Controlling blood glucose levels with intensive insulin therapy can reduce risk of diabetic retinopathy up to 76%.

Many of the chronic, or long-term, complications of type 1 and type 2 diabetes are directly related to elevated blood glucose levels. Long-term diabetes complications include microvascular disease (abnormalities of small blood vessels); neuropathy (nerve damage); changes to the eyes (diabetic retinopathy), skin, gums, and teeth; and macrovascular disease (abnormalities of large blood vessels).

The complications typically appear only after years or decades of having the diabetes, and their development is not inevitable. Strong evidence exists that good control of blood glucose and other risk factors, such as high blood pressure, can prevent or delay the onset of long-term diabetes complications and may reduce their severity if they occur. However, improved glucose control may not reverse these complications once they appear.

Diabetic retinopathy, which affects more than 4.1 million Americans age 40 and older, is the most common eye complication of diabetes. Almost all people with type 1 diabetes and more than 70% with type 2 disease eventually develop diabetic retinopathy, in most cases without experiencing any vision loss. Diabetic retinopathy is characterized by damage to the retina, the light sensitive nerve tissue at the back of the eye that transmits visual images to the brain. This damage is caused by changes in the tiny blood vessels that supply the retina.

In its early stages -- called nonproliferative retinopathy -- the retinal blood vessels weaken and develop bulges that may leak blood or fluid into the surrounding tissue. Vision is rarely affected during this stage. Later on, however, patients can develop proliferative retinopathy. At this stage, fragile, new blood vessels begin to grow on the retina and into the vitreous humor (the gel-like substance inside the back of the eye). These abnormal blood vessels are prone to rupture and bleed into the vitreous humor, causing blurred vision or temporary blindness. Scar tissue resulting from the bleeding can pull the retina away from the back of the eye (a condition called retinal detachment) and lead to permanent vision loss.

At any stage of diabetic retinopathy, severe blurring of vision may occur if fluid accumulates around the macula, the most sensitive portion of the retina that is crucial for seeing fine detail. This condition is called macular edema. If detected early, both macular edema and proliferative retinopathy can be treated with a procedure called laser photocoagulation. Prompt treatment can also spare vision following a retinal detachment. The most important way to prevent diabetic retinopathy or keep it from getting worse is to maintain blood glucose levels as close to normal as possible.

In the Diabetes Control and Complications Trial (DCCT), people with type 1 diabetes who gave themselves multiple insulin injections each day or used an insulin pump reduced their risk of developing diabetic retinopathy by 76% and lowered their risk of having existing retinopathy progress by 54%, compared with people who followed a less rigorous treatment program.

In addition, the United Kingdom Prospective Diabetes Study found that people with type 2 diabetes who controlled their blood glucose levels with medication were 30% less likely to have retinopathy that required laser treatment than people who relied on diet and exercise alone. An annual dilated eye examination performed by an ophthalmologist also is essential to detect diabetic retinopathy in its early stages and monitor its progression. In addition, lowering blood pressure below 130/80 mm Hg can help prevent the onset and progression of diabetic retinopathy. Some-- but not all-- studies indicate that lowering blood cholesterol levels and quitting smoking may be helpful as well.

Diabetic retinopathy -- “a substantial public health problem”

In a compelling article from the April 2004 issue of Archives of Opthalmology researchers reported that more than 40% of middle-aged and older Americans with diabetes have the potentially vision-threatening eye complication retinopathy. A review of eight diabetic retinopathy studies, a federal health survey, and Census data suggests that diabetic retinopathy affects just over 4 million of the roughly 10 million U.S. adults age 40 and up who have diabetes. Moreover, 1 in every 12 diabetics in this age group may have advanced, vision-threatening retinopathy. The findings reveal a high prevalence of diabetic retinopathy in the United States, yet the study authors say the actual number many be higher because it’s believed that many people with type 2 diabetes are unaware they have the disease. The researchers estimate that by 2020, as many as 7.2 million Americans age 40 and older will have diabetic retinopathy, and 1.6 million may have a vision threatening form. Currently, Hispanic and black adults appear to have higher rates than whites of both milder and advanced retinopathy. Calling diabetic retinopathy a “substantial public health problem,” the researchers conclude that more attention needs to be paid to preventing the development and progression of the eye disease.