A ground-breaking laser treatment could prevent millions of older people from going blind, experts believe.
The technique helps reverse the effects of age-related macular degeneration - the leading cause of blindness in over 60s in the western world.
Developed by pioneering eye expert Professor John Marshall of King's College London, the laser returns the back of the eye to its youthful state.
Improvements to sight were reported in early proof of concept trials.
AMD affects more than 200,000 people in the UK and attacks the central vision.
It develops when a membrane at the back of the eye becomes clogged with natural waste materials produced by the light-sensitive cells, which clouds vision.
In youthful eyes, enzymes clear away the debris, but as the ageing process sets in this system can fail.
The painless "short pulse" laser works by boosting the release of the enzymes to clean away the waste without damaging the cells that enable us to see.
Early tests proved promising in around 50 people with diabetic eye disease - chosen as a model because the problems develop faster than in AMD.
Professor Marshall now plans more studies in patients already suffering from AMD in one eye with the aim of saving the sight in their better eye for as long as possible.
He said once people have advanced AMD in one eye, studies show the condition usually develops in the second eye in 18 months to three years.
"If you can delay the onset by three, four, six, seven or 10 years, it's proof of the principle," he said.
"What this laser is doing is trying to treat the underlying ageing process, as it were, reset the clock so that you don't have the manifestations of visual loss."
He said the aim was to prevent damage and preserve their sight for the rest of their lives.
Professor Marshall said he hoped the treatment would be available within two to five years and one day people in their 40s who have a family history of AMD could choose to have the treatment as a way of preventing the onset of the condition.
Tom Pey, director of external affairs for Guide Dogs for the Blind, which funded the research, said: "This is potentially a huge breakthrough for millions of people across the world."
A spokeswoman for the Macular Disease Society said: "If it is shown to work it is an extremely exciting development and potentially a real breakthrough.
"It will not sadly be useful in those who have already lost their sight to AMD, but it may have great hope for the future."
There is currently no treatment for the most common form of AMD - known as "dry" AMD - which the new laser technique could prevent.
The more aggressive "wet" form of AMD - where new blood vessels cause bleeding and scarring behind the retina - can be stabilised with drugs.
Barbara McLaughlan of the RNIB said: "The prospect that this research may lead to improvements in early treatment is very exciting news, since this could become the first treatment for dry AMD."