According to researchers at Johns Hopkins' Wilmer Eye Institute, the drug, sold as Lucentis by Genentech, appears to block a protein called vascular endothelial growth factor (VEGF) that promotes the growth of new blood vessels.

Quan Dong Nguyen, who led the Hopkins study, said VEGF is released when the blood supply in the eye is restricted by blood-vessel damage related to diabetes.

The damaged vessels leak fluid and fat into the macula, the part of the retina responsible for seeing fine details. In an attempt to obtain more oxygen, VEGF creates new blood vessels that only add to the problem because they block light from reaching the retina. If the condition is not treated, it leads to diabetic retinopathy and blindness.

The team injected four doses of ranibuzumab over six months into the eyes of 10 patients with diabetes who had already experienced some vision loss. Within a week, several patients experienced dramatic reductions in the thickness of their maculas, and there were further improvements with each injection. By the end of the study, every patient could read at least two more lines on the standard eye chart, and the thickness of their maculas had decreased an average of 85 percent.

A report on the study can be found in the December issue of the American Journal of Ophthalmology.

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