Diabetic Retinopathy: a Formidable Challenge
FLEMMING ORSNKOV, MD, MPH, CYNTHIA HOGAN
Of all the ocular complications of diabetes, retinopathy stands out as a severe and relentless opponent. Refinements in treatment options and 40 years of research have greatly reduced the risk of blindness from the disease. Nevertheless, diabetic retinopathy is still a leading cause of legal blindness in U.S. adults between the ages of 20 and 74 and the leading cause of blindness among adults in the developing world.
The Wisconsin Epidemiologic Study of Diabetic Retinopathy found that within two decades of the onset of diabetes, nearly all patients with type 1 diabetes and more than 60% of patients with type 2 develop retinopathy. And in April of this year, the Eye Diseases Prevalence Research Group estimated that 4.1 million U.S. adults over age 40 have diabetic retinopathy, and that 899,000 have vision-threatening retinopathy. Moreover, the prevalence of diabetic retinopathy was shown to increase with age: from 1.4% in people ages 40 to 49, to 3.8% among the 50 to 64 age group, to 5.8% in people ages 65 to 74.
Today, with type 2 diabetes reaching epidemic proportions worldwide, we can expect to see a dramatic increase in the number of people developing diabetic retinopathy. The current statistics on diabetes are almost as difficult to grapple with as the disease itself. According to the American Diabetes Association, 18.2 million people in the United States, or 6.3% of the population, have diabetes. An estimated 13 million have been diagnosed, but nearly a third, or 5.2 million people, have diabetes and don't even know it.
The disease is on the rise among men and women of all ages, races and levels of education. Sedentary lifestyles and poor diet exacerbate the problem. Last year, research by Mokdad et al. noted that the number of people diagnosed with diabetes increased by 61% between 1990 and 2001.
FIGHTING DIABETES IS ONE STEP
It is certainly possible to control hyperglycemia and hypertension. Research initiatives, such as the U.K. Prospective Diabetes Study and the Diabetes Control and Complications Trial, underscore the value and importance of tighter glycemic and blood-pressure control in reducing the overall risk of complications from diabetes.
Novartis has made contributions in this arena. It currently markets nateglinide (Starlix), an oral insulin secretion agent that normalizes mealtime glucose spikes. And LAF237, a novel oral compound in a new class of anti-diabetes agents known as DPP-4 inhibitors, has recently moved into Phase III trials.
But fighting diabetes is only part of the battle. While improved diabetes care can lengthen life expectancy, extending survival also increases the amount of time that individuals are at risk for diabetic retinopathy.
Fortunately, there are promising new noninvasive diagnostic methods, such as optical coherence tomography and functional magnetic resonance imaging, which can provide more accurate information and a deeper understanding of diabetic retinopathy. Growth factor inhibition also shows potential: Blocking VEGF and IGF-1 could prevent the neovascularization that characterizes proliferative disease.
WHERE DO WE START?
Our task will get harder before it gets any easier. Projections suggest that diabetic retinopathy will only continue to increase as a public health problem due to the aging of the population as well as the rise in age-specific prevalence of diabetes.
The impact of diabetic retinopathy -- on the patient's quality of life, on the medical infrastructure, on society -- is already a significant burden, and highlights the need for policy efforts to improve prevention programs. More work is needed to provide physicians with the resources they need. More of an effort must be made to educate diabetic and even pre-diabetic patients about the importance of early detection and management.
The rise in the number of diabetic retinopathy cases, as well as the limited therapy options available, will mandate an increase in research to identify additional treatments that can check the relentless progression of this devastating disease.
Flemming Orsnkov, MD, MPH, is the president of Novartis' Ophthalmics Business Unit. Cynthia Hogan is Novartis' senior vice president/head of Ophthalmics North America.
Editor's Note: Diabetic retinopathy will be the focus of the next issue of Retinal Physician. The issue will be published in October.