Bionic Eye Restores Central Vision in AMD Patients with Prima Photovoltaic Chip

In this Science Weekly episode, Moorfields Eye Hospital and Stanford-led researchers discuss the Prima retinal implant, a tiny 2x2 mm chip with 378 photovoltaic pixels implanted at the center of the retina. The system relies on infrared light guided from glasses with an integrated camera and a pocket processor to stimulate the remaining retinal neurons, producing central vision in patients previously legally blind due to AMD. While the initial results show promise in reading letters and words in black and white, the experience requires intense concentration and rehabilitation to maximize benefits. The trial involved 32 patients, with 27 regaining some central vision. The program highlights a path toward regulatory approval and ongoing refinements in hardware and software as the field explores options such as stem cell or gene therapies alongside bionic approaches.

Overview and Context

The Guardian Science Weekly episode focuses on advances in restoring sight for people with age-related macular degeneration (AMD), a leading cause of vision loss in the UK. The trial centers on the Prima retinal implant, a miniaturized device designed to substitute lost photoreceptors by electrically stimulating the remaining retinal neurons. AMD damages the macula, eroding central vision, leaving some peripheral sight intact. The Prima approach aims to convert visual information into infrared excitation that the brain can interpret as meaningful images, enabling tasks such as reading, recognizing signs, and even crossword puzzles.

"I could have cried when I looked because I haven't seen letters for so long, and then I lit up a word and it was overwhelming" - Sheila Irwin, patient

The episode features Mahe Muckett, a Moorfields consultant surgeon and associate professor at University College London, who explains the device’s concept, testing, and patient outcomes. The discussion places the Prima chip within the broader context of retinal prostheses, highlighting the shift from passive light-sensing implants to active stimulation of retinal circuits. The trial’s significance lies in restoring useful central vision for many participants, a dramatic improvement over prior visual prostheses that produced limited, often abstract light cues.

How the Prima Device Works

The Prima system comprises a tiny chip implanted near the center of the retina (the macula) and a peripheral setup that captures real-world scenes and translates them into infrared light to drive the chip. The core is a 2 by 2 millimeter device with 378 pixels, each a photovoltaic cell that converts infrared illumination into electrical stimulation for the overlying retinal neurons. An array of electrodes acts as the stimulating interface, akin to miniature solar panels feeding signals to the retinal network. Glasses worn by the patient hold a camera that captures the scene, while a pocket processor refines the image in real time and transmits infrared pulses back to the chip. The process is instantaneous, with the system designed so infrared light does not impinge on any remaining peripheral vision. The result is a form of artificial vision that, at present, yields black-and-white central vision and enables recognition of letters and shapes as rehabilitation progresses.

"There will be new developments coming along" - Mahe Muckett, Moorfields Eye Hospital

Clinical Experience and Patient Impact

In the trial, the implant was placed in 32 patients, with 27 gaining the ability to read again, a remarkable outcome given their central vision loss. Patients undergo a rehabilitation program after implantation, beginning with device activation about a month post-surgery. Early visions are noisy, but the processing unit gradually refines the image as patients learn to focus on objects, adjust brightness and contrast, and utilize zoom features to enhance legibility on signs, letters, or numbers. For many participants, the device restores a meaningful central view that had been absent for years, dramatically improving daily activities and emotional well-being. Sheila Irwin’s experience—reading letters, completing crossword puzzles, and engaging with books—embodies the kind of functional gains the technology seeks to deliver. The episode emphasizes that the device represents a tool to regain central vision rather than a curative treatment for AMD, requiring training and adaptation to maximize benefit.

"The main thing is that they can actually see now in their central vision" - Mahe Muckett, Moorfields Eye Hospital

Regulatory Outlook and the Path Forward

Mahe Muckett explains that medical device trials can be smaller than drug trials, yet still satisfy regulatory requirements (e.g., FDA, MHRA) for approval, paving the way for broader adoption in health markets. The field faces continued optimization across hardware and software, as well as exploration of complementary therapies such as stem-cell or gene-based approaches. The interview suggests the Prima device could herald a new era in artificial vision, with refinements to the glasses, image processing, and user rehabilitation likely to expand the device’s utility and the speed with which patients can adapt to using the system. The story leaves room for optimism that the combination of proper device design, patient training, and regulatory approval could transform the landscape of sight restoration for AMD and related retinal diseases.

"There is a start of a new era" - Mahe Muckett, Moorfields Eye Hospital