Doctors have used gene therapy to treat the most common underlying cause of blindness, in a world first, according to Gizmodo.

Age-related macular degeneration (AMD), which causes more sight impairment globally than any other underlying condition, could affect as many as 88 million Americans by 2050, according to the Centers for Disease Control. While it’s too early to tell if the procedure was successful, the experimental surgery represents a step toward a revolutionary treatment for a common and debilitating condition.

Janet Osborne, an 80-year-old woman with AMD affecting both eyes, suffers from sight impairment that makes daily tasks difficult. Her impairment stems from the “dry” type of AMD, also called atrophic AMD, which is tougher to treat than neovascular or “wet” AMD. In her condition, cells in the retina, that are crucial for central vision and focusing, die off and aren’t replenished.

In the procedure, surgeons injected a harmless synthetic virus, containing a modified DNA sequence, into the area. If successful, the DNA would repair the genetic defect itself and stop additional cells from dying. It was performed at Oxford Eye Hospital by University of Oxford ophthalmology professor Robert MacLaren.

Once inside the retinal cell, according to MacLaren, the virus deposits synthetic DNA 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 complement system is composed of proteins that are part of the immune system, but in AMD, it becomes overactive and attacks the retinal cells themselves.

The new procedure aims to shut down the complement system, “but at a very specific point at the back of the eye, so the patient would otherwise be unaffected by it, and we hope that in future it will slow down the progression of macular degeneration,” said MacLaren.

If used early on, the procedure could preserve vision in patients that would otherwise become increasingly impaired over time. In this case, the procedure is experimental and is being performed in patients who have already lost some vision, in order to test its safety. Osborne is one of ten patients participating in the trial.

She hopes the procedure can help her maintain her current level of independence, and continue to garden with her husband.

“I wasn’t thinking of me. I was thinking of other people,” Osborne said in a press release from Oxford. “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.”

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