THURSDAY, May 1 (HealthDay News) -- Injections of the drug ranibizumab can improve vision and reduce macular swelling caused by blockages in the retinal vein in people with macular edema, according to researchers at the Johns Hopkins Wilmer Eye Institute.

"Some patients stabilize after only a few injections, and some require several injections, but the results are very encouraging," Dr. Peter A. Campochiaro, a professor of ophthalmology and neuroscience, said in a prepared statement.

The study included 20 patients with macular edema due to central retinal vein occlusion and 20 patients with macular edema due to branch retinal vein occlusion. They were randomly selected to receive three monthly injections of ranibizumab. One month after the third injection, the average improvement was a doubling of the visual angle.

"This was a substantial improvement. Higher doses led to faster recovery that lasted somewhat longer, but had no effect on improving vision," Campochiaro said.

It's long been suspected that the protein vascular endothelial growth factor (VEGF) plays a role in blood vessel leakage and macular edema. Since ranibizumab binds VEGF, the results of this study suggest that VEGF is a major contributor to retinal vein occlusion-induced macular edema, Campochiaro said.

The results of the three-month endpoint of the study were published in the April issue of Molecular Therapy. Information about continued treatment and follow-up of patients was expected to presented Thursday at the Association of Research in Vision and Ophthalmologyannual meeting, in Fort Lauderdale, Fla.

Two phase III trials of ranibizumab are currently under way. Both are funded in part by drug maker Genentech.