Golden Eyes

A team of Brown University researchers has identified a promising new approach that may one day help to restore vision in people affected by macular degeneration and other retinal disorders.

R.I.'S PROVIDENCE [Brown University] A recent study by Brown University researchers suggests that gold nanoparticles, which are tiny pieces of gold that are thousands of times thinner than a human hair, may one day be used to help people with macular degeneration and other retinal disorders regain their vision.

In a study supported by the National Institutes of Health and published in the journal ACS Nano, the team demonstrated that nanoparticles injected into the retina of mice with retinal disorders can successfully stimulate the visual system and restore vision. According to the findings, a novel system for a visual prosthesis that combines nanoparticles with a small laser device worn in a pair of glasses or goggles may one day help people with retinal disorders regain their vision.

Jiarui Nie, a postdoctoral researcher at the National Institutes of Health who led the research while completing her Ph.D. at Brown, stated, "This is a new type of retinal prosthesis that has the potential to restore vision lost due to retinal degeneration without requiring any kind of complicated surgery or genetic modification." She was the researcher in charge of the project. "We believe this technique could potentially change the way retinal degenerative conditions are treated," the authors write.

Nie performed the work while working in the lab of Jonghwan Lee, an associate professor in Brown’s School of Engineering and a faculty affiliate at Brown’s Carney Institute for Brain Science, who oversaw the work and served as the study’s senior author.

Millions of people in the United States and around the world are affected by retinal conditions like macular degeneration and retinitis pigmentosa. Photoreceptors, or the "rods" and "cones" that turn light into tiny electric pulses, are light-sensitive cells in the retina that are damaged by these conditions. These pulses stimulate bipolar and ganglion cells, two types of cells further up the visual chain, which process the photoreceptor signals and send them to the brain.

To get around damaged photoreceptors, this new method injects nanoparticles directly into the retina. Nanoparticles generate a small amount of heat when infrared light is focused on them, activating bipolar and ganglion cells in a manner similar to that of photoreceptor pulses. The strategy has the potential to restore vision that has been lost due to conditions like macular degeneration, which only affect photoreceptors and not bipolar or ganglion cells.

In this new study, the research team tested the nanoparticle approach in mouse retinas and in living mice with retinal disorders. The researchers used patterned near-infrared laser light to project shapes onto the retinas after injecting a liquid nanoparticle solution. The team confirmed that the nanoparticles were stimulating ganglion and bipolar cells in patterns that were consistent with the laser's projected shapes by using a calcium signal to detect cellular activity.

Metabolic markers for inflammation and toxicity indicated that neither the nanoparticle solution nor the laser stimulation caused any observable adverse effects. The researchers were able to demonstrate through the use of probes that laser stimulation of the nanoparticles resulted in an increase in activity in the visual cortices of the mice. This was a sign that the brain was transmitting and processing visual signals that were previously absent. According to the researchers, this indicates that vision had been at least partially restored, which is encouraging for the possibility of applying a technology that is similar to humans.

The researchers envision a system for human use that integrates the nanoparticles with a laser system that is attached to a pair of glasses or goggles. An infrared laser's patterning would be controlled by image data gathered from the outside world by cameras in the goggles. The nanoparticles in people's retinas would then be stimulated by the laser pulses, allowing them to see.

The strategy is comparable to one that was recently granted human use approval by the Food and Drug Administration. The older method involved surgically implanting a small electrode array and a camera system in the eye. Nie claims that the nanoparticle method has a number of significant advantages.

For starters, it’s far less invasive. As opposed to surgery, “an intravitreal injection is one of the simplest procedures in ophthalmology,” Nie said.

Additionally, there are practical advantages. The electrode array's size of approximately 60 square pixels limited the previous method's resolution. The new method has the potential to cover a person's entire field of vision due to the fact that the nanoparticle solution covers the entire retina. Additionally, the system does not necessarily impair a person's residual vision because the nanoparticles respond to near-infrared light rather than visual light.

More work needs to be done before the approach can be tried in a clinical setting, Nie said, but this early research suggests that it’s possible.

“We showed that the nanoparticles can stay in the retina for months with no major toxicity,” Nie said of the research. “And we showed that they can successfully stimulate the visual system. That’s very encouraging for future applications.”

The research was funded by the National Institutes of Health’s National Eye Institute (R01EY030569), the China Scholarship Council scholarship, the Saudi Arabian Cultural Mission scholarship, and South Korea’s Alchemist Project Program (RS-2024-00422269). Co-authors also include Professor Kyungsik Eom from Pusan National University, Brown Professor Tao Lui, as well as Brown students Hafithe M. Al Ghosain, Alexander Neifert, Aaron Cherian, Gaia Marie Gerbaka, and Kristine Y. Ma.