Scientists have used an eye implant to improve the vision of dozens of people left functionally blind due to age-related macular degeneration (AMD). The implant, measuring 2 by 2 millimeters and just 30 micrometers thick, is surgically inserted under the retina to replace light-sensitive cells lost due to the disease.
The clinical trial described today in New England Journal of Medicinewhich involved 38 people with late-stage AMD whose retinas had severely degenerated. One year after device implantation, 80% of participants experienced clinically significant improvement in vision.
“Where this dead retina was a complete blind spot, vision was restored,” says study leader Frank Holz, an ophthalmologist at the University of Bonn in Germany. “Patients could read letters, words and could function in daily life.”
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Despite some minor events associated with surgical implantation, the study's safety monitoring panel found that the device's benefits outweighed its risks. In June, the device's owners, San Francisco-based neurotechnology company Science Corporation, applied for certification that would allow the device to be sold in the European market.
“I think this is an exciting and significant study that was well designed and analyzed and offers hope for improved vision in patients for whom this was more 'science fiction' than reality,” says Francesca Cordeiro, an ophthalmologist at Imperial College London.
Restored vision
AMD is the most common form of permanent blindness in older adults. There are two main types: wet and dry AMD. The current work studied people with the dry form of AMD, which affects about 5 million people worldwide. In dry AMD, the light-sensitive cells in the central part of the retina die over several years, leaving affected people with peripheral vision but no high-acuity central vision. “They can’t recognize faces, they can’t read, they can’t drive, they can’t watch TV,” Holtz says.
Dying light-sensitive cells (rods and cones) convert light into electrochemical signals that are transmitted to other types of neurons in the retina, which then send messages to the image processing areas of the brain. Because retinal neurons survive AMD, scientists have concluded that a light-sensitive implant that electrically stimulates the retina according to the pattern of photons hitting it could restore vision.
The implant, called PRIMA (for Photoelectric Retinal Implant Microchip), was originally developed by Paris-based Pixium Vision and was acquired by Science Corporation last year. Unlike previous retina devices, it is wireless. And because it is photovoltaic, the photons that activate it also provide the energy source to generate electrical power.
It is used in conjunction with glasses containing a camera that captures images and converts them into patterns of infrared light, which they transmit to the retinal implant.
Optimal use of the system, which allows users to zoom in and out on targets and adjust contrast and brightness, requires months of intensive training, Holtz said.
In the current study, 38 participants were treated at 17 clinical sites in 5 European countries, and 32 participants were tested one year after implantation. Twenty-six of them showed clinically significant improvement in vision, which on average meant being able to see two lines further than a standard vision test letter chart. Overall, the vision of most participants was close to the solution achievable with PRIMA.
By the end of the study, most recipients were using PRIMA at home to read letters, words, and numbers. Of the 32, 22 said their user satisfaction was average or high.
Slow reading
However, the user's daily quality of life questionnaire did not reveal significant overall improvements. A retinal degeneration researcher working on a cure for vision loss, who wished to remain anonymous to avoid retaliation, spoke to Nature and expressed concern that intensive vision training and motivation to obtain an interesting medical device may have led to improved test scores. They said the results would be more reliable if gains were demonstrated compared to a randomized placebo group that received the glasses and training protocols but did not have the implant.
Holtz also acknowledges that the current system has limitations and says he expects future implants to be more effective. “This first major breakthrough was the starting point for further improvements,” he says.
Another issue is the current maximum visual acuity achievable with the current device. The PRIMA system has a total of 381 pixels, each with an area of 100 micrometers. And Holtz admits that reading users is “not a fast, smooth reading.” The vision presented is also in black and white rather than color.
Holtz says Daniel Palinker, a physicist at Stanford University in Palo Alto, California, who originally developed the device, has ideas about how to one day achieve color vision. The next generation device, which is larger than PRIMA and contains smaller pixels, should provide better visual acuity. “This is the beginning of the journey,” Holtz says.
Although the device was tested on people with AMD, it could also help restore vision to people suffering from other diseases in which photoreceptor cells die but other retinal neurons remain functional, such as retinitis pigmentosa.
Retinal implants are not the only approach being developed to solve this problem. Other researchers are exploring the use Stem cell therapy for photoreceptor regeneration; optogenetic therapy, in which light-sensitive proteins are injected into remaining retinal cells; and even implants that are inserted into the visual cortex of the brain.
“It’s a huge, dynamic space, and there are a lot of different approaches now,” Holtz says. “No one knows what will happen in the end.”
This article is reproduced with permission and has been first published October 20, 2025.
