How bionic eyes can restore vision and help blind people see

As a child, Max Hodak learned to develop film in a darkroom with his late grandfather, who was nearly blind.

Hodak’s grandfather had retinitis pigmentosa, a congenital disease that affects one in five thousand people – more than two million worldwide. Most people with the condition are born with intact vision. Over time, they first lose peripheral vision, then central vision and finally their eyesight, sometimes already in middle age.

“He obviously had a career and was a photographer, and I saw that,” Hodak said of his grandfather, who became an aerospace engineer and briefly worked on heat shields for spacecraft. “But most of my memories as a child were of him being quite profoundly blind.”

However, possible solutions are within reach. Science, a startup company in Alameda, California, has designed a visual prosthesis called the Science Eye that could restore vision, albeit in a limited form, to people with retinitis pigmentosa. Hodak, the CEO, co-founded the startup after a stint at Elon Musk’s company Neuralink. Other companies, such as Paris-based biotechnology company GenSight Biologics and New York’s Bionic Sight, are also experimenting with methods to restore vision.

They all base their work on a research tool in neuroscience called optogenetics, a form of gene therapy that delivers proteins called opsins via injection into the eye to increase the light sensitivity of cells in the retina, the tissue layer at the back of the eyeball . .

Therapeutic optogenetic therapy for vision restoration certainly holds promise, said Anand Swaroop, a senior investigator at the National Eye Institute in Bethesda, Maryland, who has been working on hereditary retinal degeneration for nearly four decades. But there is still room for improvement.

“At least at this stage it seems to be very good in cases where someone is completely blind,” Swaroop said. “You have to be able to find your way in it. You won’t run into things, which is great. But you are not going to distinguish many different characteristics.”

How optogenetics works

During normal vision, light enters the eye through the lens and forms an image on the retina. The retina itself consists of several types of cells, mainly photoreceptors. Photoreceptors are light-sensitive cells in the form of rods and cones that contain opsins. Normally, photoreceptors convert light into electrical signals that travel to the retinal ganglion cells, which in turn send those electrical signals to the brain via the optic nerve. This is how you now read the words on this page.

In retinitis pigmentosa, the rods and cones in the photoreceptors are broken down and eventually die. First, peripheral vision disappears and people develop tunnel vision: they have to turn their entire head to see the world around them. Many people with tunnel vision need a cane to help navigate the world (and to avoid bumping into things, like furniture.) Blindness follows soon after. However, the destruction of the photoreceptors does not affect the brain’s ability to process electrical signals – and, crucially, the ganglion cells remain intact.

Optogenetics attempts to bypass the usual choreography by delivering opsin proteins directly to the ganglion cells, meaning they can be stimulated by light to send signals to the brain.

The Science Eye contains two elements. The first is an implant consisting of a wireless current coil and an ultra-thin, flexible micro-LED array that is applied directly to the retina – a surgery that is more extensive compared to other eye procedures such as cataract repair. According to Hodak, the array – prototypes of which are being tested on rabbits – offers eight times the resolution of an iPhone screen.

The second element is frameless glasses, similar in size and shape to regular prescription glasses, containing miniature infrared cameras and inductive current coils.

Put it all together and the process looks like this:

Step 1

Inject opsins into the ganglion cells of the eye.

Step 2

Install the implant.

Step 3

The glasses activate the modified ganglion cells by wirelessly communicating information from the visual world; in turn, the new light-sensitive ganglion cells transmit that information to the brain via the optic nerve.

The eye no longer receives an image, but digital information. And the results?

“You should be able to walk across town to buy a sandwich without getting hit,” Hodak said.

More research into retinitis pigmentosa

Other companies are already helping to restore vision to people with retinitis pigmentosa.

GenSight Biologics uses an optogenetics-plus-glasses approach to amplify light that genetically edited ganglion cells can decode. According to clinical trial results published in 2021 in the journal Nature Medicine, GenSight’s method could help locate objects on a table. That patient, a 58-year-old man, was diagnosed with retinitis pigmentosa at age 18.

Bionic Sight has firsthand experience with patients who are beginning to distinguish between features. The method involves a gene therapy vector that delivers an opsin called Chronos via injection into their patients’ eyes to increase the light sensitivity of intact ganglion cells. For people with tunnel vision, the injection of opsin seems to be sufficient.

For patients with poorer vision, Bionic Sight combines optogenetic therapy with glasses containing a camera and a neurocoding device: the camera records images and converts them into code, which is then emitted as light pulses to activate the opsin. the genetically modified ganglion cells. To date, Bionic Sight has treated 13 people, ranging from the very blind to tunnel vision patients.

“It really helps significantly,” says Sheila Nirenberg, founder of Bionic Sight and professor of computational neuroscience at Weill Cornell Medical College.

Think of the large letter “E” on the eye chart that you might examine during a visit to the doctor. The visual acuity of someone who is almost blind is 20/200: what someone with 20/20 vision can see at 60 meters away is only visible at 6 meters to someone who is almost blind.

Many of her patients with retinitis pigmentosa, Nirenberg said, cannot see a letter like the big “E” from just a few feet away. But one patient whose visual acuity was 20/150 (he had to stand 20 feet away from the card to see the letters, while a normally sighted person could stand 50 feet away and see the same letters) is now only 20 meters away. /40. Another patient could not distinguish the colors on playing cards. After receiving the opsin, the patient could not only tell the difference between clubs and diamonds, for example, but could also notice the differences in color.

In another challenge, he tried to spot differences between plastic fruits in front of him. He could see the stem of the apple and distinguish it from oranges and peaches. Ultimately, he was asked to walk through a maze with black squares on the bottom – and he successfully got through it.

“I can’t explain to you how exciting it is,” Nirenberg said. “It’s very hopeful.”

One form of gene therapy to treat blindness has been available for more than five years. Luxturna, a prescription drug approved by the Food and Drug Administration in 2017, is intended for children and adults with a rare genetic mutation that affects the retinal pigment epithelium, the membrane at the back of the retina where the photoreceptors sit. The recipe adds a functional version of the gene to create an epithelium more favorable to the photoreceptors.

“It could slow the progression of the disease,” Hodak said. “But it doesn’t restore any loss.”

That is ultimately the goal of Science Eye. Clinical trials should begin sometime in the next 18 months, Hodak said. The company is also exploring ways to use Science Eye to help people with dry age-related macular degeneration, which unfolds slightly differently than retinitis pigmentosa: Patients first lose high-resolution central vision and then their peripheral vision.

There are milestones to cross for any company using optogenetics to help people improve their vision. More patients enrolled in clinical trials should help fine-tune both opsin delivery and its ability to improve photosensitivity in retinal cells. But Hodak predicts that within the next five years, products will come to market for people like his grandfather.

“You always have to be very careful what you say to patients because they cling to every shred of hope,” Hodak said. “But there are a lot of things on the horizon that are coming together. It’s not at a point where even one thing will fail and derail the entire field. Real progress is coming.”