vision in the operated eye recovers enough for the patient to resume reading or driving.
There are ways to prevent or lessen the risk of eye damage caused by diabetes.
The Diabetes Control and Complications Trial proved that careful control of blood glucose levels may prevent the development of diabetic retinopathy.
Regular eye examinations are especially important for children who have had diabetes for 5 years or longer, for adults at the time of diagnosis, for those who have difficulty controlling the level of sugar in their blood, and for diabetic women who are considering becoming pregnant. All of these people are at increased risk for diabetes-related eye problems.
Editorial review provided by VeriMed Healthcare Network.