Researchers say they have successfully restored limited vision in a blind man using a new type of gene therapy, reports Tina Hesman Saey of Science News.

The study, published this week in the journal Nature Medicine, used a gene for light-detecting proteins taken from a type of algae to rebuild nerve cells in the man’s eye, reports Jocelyn Kaiser for Science.

“Seeing for the first time that it did work—even if only in one patient and in one eye—is exciting,” Ehud Isacoff, a neuroscientist at the University of California, Berkeley who was not involved in the study, tells Carl Zimmer of the New York Times.

The man’s restored vision can’t be described as full vision, per the Times, as he requires special goggles and still can’t see colors or pick out faces or letters. But where the 58-year-old man, who suffers from a genetic disease called retinitis pigmentosa, could only barely detect light before the procedure, he can now perceive and count objects—even the white stripes of a crosswalk, according to Science News.

“It’s obviously not the end of the road, but it’s a major milestone,” José-Alain Sahel, an ophthalmologist at the University of Pittsburgh and the Sorbonne in Paris and lead author of the study, tells the Times.

The study presents the first instance of the new technique, called optogenetics, successfully being used to treat a human patient, according to Science.

Retinitis pigmentosa, which impacts more than two million people around the world, causes the light-sensitive cells on the surface of the retina to die, reports James Gallagher for BBC News.

To partially restore the man’s sight with optogenetics, researchers inserted the gene that codes for light-sensitive proteins found in algae and bacteria called opsins into the cells at the back of one of his eyes. Opsins change their shape in response to light and microbes use them to inch toward light, according to BBC News.

With the genetic instructions for making opsins inserted into his eye, the researchers were able to repurpose nerve cells in the eye called ganglion cells, which are not normally involved in detecting light, into new light-receptor cells, per the Times.

These new opsins in the man’s eye send electrical signals to his brain when they are exposed to light and subsequently change shape. The catch is that these opsins only respond to amber colored light, which is why the special goggles were necessary, according to BBC News. The goggles are equipped with a camera on the outside and a small video screen on the inside that beams the patterns of light from the outside world to the man’s eye in amber hues. Additionally, the ganglion nerve cells and their new shapeshifting opsins typically respond to changes in light, so the goggles use pulses of light rather than a continuous video to get them to fire, per Science News.

Getting this system to work also required some seven months of training the volunteer’s brain to recognize and make sense of the new signals it was getting. This practice involved wearing the goggles at home and on walks, according to the Times. Around the seven-month mark, the man, who lives in France, excitedly realized he could see the white stripes of a crosswalk.

In lab tests, he was able to correctly count the number of objects set out on a table before him 12 out of 19 times and was able to recognize things such as a book, cups and a bottle of hand sanitizer, according to Science News. Importantly, the man also told researchers the goggles made daily life a bit easier to navigate. Tasks like locating a phone or a plate or perceiving a piece of furniture or a door became possible, according to Science.

Sahel and his collaborators are now seeking to move their technique through clinical trials, according to the Times. Other companies are also hard at work on developing similar methods.

Botond Roska, a neuroscientist and gene therapist at the Institute of Molecular and Clinical Ophthalmology Basel and the University of Basel in Switzerland and co-author of the study, tells Science News that their technique is not a cure for blindness: “For now, all we can say is that there is one patient … with a functional difference.” Still, Sahel tells Science News he believes this clinical result is “a milestone on the road to even better outcomes.”

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