Imagine slowly losing the center of your vision, like a camera lens fading to fog. That's what happens with geographic atrophy, a severe form of age-related macular degeneration (AMD). It's the world's leading cause of permanent blindness, affecting more than five million people.
Right now, there's no way to restore lost sight. Past efforts using visual prosthetics gave people a flicker of light but not real shapes or meaningful images. It's like sensing a flashlight in the dark but never seeing the room it's in.
In a groundbreaking clinical trial, Stanford Medicine researchers and global collaborators have developed a wireless retinal implant called PRIMA that's helping people with untreatable vision loss see again, not just light, but actual shapes and patterns. That's what scientists call form vision.
PRIMA, short for photovoltaic retina implant microarray, is a cutting-edge system designed to restore vision. It involves implanting a tiny chip beneath the retina. Special glasses then beam invisible near-infrared light onto the chip. The chip converts this light into electrical signals, which in turn stimulate the retina and transmit visual information to the brain, allowing patients to perceive shapes and patterns once lost to vision impairment.
The PRIMA system works like a high-tech tag team. A tiny camera is attached to a pair of glasses. It captures images and sends them immediately as infrared light to a wireless chip implanted in the eye. That chip replaces damaged photoreceptors. It converts the light into electrical signals, which the brain can interpret as vision.
What's smart about the PRIMA system is that it restores the central part of your vision, where you focus and read, without interfering with your natural side vision. So users can spot shapes and patterns straight ahead, while still relying on their peripheral sight to move around and stay aware of their surroundings.
The study included 38 people with geographic atrophy. This condition harms the retina by damaging the central photoreceptors (which help us to see fine details).
The good news is that most patients still have some working cells in the edges of their vision, and the nerve pathways that carry visual signals to the brain are still intact. The new device takes advantage of what is preserved.
A small 2-x-2-mm chip is inserted into the region of the retina that has lost its light-sensing cells, where vision has diminished. Natural light is not necessary for this chip to function. Instead, it reacts to invisible infrared signals transmitted through specialized glasses. Replacing the damaged photoreceptors helps restore sight where it is most needed.
"The projection is done by infrared because we want to make sure it's invisible to the remaining photoreceptors outside the implant," said co-senior author Daniel Palanker, PhD, a professor of ophthalmology.
To test the PRIMA system, researchers ran a carefully designed clinical trial across multiple centers. They invited participants with advanced vision loss from geographic atrophy to try the PRIMA glasses.
Each person's vision was checked with and without the device 6 and 12 months after the implant. The goal? To see if their sight improved meaningfully, specifically if they could read smaller letters or see finer details (a shift of at least 0.2 on the logMAR scale). Researchers also kept a close eye on safety, tracking any serious side effects from the implant or procedure over the year.
The results were impressive. After a year with the PRIMA system, 26 out of 32 participants showed a significant improvement in their ability to see; they went from blurry outlines to recognizable shapes.
There were some side effects: 26 serious events were reported in 19 people, but most happened within two months of surgery, and nearly all of those (95%) cleared up quickly.
Significantly, the implant didn't interfere with the patients' natural side vision. Their peripheral sight stayed just as it was before the procedure, giving them a blend of restored central vision and preserved natural vision for better orientation and mobility.
The PRIMA system gave patients back something they'd lost, central vision. Over 12 months, it didn't just restore light perception; it helped people see shapes and patterns more clearly.
"The fact that they see simultaneously prosthetic and peripheral vision is important because they can merge and use vision to its fullest," Palanker said.
Because the PRIMA chip is photovoltaic, it runs on light; it doesn't need wires or batteries.
Participants used the device in everyday life: reading books, checking food labels, and even navigating subway signs. The smart glasses let them tweak contrast and brightness, and zoom in up to 12 times. About two-thirds said they were satisfied with the device, rating it medium to high.
Right now, the PRIMA device lets users see in black and white, no shades of gray just yet. But Palanker is working on new software that will soon unlock the full grayscale spectrum, adding depth and detail to what patients can see.
"Number one on the patients' wish list is reading, but number two, very close behind, is face recognition," he said. "And face recognition requires grayscale."
He's also designing next-gen chips to sharpen vision even further. Today's chip has 378 pixels, each 100-microns wide. The new version, already tested in rats, could shrink pixels to just 20 microns and pack in 10,000 of them, bringing much higher resolution.
And he's not stopping there. Palanker plans to explore how PRIMA could help with other forms of blindness caused by lost photoreceptors.
The study was published in the journal The New England Journal of Medicine.
Source: Stanford Medicine
