WASHINGTON - US researchers said Wednesday they had developed an easy and effective method for inserting genes into eye cells to help patients with blinding diseases restore sight.

Unlike current treatments, the new procedure, which takes only 15-minutes, is surgically non-invasive, and it delivers normal genes to difficult-to-reach cells throughout the entire retina.

"Building upon 14 years of research, we have now created a virus that you just inject into the liquid vitreous humor inside the eye and it delivers genes to a very difficult-to-reach population of delicate cells in a way that is surgically non- invasive and safe," David Schaffer, director of the Berkeley Stem Cell Center at the University of California, Berkeley and the study's lead author, said in a statement.

"It's a 15-minute procedure, and you can likely go home that day," Schaffer said.

In a study published in the journal Science Translational Medicine, Schaffer and his team generated millions of variants of adeno-associated viruses (AAV), a common but harmless virus that can evolve to infect a wide variety of host cells.

They then used the best of those effective in penetrating the retina known as 7m8 to transport genes to cure two human degenerative eye diseases in rodent models. In each case, when injected into the vitreous humor, the AAV delivered the corrective gene to all areas of the retina and restored retinal cells nearly to normal.

The engineered virus can also penetrate photoreceptor cells in the eyes of monkeys, which are like those of humans, they said.

Schaffer predicted that the virus can be used not only to insert genes that restore function to non-working genes, but can knock out genes or halt processes that are actively killing retina cells, which may be the case in age-related macular degeneration.

Schaffer said they are now collaborating with doctors to identify the patients most likely to benefit from this gene- delivery technique and, after some preclinical development, hope soon to head into clinical trials.