U.S. researchers said Monday they have found a new way to restore the eyesight in patients who have a blinding eye disease caused by diabetes.

The key is to block a second blood vessel growth protein, along with one that is already well-known, when it comes to treating and preventing diabetic retinopathy, the most common diabetic eye disease, they reported in the U.S. journal Proceedings of the National Academy of Sciences.

Diabetic retinopathy occurs when the normal blood vessels in the eye are replaced over time with abnormal, fragile blood vessels that leak fluid or bleed into the eye, damaging the light- sensitive retina and causing blindness.

Forty to 45 percent of Americans with diabetes have diabetic retinopathy, according to the U.S. National Eye Institute.

Laser-sealing eye blood vessels can save central vision, but this often sacrifices peripheral and night vision, according to the researchers at the Johns Hopkins University and the University of Maryland.

Several recently developed drugs -- bevacizumab, ranibizumab and aflibercept -- can help treat these blood vessels by blocking the action of VEGF, a so-called growth factor released as part of a chain of signals in response to low oxygen levels, which stimulates the growth of new, often abnormal, blood vessels.

But studies have shown that although these drugs slow progression to proliferative diabetic retinopathy, it does not reliably prevent it, said lead author Akrit Sodhi, an assistant professor of ophthalmology at the Johns Hopkins University School of Medicine.

To find an explanation, levels of VEGF in samples of fluid from the eye taken from healthy people, people with diabetes who did not have diabetic retinopathy and people with diabetic retinopathy of varying severity were tested.