A solar panel for the retina: how subretinal implants restore vision where drugs cannot
Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the developed world, affecting more than 5 million people globally. In its advanced form, geographic atrophy, the light-sensitive cells of the central retina die off, leaving a blind spot in the middle of the visual field. Patients can see peripherally but cannot read, recognize faces, or drive. Until recently, there was no treatment that could restore vision to the atrophied area.
The PRIMA system, developed by Science Corporation and described in the New England Journal of Medicine (DOI: 10.1056/NEJMoa2501396), takes a fundamentally different approach from earlier retinal prostheses. Instead of mounting a camera on a pair of glasses and sending processed video signals to electrodes implanted in the retina, PRIMA uses the eye itself as the optical system. The implant is a 2-millimeter-wide photovoltaic chip placed beneath the retina, in the subretinal space. The patient wears glasses that project near-infrared light patterns directly onto the chip. The chip converts the light into electrical current, stimulating the surviving retinal neurons to send signals to the brain.
It is, in effect, a solar panel for the retina.
How it differs from earlier approaches
The most widely known retinal prosthesis, the Argus II (“bionic eye”), used an external camera mounted on glasses, a video processing unit worn on the belt, and an electrode array on the surface of the retina. The system worked, patients could detect light and motion, but resolution was limited by the number of electrodes and the fact that the camera’s viewpoint did not move with the eye.
PRIMA eliminates the external camera entirely. The glasses project near-infrared images at 880 nanometers, invisible to the eye, directly through the natural optics of the pupil and lens. The patient’s own eye movements control what they see, because the image enters through their natural visual pathway. The subretinal chip, measuring just 2 mm across, contains 378 individual pixels, each of which is a miniature photovoltaic cell that converts the incoming light into electrical stimulation.
Because the chip is placed beneath the retina, in the subretinal space where the photoreceptors used to sit, the electrical stimulation reaches the bipolar cells and ganglion cells that would normally receive signals from the photoreceptors. The brain receives signals that preserve the spatial organization of the visual field, unlike surface electrode arrays that produce more diffuse stimulation.
Clinical trial results
The PRIMAvera study enrolled 38 participants with geographic atrophy and severe central vision loss (visual acuity of at least 1.2 logMAR, roughly the level of legal blindness). The implant was placed surgically in one eye, and participants were assessed at 6 and 12 months.
Of the 32 participants who completed 12 months of follow-up, 26, 81 percent, showed a clinically meaningful improvement in visual acuity of at least 0.2 logMAR when using the system compared with baseline. Using statistical imputation to account for the 6 participants who did not complete the study, the estimated improvement rate was 80 percent.
Serious adverse events occurred in 19 participants, for a total of 26 events. Crucially, 81 percent of these events occurred within the first two months after surgery, and 95 percent of those resolved within two months. The events were primarily surgical, related to the implantation procedure rather than the device itself, and natural peripheral vision was not affected.
Where it fits in the AMD treatment landscape
AMD is unusual among major causes of blindness in that there are now treatments for some forms but not others. Wet AMD, the form caused by abnormal blood vessel growth, can be managed with anti-VEGF injections. Geographic atrophy, the advanced dry form, has no approved restorative therapy. The available treatments slow progression but do not bring back lost photoreceptors.
The PRIMA system does not regenerate photoreceptors. It replaces their function electronically. This means it works only in patients whose inner retinal neurons, the bipolar and ganglion cells, are still intact. In geographic atrophy, these cells are generally preserved even after the photoreceptors have died, which is why the approach is viable.
The implant is now available in Europe, with a US launch targeted for 2027, pending FDA approval. It will not restore normal vision, the 378-pixel array provides pattern vision sufficient for reading large print and recognizing faces, not for fine detail. But for patients with no other option, the difference between seeing a face and seeing only a blur is not a matter of degree. It is a different quality of life.
Reference: Holz et al., “Subretinal Photovoltaic Implant to Restore Vision in Geographic Atrophy Due to AMD,” New England Journal of Medicine 394:232-242 (2026). DOI: 10.1056/NEJMoa2501396.