In an extraordinary milestone procedure, scientists in the UK have performed the first gene therapy operation aimed at stopping progression of the most common cause of vision loss. The success of the procedure is yet to be determined, however the scientists suggest this one-off operation could be performed early in the degeneration process and essentially halt the disease in its tracks.

Age-related macular degeneration (AMD) is the most common cause of vision loss in people over the age of 50, and affects millions of people worldwide. The common degenerative disease begins with disruptions in a person's central field of vision, and while it doesn't always result in complete vision loss, it can profoundly alter one's ability to undertake simple things such as reading or even recognizing faces.

In AMD, retinal cells are progressively destroyed by an aggressive immune response. This immune response has been found to be triggered by an overactive protein system. The experimental therapy is designed to deliver a gene that codes for a protein that essentially deactivates this aggressive immune response, and to do this the treatment utilizes a benign virus to transport the new gene to where it needs to go.

'We're harnessing the power of the virus, a naturally occurring organism, to deliver the DNA into the patient's cells," says Robert MacLaren, an ophthalmologist from the University of Oxford working on the project. "When the virus opens up inside the retinal cell it releases the DNA of the gene we have cloned, and the cell starts making a protein that we think can modify the disease, correcting the imbalance of the inflammation caused by the complement system."

The therapy involves surgically detaching the retina and directly delivering the viral solution to the back of the eye. This targeted approach ensures the treatment is contained to a single point, while the virus is also engineered to only infect specific retinal cells.

The first patient to undergo this procedure was 80-year-old Janet Osborne, an Oxford resident with a reasonably advanced case of AMD. The therapy does not reverse any damage already done by the disease, but instead hopes to rapidly halt the degenerative progression. Osborne says her involvement in the experiment was motivated by help others in the future with AMD through establishing the safety and efficacy of the procedure.

"I wasn't thinking of me," says Osborne. "I was thinking of other people. For me, I hope my sight doesn't get any worse. That would be fantastic. It means I wouldn't be such a nuisance to my family."

It may be several years before the therapy is rolled out into clinical use. Further trials are needed to verify how safe the treatment is, and it will take some time before it is clearly proven to be effective. However, the scientists behind this incredible innovation are hopeful this one-off gene therapy procedure could be administered at the early stages of AMD, stopping the disease before it begins to permanently damage the eye, and potentially saving the sight of millions of people around the world.

"This is a rapidly evolving field," suggests MacLaren. "Given that we understand a lot more now about the manufacture of the treatment, and the effects of the virus when doing gene therapy at the back of the eye, as well as all the other gene therapy programmes being developed at the moment, I would hope that we'll see a treatment for people with dry AMD within the next few years."