A promising new drug therapy used to treat abnormal swelling in the eye - a condition called diabetic macular edema - proved less effective than traditional laser treatments in a study funded by the National Eye Institute (NEI), part of the National Institutes of Health (NIH).
The study, published online in July in the journal Ophthalmology, demonstrates that laser therapy is not only more effective than corticosteroids in the long term treatment of diabetic macular edema, but also has far fewer side effects.
Between 40 and 45 percent of the 18 million Americans diagnosed with diabetes have vision problems, such as diabetic macular edema. This condition occurs when the center part of the eye's retina called the macula swells - possibly leading to blindness. Ophthalmologists traditionally use lasers to reduce the swelling in areas of the macula. However, starting around five years ago, early reports of success in treating diabetic macular edema with injections of a corticosteroid called triamcinolone led to the rise in popularity of this alternative therapy. This is the first study to compare the long-term benefits of both treatments and evaluate their potential side effects. While triamcinolone was used in this study, there is no scientific rationale at this time that one corticosteroid preparation should be substantially different from another.
"Results of this study should confirm the use of laser treatment for diabetic macular edema and will have a significant impact on quality of life for tens of thousands of people being treated for diabetic macular edema in the United States each year," according to Paul A. Sieving, M.D., Ph.D., director of the NEI. Only diabetic macular edema was examined as part of this study. Macular edema from conditions other than diabetes may respond to corticosteroid treatment and laser treatment differently.
A total of 693 patients with diabetic macular edema participated in the study 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. Improvements in vision were not found in the only prior study evaluating laser treatment for diabetic macular edema because most subjects enrolled in that study already had good to excellent visual acuity and therefore, no room to improve.
"Many of the investigators were surprised by the results," said Dr. Michael Ip, associate professor of ophthalmology at the University of Wisconsin, and chair of this protocol for the Diabetic Retinopathy Clinical Research Network (DRCR.net). "These findings substantiate the importance of laser treatment in the management of diabetic macular edema." The DRCR.net is a collaborative network, supported by the NEI, dedicated to facilitating multicenter clinical research of diabetic retinopathy, diabetic macular edema and associated conditions.
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 found that, while not as effective as the laser treatment, corticosteroid treatment did provide some benefit. "Our findings raise the possibility that combining laser with corticosteroids might produce greater benefit," said Dr. Neil Bressler, chair of the Diabetic Retinopathy Clinical Research Network and professor of ophthalmology at The Johns Hopkins University. The Diabetic Retinopathy Clinical Research Network is conducting a study that is comparing a combination of corticosteroids and laser with laser alone.
For more information on the Diabetic Retinopathy Clinical Research Network visit www.drcr.net.
The National Eye Institute (NEI) is one of the National Institutes of Health (NIH) and is the federal government's lead agency for vision research that leads to sight-saving treatments and plays a key role in reducing visual impairment and blindness.