The Implant System that Seeks to Restore Vision Loss
More than 5 million people worldwide experience irreversible blindness due to geographic atrophy in age-related macular degeneration (AMD).
While current treatments can slow the progression of AMD, they do not restore vision and require eye injections every 1 to 2 months. To address this issue, a team of researchers, including the University of Pittsburgh's José-Alain Sahel, MD, is developing the photovoltaic retina implant microarray (PRIMA) system, an implant system that uses infrared light to restore lost sight. A recent study in the New England Journal of Medicine examined the results of the implant after 12 months.
AMD is an eye disease common in older adults that occurs when the macula, which processes central vision, deteriorates, leading to gradual vision loss. In one type of AMD, which is called “dry AMD” or “geographic atrophy”, this process occurs over the course of several years. Geographic atrophy damages the photoreceptors, which convert the light entering the eye into electrical signals sent to the brain, enabling vision. When photoreceptors deteriorate in certain locations in the eye, light cannot be converted into signals, creating permanent blind spots.
How Infrared Light Restores Lost Sight
The photovoltaic retina implant microarray (PRIMA) system uses an implant and glasses to replace the lost photoreceptors. The PRIMA implant is 2 mm × 2 mm thick, made of a crystalline silicon array, and contains photovoltaic (light-converting) pixels. This implant is surgically placed under the retina. The PRIMA glasses have a camera mounted on the frame that captures images and uses infrared light to project the image onto the implant. Like a puzzle piece, the implant fits into the missing vision spots, and the photovoltaic pixels act like a photoreceptor to convert light into electrical signals that are sent to the brain to create vision.
The PRIMA clinical study included 38 participants, 60 years of age or older, with a diagnosis of geographic atrophy due to AMD in both eyes, a minimum vision of 1.2 logMAR (logarithm of the Minimum Angle of Resolution, the standard way to measure visual acuity) or 20/320, and an atrophy larger than the implant. Participants were recruited from 17 medical centers across five European countries, and all received the implant. Photos of participants' eyes were taken before and after the implant surgery. After 12 months, 32 of 38 of the participants were tested on their central vision perception, and 33 of 38 were tested on the implant’s resolution.
The study found that the implant and glasses system significantly improved participants’ central vision. The average improvement of patients’ vision was 0.51 logMAR, meaning they could read about 25 more letters on the logMAR chart than before. With the implant alone, participants’ vision was about 20/400. With glasses, they were able to read smaller fonts and text at about 20/42. Additionally, 84% of participants were able to use the system in their own homes to read letters, numbers, and words.
A Closer Look at PRIMA’s Impact
While other vision-assistive devices and implants have been developed, PRIMA is implanted beneath the retina and restores vision in the blind spot, allowing patients to move their eyes rather than their heads to direct their gaze. PRIMA also has fewer surgical risks than previous implants and devices and is wireless, making it less bulky.
In the past, the damage to central vision caused by geographic atrophy and AMD has been irreversible, making the work of this study critical. Not only does the system restore lost vision, but it is also accessible, allowing users to read in their own homes. With further development, this system could be the next generation of visual prosthetics, and restore the vision lost by the 5 million people with irreversible blindness due to the condition.