Man's sight returns after eye cells modified
• A man who lost his sight nearly 40 years ago can see objects again after his eye cells were genetically modified to become sensitive to light.
The 58-year-old had suffered from retinitis pigmentosa, a condition in which the top layer of the retina degenerates so the eye was unable to sense light for most of his adult life.
Nearly 13 years ago, scientists theorized that intact ganglion cells at the bottom of the retina could be repurposed as light-sensitive cells, and take on the role of the damaged top layer.
Now, in a groundbreaking experiment, scientists have genetically modified one eye by inserting genes from light-sensitive algae into the ganglion cells and triggered them using special goggles.
The goggles record the world in real time and convert the image into pulses of red and amber light, which shine into the retina, activating the cells that connect to the optic nerve to restore sight.
The treatment allowed the patient to recognize, count, locate and touch objects for the first time in decades.
“The retina is a biological computer at the back of your eye. It's like a hamburger, the top bread is a photosensitive layer and the bottom bread forms the optic nerve and talks to the rest of our brain. In between, representing the salad, tomato and meat, are the computational layers that compute the visual field,” explained Botond Roska, a professor at the University of Basel, Switzerland.
“In retinitis pigmentosa, the photosensitive layer is damaged but the rest is intact, like a hamburger without the top bread. In optogenetic therapy, we create an artificial photosensitive layer targeting ganglion cells, which are the lower bread. The brain has to learn a new language because the signals from the ganglion cells are not the usual ones.”
British scientists hailed the work, published in the journal Nature Medicine, but said more studies would be needed to find out if it could restore sight to a useful level for many people.
There is no treatment for retinitis pigmentosa except for a gene replacement therapy, which works only on an early-onset form of the disease to prevent further damage.
The scientists believe the patient's eyesight will continue to improve with training. Treatment had to stop last year because of the pandemic and several other patients are currently undergoing the therapy.
“Before the treatment the patient couldn't see anything but spontaneously he was able to see stripes on the street and then was able to detect objects on the table and to grasp the objects, and count the objects,” said Jose-Alain Sahel, a professor at Sorbonne University in Paris.
The researchers believe patients will be keen to have the treatment because the gene insertion technique is simple, and the goggles are not intrusive.