Controlling blood sugar may prevent eye problems in diabetes patients

Lowering lipids and cholesterol can also pay dividends, study finds

Keeping blood sugar close to normal and taking drugs to hold down blood levels of cholesterol and other fats can help people with diabetes avoid the potentially blinding eye disease retinopathy, researchers report.

Until now, it hadn’t been clear whether strict control of blood sugar and fats, or lipids, could still deter retinopathy in patients who had been diabetic for as long as a decade.

“The question was whether the horse was out of the barn for this group,” says study coauthor Emily Chew, an ophthalmologist at the National Eye Institute in Bethesda, Md. It turns out, she says, “that you can reduce the risk of retinopathy in these patients.”

Years of high blood sugar can damage blood vessels in the retina, leading to diabetic retinopathy. This results in the buildup of fluid and other deposits in the eye, which can lead to blindness if not treated.

The new study, published online June 29 in the New England Journal of Medicine, involved patients who had lived with type 2 diabetes for roughly 10 years. The study is actually two parts of a large ongoing trial in the United States and Canada. In both parts, patients had no history of eye disease at the outset. All underwent a standard eye exam at the start of the trial and again after four years.

In one analysis, Chew and her colleagues randomly assigned 2,856 people to undertake either an aggressive effort to lower their blood sugar levels or a standard course of blood sugar control that was less stringent. Those in the group that aggressively reduced blood sugar were 33 percent less likely than the others to have developed retinopathy at the four-year point — 7.3 percent compared with 10.4 percent.

In the other analysis, the researchers randomly assigned 1,593 of the study participants to get the cholesterol-lowering drug simvastatin plus either a placebo or a drug called fenofibrate that lowers lipids such as triglycerides. These patients had higher than normal levels of triglycerides at the start. After four years, those getting the drug combination were 40 percent less likely to develop retinopathy than were those getting only the statin — 6.5 percent versus 10.2 percent.

An intervention to lower blood pressure in some of the volunteers showed no effect on retinopathy development.

The beneficial effects of statins in lowering cardiovascular risk in people with diabetes have been shown in the past, says Amod Gupta, an ophthalmologist at Postgraduate Institute of Medical Education and Research in Chandigarh, India. “This study on progression of retinopathy would provide an additional motivation for diabetic patients to control their lipid levels and prevent sight-threatening retinopathy which, for some diabetics, is just around the corner.”

Diabetic retinopathy is highly treatable with steroid injections to stop swelling, laser surgery to cauterize leaky blood vessels and with other surgery to remove excess fluid from the eye. While these interventions can maintain vision in most patients, none cures the underlying biological process by which retinopathy develops.

Retinopathy often occurs with, or precedes, diabetes-related complications of the kidney, nervous system and blood vessels, says physician Barbara Klein of the University of Wisconsin School of Medicine and Public Health in Madison. Writing in the same NEJM issue, she says the report therefore “has great importance, particularly because of the increasing prevalence of diabetes related to aging of the population and also the increasing prevalence at younger ages, which is likely to be related to obesity.”

Meanwhile, roughly half of diabetes patients don’t get eye exams as often as they should, which is annually, Chew says. “We need to do a better job educating our patients,” she says.

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