Diabetic retinopathy is a retinal blood-vessel disease that affects people with diabetes. It may progress from early to advanced disease. At first, vision is unaffected. In later stages, new blood vessels and fibrous tissue grow on the retina, interfering with sight. If not promptly treated, vision loss may occur. Tight control of blood sugar levels may prevent or slow the progress of this disease. Laser surgery may help preserve vision in some people with advanced disease.
Diabetes affects vision
Diabetes affects tiny blood vessels that nourish the retina, the eye’s internal projection screen. Over time, the retinal blood vessels become clogged or leak. When the retina’s blood vessels are unable to deliver enough nutrients to its light-sensitive cells, vision loss occurs. This disease is called diabetic retinopathy.
In the early stages, tiny blood vessels in the retina become blocked or damaged, cutting off the food supply to small patches of light-sensitive cells. Blood (hemorrhage) or fluid (exudate) leaks into retinal tissues, causing swelling. At first, sight is rarely affected. For that reason, this stage is called background retinopathy.
Over time, abnormal blood vessels grow into the retina and vitreous (jelly-like substance that fills the eye) in places where tiny blood vessels no longer function. These rogue vessels are fragile and rupture easily. When leaks occur, complications can cause severe vision loss if not promptly treated. This advanced stage of disease is called proliferative retinopathy.
When abnormal vessels burst, blood or fluid can collect in the retina’s central spot or macula. This spot is responsible for central vision. When it is swollen, central vision gets blurry. Fine details are lost. Reading, watching television and driving become difficult. If not treated promptly, macular edema may cause permanent vision loss.
As the body works to repair damage to the retina, scars form. Eventually, scar tissue can push the retina away from the back of the eye (retinal detachment). This detachment causes permanent loss of vision. If caught early, laser surgery may prevent or limit irreversible vision loss.
When abnormal vessels bleed into the vitreous, vision is blurred. Specks of blood may float through your field of vision. Large leaks into the vitreous can obscure sight, making it difficult to tell light from dark. The blood may clear away in a few days, months or even years. Large leaks (hemorrhages) often occur during sleep. If a lot of blood builds up in the vitreous, the eye doctor may recommend a vitrectomy. This operation replaces the cloudy vitreous with a clear solution.
Timely treatment of problems — macular edema, retinal detachment, abnormal blood vessel formation or blood-clouded vitreous — may prevent or limit permanent loss of vision in people with diabetes.
Little is known about the causes of diabetic retinopathy. One theory suggests that, in diabetes, the retina develops a low oxygen level (hypoxia). It then sends out a chemical distress signal. In response, new but fragile blood vessels grow to feed oxygen to the retina.
Some factors can worsen diabetic retinopathy:
- poor blood-sugar control
- Native, African and Mexican American background
- male gender
- diabetes at an early age
- high blood pressure
- kidney damage
Scientists are studying the abnormal blood vessels that form in diabetic retinopathy to unlock the secrets of this condition.
Treatment of advanced (proliferative) retinopathy depends on your overall health, eye health, eye structure and specific eye problem.
To find out if tiny retinal blood vessels are leaking, the eye doctor may order fluorescein angiography. This test is usually done in a hospital by an eye specialist. A yellow or red dye is injected into the arm. This fluorescein dye travels rapidly through the body. When lit by ultraviolet rays directed into the eye, the dye glows yellow-green, allowing the eye specialist to capture leaky vessels on film.
Common treatments for proliferative retinopathy are laser surgery and vitrectomy (replacement of bloody vitreous with a clear solution). Neither procedure can reverse vision loss, but timely treatment may prevent further loss of sight.
Laser surgery can prevent severe vision loss in people with diabetes. People with proliferative retinopathy have a 90% chance of keeping their sight if treatment begins before the retina is severely damaged.
To control swelling under the retina’s central spot or macula, short bursts of laser are used to vaporize or seal leaky blood vessels. The surgeon aims directly at damaged vessels. This operation is called focal laser therapy.
When the likelihood of blindness is high, scatter laser therapy is used to control the widespread growth of abnormal blood vessels. Rather than hitting just one spot, the laser beam makes hundreds of tiny burns over the retina’s surface. Some peripheral or side vision is sacrificed to save the remaining vision.
Laser surgery can also seal the retina to the back of the eye, preventing permanent vision loss from retinal detachment. Timely laser surgery can stabilize vision, but it cannot restore lost sight or repair a damaged retina.
What to expect during laser surgery
Laser surgery is usually done in a doctor’s office or eye-care clinic.
Before surgery, the surgeon dilates the pupil and numbs the eye with drops. The person sits in front of the laser. The surgeon directs the beam into the eye through a special lens. People often see bright green or red flashes and feel a stinging sensation during this procedure. The operation takes only a few minutes. Afterward, blurry vision and soreness persist for a day or two. Pain medications control any discomfort. Little recuperation time is needed.
Laser surgery can reduce color and night vision. An eye doctor can explain other complications of laser surgery.
A timely vitrectomy — soon after bloody leakage clouds the vitreous — is more likely to protect sight than waiting for cloudiness to go away on its own. Early vitrectomy is especially important for people with insulin-dependent (Type I) diabetes, who are more likely to go blind after large leaks (hemorrhages) from abnormal blood vessels.
During vitrectomy, the eye surgeon removes bloody vitreous from the eye and replaces it with a clear solution. Light can pass through this clear fluid — restoring normal sight. Since normal vitreous is mostly water, people don’t notice any difference between it and the clear fluid.
Depending on your health and eye structure, this operation may be done in hospital under general anesthesia or in a clinic under local anesthesia. The eye surgeon makes a small cut in the white of the eye. A special instrument sucks out the vitreous, then floods the eye with clear fluid.
Afterward, an eye patch is worn for a few days or weeks. The eye will be red and feel sensitive. The eye doctor prescribes eye drops to ward off infection and advises people to avoid certain activities.
Eye surgeons can treat the problems caused by diabetic retinopathy, but not the condition itself. Only one thing can prevent or delay the complications of diabetic retinopathy: better control of blood sugar levels.
The Diabetes Control and Complications Trial found that people with insulin-dependent (Type I) diabetes who tightly controlled their blood sugar levels had 76% less eye damage from diabetic retinopathy than people who did not.
Unless complications develop, treatment is rarely necessary for background retinopathy.
Diabetic retinopathy is the most common cause of new vision loss in adults from 20 to 74 years of age. It affects half of the 14 million Americans with diabetes. It is the main reason why people with diabetes have a four times greater risk of vision loss than others.
When first diagnosed with non-insulin-dependent (Type II) diabetes, up to 21% of people have signs of diabetic retinopathy. After 15 years of diabetes, 97% of people with insulin-dependent (Type I) diabetes and 80% of people with non-insulin-dependent (Type II) diabetes have signs of the disease.
Because diabetic retinopathy can blind without warning, The National Eye Institute (USA) urges all people with diabetes to have a yearly eye test for diabetic retinopathy. Pregnant women with diabetes should have an eye test in each trimester.
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