Patients blinded by an advanced form of macular degeneration have regained the ability to read after receiving the PRIMA implant, a retinal device that pairs a two-square-millimetre photovoltaic chip with camera-equipped eyeglasses. The system, developed by California-based Science Corporation, was approved in Europe in July and is awaiting clearance from the U.S. Food and Drug Administration, MIT Technology Review reported.
More than 5 million people worldwide live with geographic atrophy, the advanced form of age-related macular degeneration (AMD) in which light-sensing cells in the centre of the retina die off, leaving a growing blind spot in the middle of vision. Until now, no treatment could restore their sight.
How the PRIMA implant works
The PRIMA implant takes advantage of the fact that AMD destroys only the photoreceptors, the cells that convert light into electrical signals, while leaving the rest of the retina’s wiring intact. The chip is surgically placed beneath the retina, where it mimics the lost photoreceptors and transmits visual information to healthy eye circuitry and on to the brain.
Glasses fitted with a miniature front-facing camera capture what the wearer is seeing in real time, at roughly five megapixels and 30 frames per second. A processor converts the video into pulses of near-infrared light that are projected through the pupil onto the chip, which turns them into electrical signals. Because the stimulation uses infrared light, it does not interfere with the surviving natural photoreceptors around the implant, allowing the brain to merge restored central vision with the patient’s remaining peripheral sight. The PRIMA implant also includes a zoom function so users can magnify whatever they are looking at.
“We’re leveraging all of the body’s own natural functions to process and transmit the information,” said Frank Brodie, an ophthalmologist at the University of California, San Francisco, who serves as Science Corporation’s chief medical officer for ophthalmology.
PRIMA implant trial results hold up at three years
The results come from PRIMAvera, a clinical trial that implanted the PRIMA device in 38 people across 17 centres in five European countries. All had geographic atrophy, and their average vision at the start of the study was about 20/460, meaning they could not reliably make out even the largest letter on a standard eye chart.
At 12 months, 32 of the 38 participants could be evaluated, and their eyes had gained an average of 24.5 letters on a standard vision chart, roughly five lines, a result published in The New England Journal of Medicine. More than 80 per cent of recipients were able to read, do crosswords and use their phones after visual training sessions.
At 36 months, among the 18 participants still evaluable at that later point, the average gain had grown to 29 letters, nearly six lines, bringing vision to roughly 20/120. Seventy-eight per cent improved by at least 15 letters, or three lines, a threshold researchers consider clinically meaningful. “In clinical trials, PRIMA is working better at month 36 than it did at month six,” said Max Hodak, co-founder and chief executive of Science Corporation. Engineers say the PRIMA implant is designed to last for the lifetime of the patient, since the chip contains no battery and draws its power from the infrared light projected by the glasses. The three-year figures come from a conference presentation rather than a peer-reviewed paper, and the trial had no control group, so every participant received the implant.
PRIMA implant approval timeline and what comes next
Europe authorised the system in July, and it is now approved in 30 European countries, according to a review in Tech Xplore. U.S. regulators have not yet cleared it, and Science Corporation has not said when it expects an FDA decision. Analysts note that the PRIMA implant faces a pivotal test in the U.S. review, where regulators will weigh the durability of the three-year gains against the risks of subretinal surgery. The technology was designed by Daniel Palanker at Stanford School of Medicine and was originally developed by the French start-up Pixium Vision, which sold the PRIMA implant to Science Corporation for about 4 million euros after facing bankruptcy.
The device arrives after earlier bionic-eye efforts fell short. The Argus II system received FDA authorisation in 2013 but was discontinued in 2019 after failing to deliver convincing results. Because AMD is far more common than the inherited retinal diseases treated by earlier devices, the commercial appeal of the PRIMA implant is considerable. But the complex subretinal surgery is far from risk-free, and most AMD patients still have useful peripheral vision, which raises the stakes if anything goes wrong. For now, the company says its priority is completing the regulatory path in the United States while continuing to follow the European trial participants.