Laser surgery better than steroid injections for preserving eyesight in diabetics

September 3, 2008 — Newly published results from a clinical trial show that laser surgery is more effective at preserving eyesight in diabetics and has fewer side effects than steroid injections.

Sometimes newer is not necessarily better.

Over the last 5 years, many ophthalmologists began using intraocular steroid injections instead of laser surgery to treat a condition called diabetic macular edema, an abnormal swelling in the eye that develops in 40 to 45 percent of people with diabetes. They adopted the newer treatment based on results from a few clinical studies that suggested treatment with the steroid, intravitreal triamcinolone, might be helpful.

But newly published results from a clinical trial show that the older laser surgery is more effective at preserving eyesight in these patients and has fewer side effects, said Mary Elizabeth Hartnett, M.D., who served as the University of North Carolina at Chapel Hill’s principal investigator in the study.

“I think the results of this study will change practice,” Hartnett said. “However, we still do not know if laser plus triamcinolone would be better than laser alone.”

The study, which was published recently in the online edition of the journal Ophthalmology, was conducted by the Diabetic Retinopathy Clinical Research Network, which is a multicenter network of investigators funded through the National Eye Institute. It is scheduled for publication in the print version of the journal in September.

Hartnett, a professor of Ophthalmology in the UNC School of Medicine, said the network is currently enrolling patients in additional studies that will test the effectiveness of laser surgery, laser plus triamcinolone, or laser plus a type of drug called an anti-VEGF (vascular endothelial growth factor) agent for the treatment of diabetic macular edema.

In the current study, a total of 693 patients with diabetic macular edema took part at 88 sites across the United States. Each person was randomly assigned to corticosteroid or traditional laser treatment.

Following the treatment, investigators tested each patient to determine whether the procedure had prevented substantial vision loss. Investigators defined substantial vision loss as reading at least two less lines on a standard eye chart two years after entering the study.

In the corticosteroid-treated group, 28 percent experienced substantial vision loss as compared to 19 percent in the laser-treated group. In addition, about one-third of the eyes treated with laser therapy showed substantial improvement in vision. Laser treatment had previously been perceived to prevent further vision loss, but not to improve vision.

The corticosteroid-treated group was also far more likely to experience side effects. In fact, 51 percent of the corticosteroid-treated group had cataract surgery compared to 13 percent of those in the laser-treated group. In addition, almost half of the corticosteroid-treated group had increased eye pressure, which may lead to glaucoma. One-third of this group needed eye drop medications to lower their eye pressure. The laser-treated group had significantly less of a problem with eye pressure, as 8 percent of the group required eye drop medications.

Researchers also found that, while not as effective as the laser treatment, corticosteroid treatment did provide some benefit, raising the possibility that combining the two treatments might provide an even greater benefit.

The study was funded by the National Eye Institute, part of the National Institutes of Health.

Media contact: Tom Hughes, 919-966-6047, tahughes@unch.unc.edu

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