A tiny wireless chip implanted in the eye, combined with smart glasses, has enabled many patients with advanced age-related macular degeneration to regain reading ability. In a clinical trial led by Stanford Medicine, 27 out of 32 participants achieved functional vision within a year. The findings, published in the New England Journal of Medicine, mark the first prosthetic device to provide form vision.
The PRIMA implant, developed at Stanford Medicine, addresses geographic atrophy, an advanced stage of age-related macular degeneration that destroys central vision and affects over 5 million people worldwide. This condition, the leading cause of irreversible blindness in older adults, deteriorates light-sensitive photoreceptor cells in the central retina while leaving processing neurons intact.
The system consists of a small camera on smart glasses that captures visuals and projects them via infrared light onto the 2-by-2-millimeter chip implanted subretinally. The chip converts this light into electrical signals, bypassing damaged photoreceptors to stimulate remaining neurons. Unlike prior devices that offered only light sensitivity, PRIMA delivers form vision, allowing recognition of shapes and patterns.
"All previous attempts to provide vision with prosthetic devices resulted in basically light sensitivity, not really form vision," said Daniel Palanker, PhD, professor of ophthalmology at Stanford and co-senior author. "We are the first to provide form vision."
The trial enrolled 38 patients over 60 with vision worse than 20/320 in at least one eye. Four to five weeks post-implantation, participants began using the glasses, with vision improving over months of training. Of the 32 who completed the one-year study, 27 could read books, labels, and signs; 26 showed meaningful acuity gains, averaging five lines on an eye chart. The glasses feature adjustable zoom up to 12 times, enhanced contrast, and brightness, yielding sharpness akin to 20/42 vision in some.
The photovoltaic implant operates wirelessly without external power. Patients merge prosthetic central vision with natural peripheral vision for better navigation. Side effects, such as ocular hypertension and subretinal hemorrhage, affected 19 participants but resolved within two months without life-threatening issues. Two-thirds reported medium to high satisfaction.
Conceived two decades ago by Palanker, PRIMA evolved through prototypes and animal tests. Future versions aim for grayscale, face recognition, and higher resolution with smaller pixels, potentially approaching 20/20 vision via electronic zoom. The study, co-led by José-Alain Sahel, MD, of the University of Pittsburgh, and Frank Holz, MD, of the University of Bonn, involved international collaborators and funding from Science Corp. and others.