Brown University nanoparticles help restore lost vision

22 Apr 2025

Infrared stimulation of injected gold nanorods stimulates recovery from AMD, retinal disorders.

A project at Brown University has developed a new approach to the treatment of age-related macular degeneration (AMD) and other retinal disorders.

The research, from the Brown lab of Jonghwan Lee and published in ACS Nano, points towards a new type of visual prosthesis system in which plasmonic gold nanorods are used in combination with a small laser device worn in a pair of glasses.

"This is a new type of retinal prosthesis that has the potential to restore vision lost to retinal degeneration without requiring any kind of complicated surgery or genetic modification," said Jiarui Nie, a postdoctoral researcher at the National Institutes of Health who led the research at Brown.

"We believe this technique could potentially transform treatment paradigms for retinal degenerative conditions."

Use of retinal implants as treatment for AMD has been a topic of study for several decades, with initial development focused on two distinct technologies: subretinal implants placed below the retina, and epiretinal devices positioned within the layers of the retina itself.

Despite consistent progress and benefits for those affected by major sight loss, however, both forms of implant require significant surgical procedures and delivered images that fell short of the clarity and fidelity of natural sight. Finding ways to improve image quality has remained a focus of attention.

The new approach from Brown uses gold nanorods injected into the eye's vitreous humor and incorporated into the retina, to bypass damaged photoreceptors altogether and instead stimulate other cells, termed bipolar and ganglion cells, further up the visual chain. These cells are normally not affected by AMD.

When infrared light is focused on these nanoparticles they generate a tiny amount of heat, which activates the bipolar and ganglion cells in much the same way that photoreceptor pulses do.

Translation to human subjects

The project tested its nanoparticle approach in mouse retinas and in living mice with retinal disorders. After injecting a liquid nanoparticle solution, the researchers used a scanning near-IR laser with a 20-micron spot size to shine patterns of light onto the retinas, and observe resulting cellular activity.

Results showed that the nanoparticles were indeed photothermally stimulating bipolar and ganglion cells in patterns that matched the shapes being projected by the laser.

The fact that laser stimulation caused increased activity in the visual cortices of the mice is an indication that previously absent visual signals were being transmitted and processed by the brain, and indicates that vision had been at least partially restored. This is a good sign for potentially translating a similar technology to humans, said the researchers.

That translation could involve combining the nanoparticles with a laser system mounted in a pair of glasses or goggles. Cameras in the goggles would gather image data from the outside world and use it to drive the patterning of the infrared laser and stimulation of the nanoparticles.

Because the injected nanoparticle solution spreads to cover the whole retina, the new approach could potentially cover someone's full field of vision, commented the team. Using near-IR rather than visual light as stimulation stops the system from interfering with any residual vision a person may retain.

"An intravitreal injection is one of the simplest procedures in ophthalmology," Jiarui Nie said. "We showed that the nanoparticles can stay in the retina for months with no major toxicity, and we showed that they can successfully stimulate the visual system. That's very encouraging for future applications."