Oxford researchers claim to have carried out the world's first gene therapy operation to halt age-related macular degeneration (AMD), the leading cause of untreatable blindness in the developed world.

Dry AMD is a slow deterioration of the cells of the macula. It affects the central part of a patient's vision with gaps or 'smudges', making everyday activities like reading and recognising faces difficult.

If successful, the treatment could have a beneficial impact of patients' quality of life and their ability to remain independent.

The first person to undergo the procedure was Janet Osborne of Oxford, said MacLaren, who carried out the procedure at the John Radcliffe Hospital in the UK.

Like many people with AMD, Osborne has the condition in both eyes, but it is more advanced in her left eye. As is typical with this condition, the central vision in her left eye has deteriorated and is very hazy, although her peripheral vision is better.

Ideally if successful, gene therapy would only need to be performed once, as the effects are thought to be long-lasting.

A key factor in AMD is the complement system, a system of proteins in our immune system that fights bacteria.

In macular degeneration, these proteins are over-active and start to attack the retinal cells, in a similar way to how they would attack bacteria.

"We have a better understanding now on the relationship between the complement system and the AMD disease which lead us to the discovery that restoring the balance of a hyperactive complement system could be a potential therapeutic approach in dry AMD," said Peter Lachman from the University of Cambridge, UK.

The aim of the therapy is to halt the progress of the condition and preserve what vision patients have remaining.

It is hoped that gene therapy can be used in the future on patients with early AMD and so halt the disease before their vision has started to deteriorate.