Nearly 26 million Americans have been diagnosed with diabetes, and another 79 million have prediabetic conditions that put them at risk. Roughly half of these persons can be expected at some time to develop retinopathy, the leading cause of blindness among American adults.
If you have diabetes long enough, you’re almost certain to experience at least some of the effects, although retinopathy typically takes 10 to 12 years or longer after the onset of diabetes to show up. Because some persons have type 2 diabetes for years without knowing it, though, eye problems may be already present or even in an advanced stage at the time of diagnosis.
You may not notice any symptoms until the disease has become fairly advanced, and once retinopathy has become established, there is no cure and no treatment that can reverse damage to eyes that has already occurred. However, the risk of vision loss can be reduced by 90 percent or more with early detection and careful management.
The best strategies for protecting yourself are things you should be doing anyway for overall good health:
• Keep your blood sugar under control.
• Lower your cholesterol.
• Watch your blood pressure.
• Don’t smoke.
• Get a dilated eye examination from an ophthalmologist at least once a year.
The latter is crucial and often ignored. According to results of the Los Angeles Latino Eye Study, only 35 percent of type 2 diabetics had received an eye examination within the past 12 months.
Control Your Blood Sugar
The major underlying cause is uncontrolled blood sugar which damages the tiny blood vessels in the retina–the light-sensitive lining of the eye that sends images to the brain. Once these vessels are damaged, they become more vulnerable to changes caused by high cholesterol, high blood pressure and smoking.
The disease process typically occurs in four stages:
Mild nonproliferative retinopathy: Tiny blood vessels begin to swell and balloon out because of blockages to blood flow. At this stage, it’s crucial to control cardiovascular risk factors with exercise, diet and cholesterol-lowering and blood pressure lowering medications.
Moderate nonproliferative: Some blood vessels in the retina become blocked, inhibiting normal blood flow. By this time, the damage becomes increasingly difficult to reverse but it can be managed effectively.
Severe nonproliferative: More and more blood vessels become blocked, leaving several areas of the retina without adequate blood flow. In order to get proper nourishment, the retina sends out signals for new blood vessels to grow–a process known as angiogenesis.
Proliferative retinopathy: This is the most severe stage during which time new blood vessels proliferate in the retina. These blood vessels are abnormal and fragile with thin walls that are vulnerable to leaking. When leaking occurs, the result can be severe vision loss or even blindness.
Until this final stage, changes taking place in the eye are unlikely to cause symptoms but can be readily identified by an eye doctor looking into the eye through a dilated pupil. While early action is best, identification at any time is crucial to providing sight-saving treatment.
Thickening or swelling of the central part of the retina, known as macular edema, can occur at any of the four stages. The macula is needed for sharp, central vision, and damage to it can cause blurring, particularly near the center of the image.
When macular edema is detected, it can be treated with focal laser treatment. Using a laser, the doctor makes several hundred small burns in the affected area, reducing the leakage of blood vessels.
Even when macular edema is present, however, symptoms may not show up or may not be noticed until the proliferative stage. The specks or spots that appear in the person’s vision are caused by bleeding within the eye. (These are to be distinguished from the transparent “floaters” that are common in many persons with or without diabetes.)
Bleeding inside the eye may come and go, but it must be stopped if vision is to be saved. Treatment involves scatter laser surgery. In an effort to shrink the blood vessels, the doctor delivers one to two thousand small laser burns away from the center of the retina. Because so many burns are required, the doctor may need two sessions.
Medications to stop the growth of new blood vessels have also been found effective during this stage.
When extensive bleeding occurs and clouds the vitreous gel that fills the center of the eye, a vitrectomy may be needed. This is a surgical procedure that involves removing the vitreous gel and replacing it with a salt solution.
While these surgical procedures are effective at halting the disease process, they do not restore any vision that was lost.
Over the last five years, however, significant developments in medical management have occurred, offering hope not only to persons who detect problems early but those already suffering retina damage.
Fenofibrate, a drug used along with lifestyle measures and sometimes other medications to lower cholesterol and triglycerides while improving HDL levels, slowed progression and reduced the need for surgery in subjects with existing retinopathy, according to results of the FIELD (Fenofibrate Intervention and Event Lowering in Diabetes) study.
The ACCORD (Action to Control Cardiovascular Risk in Diabetes) study likewise found that fenofibrate combined with simvastatin resulted in a 40 percent reduced risk of progression of retinopathy symptoms over a four-year period.
The role of blood sugar control was established many years earlier in the Diabetes Control and Complications Trial (DCCT). Subjects who kept their blood glucose as close as possible to normal had later onset, slower progression of retinopathy and reduced need for surgical treatment.
Controlling blood sugar, blood pressure and serum cholesterol is a priority that starts before retina damage starts to show up and continues through all stages of the disease. Patients who make that commitment and also make regular appointments with their eye doctor can avoid the worst consequences of diabetic retinopathy.
REFERENCES:
American Academy of Ophthalmology, “What is diabetic retinopathy?” eyeSmart, 2012.
Will Boggs, M.D., “Longstandintg celiac disease a risk factor for diabetic retinopathy,” Reuters Health September 19, 2012 (Diabetes Care, 2012).
James Brice, “Myopia may protect against diabetic retinopathy,” Medscape Medical News, September 21, 2012 (Clinics in Experimental Ophthalmology September 7, 2012).
Daniel Chalk, Martin Pitt, Bijay Vaidya and Ken Stein, “Can the retinal screening interval be safely increased to 2 years for type 2 diabetic patients without retinopathy?” Diabetes Care, 2012;35(8):1663-1668.
Marilyn Haddrill and Chris A. Knobbe, M.D., “Diabetic retinopathy,” AllAboutVision, updated December, 2011.
Hans-Peter Hammes, et al, “Diabetic retinopathy,” Diabetes, March 2, 2011.
Mayo Clinic Staff, “Diabetic retinopathy,” MayoClinic.com, March 27, 2012.
National Eye Institute, “Facts about diabetic retinopathy,” last updated June, 2012.
NIH Senior Health, “What is diabetic retinopathy?” last reviewed September, 2009.
R.L. Thomas, et al, “Incidence of diabetic retinopathy in people with type 2 diabetes mellitus attending the diabetic retinopathy screening service for Wales,” British Medical Journal, March 2, 2012.
A.D. Wright and P.M. Dodson, “Medical management of diabetes retinopathy,” Eye, 2011;25(7):843-849.
Charles C. Wykoff, M.D., Ph.D., and David M. Brown, M.D., “Diabetic retinopathy: a team approach to screening, referral, and treatment,” Medscape Ophthalmology, May 20, 2012.
11/29/2012
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