Researchers have found that eye injections of a medication, in combination with laser treatment, result in better vision than laser treatment alone for diabetes-associated swelling of the retina.

In diabetic macular edema, leaky blood vessels in the eye cause swelling—shown within the ring of yellow molecules—that can ultimately lead to vision loss. Image courtesy of NEI.

Diabetic retinopathy is the most common cause of vision loss in working-age Americans. This condition damages the small blood vessels in the eye's light-sensitive retinal tissue. If these damaged blood vessels begin to leak near the center of the retina, known as the macula, the surrounding area swells and causes a condition called macular edema. The macula provides detailed central vision needed for activities such as reading, driving and distinguishing faces. Macular edema can lead to vision loss if left untreated.

Laser treatment of the retina has been the standard care for diabetic macular edema since a 1985 study supported by NIH’s National Eye Institute (NEI) proved its effectiveness. Some small studies have since found benefits in medications that block a chemical signal called vascular endothelial growth factor (VEGF), which stimulates blood vessel growth. Repeated eye injections of anti-VEGF medications, such as ranibizumab (Lucentis), may prevent blood vessels from leaking fluid and causing macular edema.

The new study involved 52 clinical sites within the Diabetic Retinopathy Clinical Research Network (DRCR.net), which is supported by NEI and NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The study included a total of 854 eyes of 691 people. Participants, who were on average in their early 60s, were diagnosed with type 1 or type 2 diabetes and macular edema. They were randomly assigned to 4 study groups: sham injections plus prompt laser treatment within a week; ranibizumab injections plus prompt laser treatment; ranibizumab plus deferred laser treatment after 6 months or more; or injections of a corticosteroid medication known as triamcinolone (Trivaris) plus prompt laser treatment.

Ranibizumab injections could be given as often as every 4 weeks, and triamcinolone injections or laser treatments up to every 16 weeks. Treatment was continued until vision or retinal thickness returned to normal, or if additional treatment didn’t improve vision or retinal swelling. The results appeared online on April 28, 2010, in Ophthalmology.

The researchers found that nearly half the eyes receiving ranibizumab injections, with either prompt or deferred laser treatment, experienced substantial visual improvement after a year. In contrast, only about 30% of eyes that received laser treatment alone or triamcinolone plus laser showed significant improvement.

Participants in all 3 injection groups had a greater decrease in retinal thickness after a year than those receiving laser treatment alone. However, triamcinolone injections brought greater complication rates, including high eye pressure and cataracts that required treatment.

"This comparative-effectiveness study demonstrated that a new treatment can protect and, in many cases, improve the vision of people with diabetic macular edema," says NEI Director Dr. Paul A. Sieving.

DRCR.net researchers will continue to monitor the study participants for at least 3 years to gather more data about the safety and effectiveness of the treatments.