A cure for blindness that takes just 15 minutes to administer is expected to enter the clinical trial testing stage soon.
Researchers at the University of Berkeley say they have developed an effective method for inserting genes into eye cells that then restore sight to patients suffering from diseases like retinitis pigmentosa and macular degeneration, an illness that mainly affects the elderly.
For the past six years, teams have treated these diseases by injecting a gene virus directly into the retina, but the procedure is invasive and the virus cannot reach all the cells that needed to be targeted.
David Schaffer, of the Berkeley Stem Cell Centre, said: "Sticking a needle through the retina and injecting the engineered virus behind the retina is a risky surgical procedure.
"But doctors have no choice, because none of the gene delivery viruses can travel all the way through the back of the eye to reach the photoreceptors - the light sensitive cells that need the therapeutic gene.
"Building upon 14 years of research, we have now created a virus that you just inject into the liquid vitreous humour 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. It's a 15-minute procedure, and you can likely go home that day."
The team is working with physicians to assess which patients will benefit most.
Over the last 14 years, Schaffer generated around 100 million variants of the treatment. The team then selected the five that were most effective in penetrating the retina.
The best of these were tested on mice, targeting two inherited diseases that cause blindness - X-linked retinoschisis, which only affects boys and makes their retinas look like Swiss cheese, and Leber's congenital amaurosis, which appears at birth and affects 1 in 80,000 people.
In both cases, the treatment delivered the virus to all areas of the retina and restored the cells to near normal.
Schaffer believes the viruses can be used to restore function to faulty genes and also halt processes that kill retina cells: "When I first got here 14 years ago, I really had the idea or the goal that I wanted to work on problems that would have direct impact on human health, and we are now getting there," he said.