Chinese researchers have unveiled a new class of retinal prosthesis that relies on nanotechnology to restore the light response. Unlike other subretinal prostheses, the new device—an array of gold-flecked nanowires—replaces damaged photoreceptors and interfaces directly with neurons, averting the need for additional electronic hardware.
If the findings hold up in humans, the device could potentially aid people with degenerative eye conditions such as retinitis pigmentosa or macular degeneration. The approach might also prove useful for reversing vision loss from nondegenerative conditions, such as trauma or retinal detachment.
“The authors have taken a novel approach to fixing a problem that affects the vision of tens of millions of people worldwide,” says Sunir Garg, MD, co-director of the retina research unit at Wills Eye Hospital and Editor-in-Chief of Retina Times.
One existing retinal prosthesis, the Argus II (Second Sight), relies on glasses with a built-in video camera to transmit information to an implanted chip. Another device, the Retina Implant Alpha AMS (Retina Implant AG) simulates photoreceptors from its position under the retina, but requires an external battery pack. Last year, researchers edged closer to a fully implantable prosthesis, constructed from light-sensitive polymers, but it was unclear how well that device interfaced with the retina.
The new prosthesis was tested in a mouse model of degenerative blindness, researchers reported March 9 in Nature Communications. The artificial photoreceptors respond to green, blue and near-ultraviolet light with an “impressive” spatial resolution of 50 microns, says Jennifer Lim, MD, director of the retina service at the Eye and Ear Infirmary at the University of Illinois in Chicago.
“This is precisely what is lacking in current approaches: replacing defunct photoreceptors with artificial ones that can use the electrical wiring inherent in the retina,” says Dr. Lim, who is leading the UIC surgical team in a phase 4 trial of the Argus II. “These scientists have succeeded in engineering a nanoparticle photoreceptor that appears to be able to relay signals to the ganglion cells in blind mice, which then have cortical responses to light.”
a) Location of implant; b) side-by-side comparison showing location of the implanted nanowire (NW) array.
Both Drs. Garg and Lim agree that more work is needed to determine if the device will work in humans, and whether it can replace photoreceptors damaged by either degenerative diseases or trauma.
“However, I believe it is an elegant method and engineering triumph that hopefully will be able to truly replace the defective photoreceptors in patients blind from photoreceptor disease,” Dr. Lim says.