Millions of Americans at Risk for Diabetic Retinopathy

If you have diabetes, you face a serious threat to your eyesight that demands careful monitoring.

Fully half of America's 16 million people afflicted with diabetes over a 20-year period will suffer a potentially blinding complication called "diabetic retinopathy," warns Dennis Han, MD, a Professor of Ophthalmology at the Medical College of Wisconsin, who provides care at the Medical College's Eye Institute.

"Diabetic retinopathy" refers to damage to the blood vessels at the back of the eye, causing them to leak or even burst. (The retina is the lining at the back of the eye, and it functions "like the film in a camera," capturing images and sending messages to the brain, explains Dr. Han.)

Diabetes can pose a direct threat to the retina. "Fluctuating levels of glucose, or blood sugar, harm the cells that line the capillaries of the eye. Over time, these vessels close off or become incompetent in playing their proper role in clear vision," Dr. Han says.

The damaged blood vessels can result in retinopathy, with retinal swelling and a loss of "central vision - the ability to read, recognize faces, and drive," the ophthalmologist says. "We see abnormal blood vessel growth, bleeding, scarring and sometimes retinal detachment."

No Early Symptoms, So Exams Vital
What is particularly worrisome for patients and doctors alike is that the very earliest stages of retinopathy set off no alarm bells. "The earliest manifestations cause no symptoms at all, and yet blindness can ultimately result," cautions Dr. Han. At a slightly later stage, leaking blood can lead to blurring or clouded vision, a clear warning sign that something is wrong.

"The lack of symptoms early on is why the routine, periodic eye exam is so important for people with diabetes," stresses Dr. Han. "It's also important for the patient to indicate to the eye doctor that they have diabetes."

One key warning sign, says Dr. Han, is the occurrence of new "floaters," or dark spots that occasionally seem to float across one's vision. "Everyone has floaters, but if these start to occur more frequently, your eyes should be checked out."

Preventive Steps Effective
Preventing retinopathy is far preferable to fighting it once it has taken hold, the eye specialist states. "Once vision loss has developed, it's hard to reverse. But preventive measures can be done very effectively before the patient is at significant risk for vision loss."

These preventive steps include:

• Maintaining good control over blood sugar. "The single most potent step is controlling blood sugar, to lower the hemoglobin level to normal levels of 7 or under. This can reduce the likelihood of diabetic retinopathy by about 80%," Dr. Han says. "This is statistically proven to have a powerful effect, and it is more beneficial early in the course of diabetes."
  Hemoglobin is a protein that carries oxygen and glucose to through the blood to nourish cells. Hemoglobin levels are tested via blood samples, which determine what is called the "A1C" level of hemoglobin, giving an overview of glucose levels for the past three months.
  But patients can conduct "spot" glucose checks with widely-available home testing devices. "These spot glucose tests are an important measure to achieve control over blood sugar, along with medication." Patients using these tests should maintain a written log of the results.
• Getting a yearly eye exam, whether you notice any problems or not. The eye exam should include checking for glaucoma and cataracts, which are also often diabetes-related complications.
• Following your doctor's recommendations regarding your general health. This includes a doctor-approved program of regular exercise, avoiding a sedentary lifestyle, and eating a balanced diet. "The increasing obesity rate is putting greater numbers of people at risk of diabetes and diabetic retinopathy," Dr. Han notes.
• Controlling your blood pressure level.
• Avoiding smoking.
• Having your doctor monitor the level of blood cholesterol and lipids (fats that are not water-soluble) in your system, and following your doctor's instructions to address these factors.

Course of Disease Might Vary
For patients with different varieties of diabetes, retinopathy can take somewhat different courses.

According to the American Diabetes Association, Type 1 Diabetes results from the body's failure to produce insulin, the hormone that allows glucose to enter cells and create fuel for the body. This is sometimes referred to as "juvenile diabetes," a term that has become less accurate as an increasing number of children are now developing Type 2 diabetes. It is estimated that 5% to 10% of Americans who are diagnosed with diabetes have Type 1.

People with Type 1 diabetes that is discovered relatively early in life might not develop retinopathy for a number of years because doctors are consistently checking them for adverse signs. These periodic checks are very important in averting retinopathy.

Type 2 Diabetes results from insulin resistance (a condition in which the body fails to properly use insulin), combined with relative insulin deficiency. Approximately 90% to 95% of Americans (about 17 million) who are diagnosed with diabetes have Type 2. Fueled primarily by obesity, the number of Americans diagnosed with Type 2 diabetes is fast becoming what many in the medical profession consider an epidemic.

For Type 2 diabetics who develop the disease later in life, "the risk of retinopathy may be present even at the time of the first diagnosis of diabetes," Dr. Han says. "So the eyes need to be monitored immediately, followed up by checkups at least annually."

Treatments Available, But Prevention Better
Early detection greatly enhances the chances for successful treatment of retinopathy, Dr. Han emphasizes. At this point, there are two main modes of treatment: laser surgery on the blood vessels and a form of surgery called "vitrectomy."

Laser surgery involves sealing the leaking blood vessels at the back of the eye, so that they stop bleeding into the eye.

Vitrectomy is less common and is often required for patients who have a large amount of blood built up in the fluid portion of the eye, known as the "vitreous." The operation involves replacing the blood-infiltrated vitreous with fresh new fluid that includes a salt solution. "This is used when there is severe bleeding in the eye, and it is more invasive and carries more risk," Dr. Han says.

There are some additional new treatments being tested to stop the growth of abnormal blood vessels that signify retinopathy, reports Dr. Han.

But instead of trying to repair damage, specialists like Dr. Han would much rather work on educating and encouraging patients to take preventive steps to head off retinopathy. "When diabetic retinopathy becomes severe," he says, "it's hard to reverse."

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.