In a pivotal study led by Stanford Medicine in collaboration with international researchers, 32 participants diagnosed with the advanced form of AMD, specifically geographic atrophy, were enrolled. The results, published on October 20th in the prestigious New England Journal of Medicine, revealed that an astounding 27 of these individuals regained the ability to read within a year of receiving the PRIMA implant. This achievement is particularly significant as geographic atrophy progressively destroys central vision, a condition previously considered untreatable and a leading cause of irreversible blindness in older adults, affecting over 5 million people globally.

The PRIMA system represents the first prosthetic eye device to restore usable vision, moving beyond mere light sensitivity to provide what is known as "form vision" – the ability to recognize shapes and patterns. Dr. Daniel Palanker, a professor of ophthalmology at Stanford Medicine and co-senior author of the paper, emphasized this critical distinction: "All previous attempts to provide vision with prosthetic devices resulted in basically light sensitivity, not really form vision. We are the first to provide form vision." This breakthrough is the culmination of decades of dedicated scientific effort, involving numerous prototypes, extensive animal testing, and an initial human trial, originating from Dr. Palanker’s conceptualization two decades ago.

The intricate PRIMA system comprises two essential components: a miniature camera integrated into a pair of advanced smart glasses and a wireless chip surgically implanted in the retina. The camera captures visual information and transmits it via infrared light to the retinal implant. This implant then ingeniously converts the infrared signals into electrical impulses. These electrical signals effectively act as replacements for the damaged photoreceptor cells, the light-sensitive cells in the retina that normally detect light and transmit visual data to the brain. In AMD, these crucial photoreceptors in the central retina deteriorate, leading to significant vision loss. However, a considerable number of the retinal neurons responsible for processing visual information often remain intact, and PRIMA is designed to leverage these surviving structures.

The implant itself is remarkably small, measuring just 2 by 2 millimeters, and is strategically placed in the region of the retina where photoreceptors have been lost. Unlike natural photoreceptors that respond to visible light, the PRIMA chip is designed to detect infrared light emitted by the glasses. Dr. Palanker explained the rationale behind this choice: "The projection is done by infrared because we want to make sure it’s invisible to the remaining photoreceptors outside the implant." This design allows patients to simultaneously utilize their existing natural peripheral vision and the newly restored artificial central vision, a synergy that significantly enhances their ability to navigate their environment and orient themselves. "The fact that they see simultaneously prosthetic and peripheral vision is important because they can merge and use vision to its fullest," Dr. Palanker added.

A key advantage of the PRIMA device is its photovoltaic nature, meaning it relies solely on light to generate its electrical current. This allows it to operate wirelessly and be safely implanted beneath the retina, eliminating the need for external power sources or transcutaneous wires that were characteristic of earlier artificial eye technologies.

The recent clinical trial involved 38 participants, all over the age of 60, who had advanced geographic atrophy due to AMD and experienced vision worse than 20/320 in at least one eye. Following the implantation of the chip in one eye, patients began using the smart glasses approximately four to five weeks later. While some individuals could discern patterns immediately, all participants experienced gradual improvements in their visual acuity over several months of dedicated training. Dr. Palanker likened this training period to the mastery required for cochlear implants, noting, "It may take several months of training to reach top performance."

The results of the one-year trial were exceptionally encouraging. Of the 32 participants who completed the study, 27 were able to read, and 26 demonstrated clinically meaningful improvement in their visual acuity – defined as the ability to read at least two additional lines on a standard eye chart. On average, participants’ visual acuity improved by five lines, with one individual experiencing an impressive gain of twelve lines. The prosthesis proved highly functional in daily life, enabling participants to read books, decipher food labels, and recognize subway signs. The adjustable features of the glasses, including contrast and brightness settings and up to 12 times magnification, played a crucial role in optimizing their visual experience. A significant two-thirds of the participants reported medium to high levels of satisfaction with the device.

While the trial reported side effects in 19 participants, including ocular hypertension, peripheral retinal tears, and subretinal hemorrhage, none of these were life-threatening, and nearly all resolved within two months, underscoring the overall safety profile of the implant.

Looking towards the future, Dr. Palanker and his team are actively developing enhancements for the PRIMA system. Currently, the device provides black-and-white vision, but the development of new software is on the horizon to enable a full range of grayscale. This advancement is crucial for applications like face recognition, which is a high-priority request from patients. "Number one on the patients’ wish list is reading, but number two, very close behind, is face recognition. And face recognition requires grayscale," explained Dr. Palanker.

Furthermore, efforts are underway to engineer chips with higher resolution. The current resolution is limited by the 100-micron width of the pixels, with 378 pixels per chip. A new version, already tested in rats, aims to achieve pixels as small as 20 microns, potentially accommodating 10,000 pixels per chip. Such an improvement could grant patients 20/80 vision, with the added benefit of electronic zoom potentially bringing them close to 20/20 acuity. The team also plans to investigate the applicability of the PRIMA device for other forms of blindness caused by photoreceptor loss. "This is the first version of the chip, and resolution is relatively low," Dr. Palanker stated. "The next generation of the chip, with smaller pixels, will have better resolution and be paired with sleeker-looking glasses."

The groundbreaking research was a collaborative effort involving numerous institutions worldwide, including the University of Bonn (Germany), Hôpital Fondation A. de Rothschild (France), Moorfields Eye Hospital and University College London, Ludwigshafen Academic Teaching Hospital, University of Rome Tor Vergata, Medical Center Schleswig-Holstein, University of Lübeck, L’Hôpital Universitaire de la Croix-Rousse and Université Claude Bernard Lyon 1, Azienda Ospedaliera San Giovanni Addolorata, Centre Monticelli Paradis and L’Université d’Aix-Marseille, Intercommunal Hospital of Créteil and Henri Mondor Hospital, Knappschaft Hospital Saar, Nantes University, University Eye Hospital Tübingen, University of Münster Medical Center, Bordeaux University Hospital, Hôpital National des 15-20, Erasmus University Medical Center, University of Ulm, Science Corp., University of California, San Francisco, University of Washington, University of Pittsburgh School of Medicine, and Sorbonne Université. Funding for this transformative study was provided by Science Corp., the National Institute for Health and Care Research, Moorfields Eye Hospital National Health Service Foundation Trust, and University College London Institute of Ophthalmology, paving the way for a future where vision loss may no longer be an insurmountable barrier.