Five people with severe vision loss will have an experimental chip implanted in their eyes to help them see. French regulators last week approved the trial of the bionic vision implant, which will be placed in people with an advanced type of retinal disease called dry age-related macular degeneration, or dry AMD.
Developed by Pixium Vision in Paris, the wireless chip acts as a conduit of communication between the eye and the brain using electrical stimulation. The trial represents the first time such a chip has been used to treat dry AMD, the leading cause of vision loss in people over age 50.
Other visual prostheses have been brought to market, but aim to treat people with rare conditions such as retinitis pigmentosa. Second Sight in Sylmar California commercialized the first such bionic eye after it received approval from US regulators in 2013. Retina Implant in Reutlingen, Germany also markets an implantable chip to treat retinitis pigmentosa, as does Pixium with its 150-electrode chip, called IRIS 2.
So far, the resolution of restored vision from these devices has been rather low. Pixium aims to improve upon that with its wireless 378-electrode chip, called PRIMA. “What people [with AMD] ideally want is to read again and to recognize faces,” says Khalid Ishaque, CEO of Pixium.
Pixium’s technology was born out of Daniel Palanker’s lab at Stanford University. It’s designed to facilitate communication between the eye and the brain which, due to disease, has broken down. The PRIMA chip provides the missing link in that communication using electrical stimulation that codes for information in the visual scene.
The 2 x 2 millimeter square implant is 30 microns thick—about a third of the thickness of a human hair. It is surgically implanted under the retina, or subretinal space. To function, it must be paired with an external camera and a pocket-sized computer.
The user wears a pair of glasses equipped with a camera that senses changes in the visual scene. The image is transmitted to the pocket computer, which transforms the visual events into invisible near-infrared light. The computer pulses those signals back to the glasses, which projects the invisible light beam on the retina and the implanted chip. The chip then converts the signals into electrical current, stimulating nearby bipolar cells. That stimulation kickstarts a pathway of communication that travels to the optic nerve and eventually to the brain.
Bonus: The infrared light from the glasses also powers the implant—no wires or onboard powering needed. This makes for a short surgery—less than 90 minutes, compared with three to eight hours for previously developed devices.
The challenge with electrical stimulation anywhere in the body, including that of the eye, is figuring out the code—the language of electrical signals that the body’s nervous system normally uses to convey information to and from the brain. Pixium and its research collaborators have invested significantly in studying animal models, testing different types of electrodes and stimulation parameters in the eye in an attempt to decode the language.
Still, the electrical language from one person to the next will differ, Ishaque says. In the upcoming trial, the parameters of the stimulation will have to be custom fitted trial-and-error style for each patient.
The stimulation will be targeted at the patients’ central vision. For people with advanced dry AMD, things in the middle of the gaze appear distorted or dark, often leaving the person with only cloudy peripheral vision. Currently there are no treatments to restore lost vision in people with the disease.
One of the risks of having an implant like this in people with AMD is the potential to damage the patient’s remaining peripheral vision. That’s the “principle risk” of targeting people with AMD, says Ishaque. But permanent damage to peripheral vision is “unlikely,” he says, based on the company’s testing of the chip on non-human primates.
The green light for the trial came from the French regulatory body Agence Nationale de Securite du Medicament et des Produits de sante (ANSM). The five people to be recruited for the study must have a very advanced form of dry AMD, with no perception in their central vision, says Ishaque. A chip will likely be implanted in the first patient before the end of the year, he says.
Pixium’s PRIMA device is under review by regulators at the US Food and Drug Administration (FDA), according to Ishaque.