diabetes affects eyesight

Sight save Sight save BY MARY BROLLEY

“Eye changes in diabetics can occur quickly. Eyes can be normal one year and severely damaged the next.”

For a growing number of Americans diagnosed with diabetes, a simple hour-long test can help ensure that they not only experience life’s most touching moments, but witness the wonder and beauty of them, too.

Whether it’s seeing the joy on a daughter’s face as she floats down the aisle to take her wedding vows, or the wobbly determination of a baby taking his first steps, this test — a complete dilated eye exam — can make a significant difference in a diabetic’s quality of life.

That’s because diabetes can damage the blood vessels in the eyes, resulting in diabetic retinopathy — a disease that can cause vision loss or even blindness. It occurs when the retina becomes damaged by leaking or obstructed blood vessels.

There are four stages of diabetic retinopathy, ranging from mild nonproliferative retinopathy, where microaneurysms — small areas of balloon-like swelling in the retina’s blood vessels — develop, to proliferative retinopathy, its most advanced stage.

In most cases, there are no symptoms in the early stages of the disease. By the time warning signs appear, the disease may be well under way. The longer you have diabetes, the more likely you are to develop diabetic retinopathy. Further, between 40 to 45 percent of Americans diagnosed with diabetes have some stage of the disease.

“Eye changes (in diabetics) can occur quickly,” says Dr. Tien Wong, an ophthalmologist at The Methodist Hospital. “Eyes can be normal one year and severely damaged the next.”

Fortunately, new drug treatments currently in clinical trials at Methodist and the Cullen Eye Institute at Baylor College of Medicine may decrease the need for laser surgery, now the standard of care for treating the disease.

New treatments are needed because diabetic retinopathy — the most common diabetic eye disease and a leading cause of blindness in American adults — will likely rise as Baby Boomers age and, increasingly, succumb to diabetes. In fact, ophthalmologists expect a 65 percent increase in the disease by 2020.

Increasing Awareness

Diabetic retinopathy is one of five age-related eye diseases that have spurred the launch of an awareness campaign — “EyeSmart”— sponsored by the American Academy of Ophthalmology.

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Dr. Tien Wong

EyeSmart was developed in response to studies indicating that Americans are largely unaware of the risks they face from age-related eye diseases. For example, although the consequences of diabetic retinopathy are severe, few Americans seem concerned about their risk of developing it.

Wong strongly urges newlydiagnosed diabetics of any age to have a complete eye exam promptly, and follow up with their ophthalmologist every year without fail.

The exam should be a dilated exam so that the doctor can establish a baseline picture of the condition of the patient’s eyes and vision. After the baseline exam, the ophthalmologist will be able to advise the frequency of subsequent exams.

Diabetic retinopathy causes two main problems: macular edema, a swelling in the back of the eye; and new blood vessel growth. The latter is the body’s automatic response to the existing damage, spurring the growth of more blood vessels to heal the retina but doing more damage in the process.

In its early stages, diabetic retinopathy may be controlled by monitoring blood sugar, blood pressure and blood cholesterol. But if the disease progresses to proliferative retinopathy, treatment nearly always involves laser surgery.

“Laser treatments are the mainstay — the only proven treatment,” says Dr. Eric Holz, an associate professor of ophthalmology at Baylor College of Medicine.

For macular edema, eye surgeons cauterize the swollen and leaking vessels with a laser to stop them from leaking. For new blood vessel growth, they zap the diseased peripheral retina to save the central retina, which is crucial for reading, driving, etc.

Dr. Eric Holz

“We turn sick retina (on the edges) into dead retina,” Holz says. “This may stop retinal detachments from happening.”

Finding what works best

The new clinical trials test the effectiveness of sustained-release steroids and injections of anti-angiogenic drugs that have been effective in treating macular degeneration. (The studies are in the early stages, so neither physician was able to comment on their progress.)

Because these anti-angiogenic drugs block the growth of new blood vessels, they may be an improvement over lasers.

“Laser treatment is destructive,” Wong says. “If we can minimize the amount (of lasers) used, we can preserve more retina and hence, more vision.”

Data gathered from Wong’s patients is contributing to the Diabetic Retinopathy Clinical Research Network, a national database of research on diabetesinduced retinal disorders. “Our patients are helping us discover what works best,” he says.

Holz says his patients value their sight greatly and are willing to make lifestyle changes and participate in experimental trials to save or keep their vision. “Nothing is as concrete as vision to a patient,” he says. “The impact of my work is very apparent to the patient and the doctor.”

The ultimate goal of the studies, Holz says, is the discovery of a safe and effective drug that can be packaged in a sustained-release capsule for implantation in the eye, providing longer-term protection from the ravages of the disease.

Wong, too, believes these new treatments are a promising option for saving the sight of Americans afflicted with diabetes. “Diabetologists expect an epidemic increase in diabetic retinopathy in years to come,” he says. “This (the clinical trials under way) is exciting stuff. I love being at the cutting edge of retinal treatments.”

To obtain a physician referral, call 713.790.3333 or visit methodisthealth.com.