MONDAY, April 12, 2004 (HealthDayNews) -- As many as four out of every 10 diabetics over 40 in the United States have some form of the potentially devastating eye disorder called diabetic retinopathy, and more than 8 percent of them could face vision loss.
That grim assessment comes from a new collection of estimates, perhaps the most extensive ever released, which also predicts that a third of those diagnosed with type 1 diabetes by age 30 are also at the same risk.
The good news is that doctors can usually treat the disease effectively if it's caught in its beginning stages, and an annual eye exam is the place to start, experts said.
"The problem is that in that early phase, you don't know that anything is wrong. You see fine," said Dr. Frederick Ferris, a clinical director at the National Institutes of Health. "Unless you have regular eye exams, you will miss the best time to intervene. That's the big tragedy."
Diabetes prevents the body from properly processing sugar, also known as glucose. If diabetes is not properly treated, high blood sugar levels can wreak havoc in various parts of the body.
In the eye, blood vessels can begin leaking under the strain. In response, the body creates new, fragile replacement vessels that can themselves bleed, in addition to growing into the wrong parts of the eye, explained Dr. John Kempen, an assistant professor of ophthalmology and epidemiology at Johns Hopkins University. Over time, the retina can lose its ability to function, leading to vision problems or, in some cases, blindness.
"Patients often don't notice they have a problem until they suddenly lose their vision," Kempen said.
He and his colleagues from the Eye Disease Prevalence Research Group, an initiative sponsored by the National Eye Institute and Prevent Blindness America, examined several health studies and used the statistics to estimate the prevalence of diabetic retinopathy in the United States. Their findings appear in the April edition of the Archives of Ophthalmology, which is a themed issue on blindness.
Out of 10.2 million U.S. adults over 40 with diabetes, 40.3 percent have diabetic retinopathy.
The risk is not the same for all races: 42 percent of those who are white have diabetic retinopathy; the estimates are 29 percent and 42 percent for blacks and Latinos, respectively. An estimated 8 percent to 10 percent of diabetics in all three ethnic groups face potential vision loss from the most serious form of the disease.
Among the estimated 889,000 adult Americans who were diagnosed with type 1 diabetes before age 30, diabetic retinopathy threatens the vision of an estimated 32 percent and 30 percent for whites and blacks, respectively.
In some cases, people with type 1 diabetes should get annual eye exams that could help them reduce the risk of vision loss by 90 percent, Kempen said. Annual examinations are even more important for people with the much more common type 2 diabetes, which generally appears later in life, he added.
Overall medical checkups might not pick up the condition, he cautioned: "Without special examination techniques, a general practitioner would have trouble making the diagnosis," he said.
Ferris said only about two-thirds of diabetics visit eye doctors regularly. "We're doing better, and we've been working on getting the message out, but it's still not out," he said.
Even if they don't go to the eye doctor regularly to get their pupils dilated and their retinas examined, diabetics can still help prevent harm to their vision. In addition to annual doctor's visits, "the best things that you can do are control your blood sugar, control hypertension (high blood pressure) if you have it, and control your cholesterol," Kempen said.
In the same issue of the journal, scientists from Johns Hopkins and the Eye Diseases Prevalence Research Group report the following findings:
- The leading causes of blindness differ between blacks and whites: for the former, it's cataracts and glaucoma, and for the latter, it's age-related macular degeneration.
- The prevalence of age-related macular degeneration (AMD) and cataracts is expected to increase in the coming decades, mostly the result of aging baby boomers. For AMD, the numbers are predicted to increase from 1.75 million people to almost 3 million people by the year 2020.
- About a third of Americans over the age of 40 have blurry vision.