Gold nanoparticles in the eye have potential use as optical prosthesis.

Researchers at Brown University have developed a new vision-restoring technique using gold nanoparticles and infrared light, offering a non-invasive alternative to retinal implants for people with degenerative eye diseases.

The approach works by bypassing the retina's damaged photoreceptors – cells typically lost in conditions like macular degeneration and retinitis pigmentosa – and instead activates the intact cells beneath them.

After a solution of gold nanoparticles is injected into the eye, near-infrared light triggers them to produce tiny amounts of heat, which in turn stimulates the bipolar and ganglion cells responsible for sending visual signals to the brain, providing a novel workaround for vision loss that doesn't rely on implanted electrodes or invasive surgery.

This technique marks a shift toward a new class of visual prosthetics that avoid many of the drawbacks of conventional retinal implants, which often require surgically embedded electrode arrays paired with external cameras and processors.

In contrast, the nanoparticle-based system requires only a straightforward injection into the eye and works in tandem with a lightweight external device – typically a pair of goggles equipped with a laser and camera. The goggles capture visual data from the environment, convert it into patterns of near-infrared laser pulses, and project those pulses into the eye. Activated by the laser light, the nanoparticles then stimulate the retinal cells to transmit visual information to the brain, effectively mimicking the natural visual process.

Minimal invasiveness and improved results

Macular degeneration and retinitis pigmentosa are retinal disorders that affect millions globally, damaging the photoreceptors in the eye that convert light into electrical pulses to activate bipolar and ganglion cells, which process visual signals and transmit them to the brain.

One of the most significant advantages of the nanoparticle system is how non-invasive it is compared to existing prosthetic technologies. The procedure to deliver the particles – an intravitreal injection – is already a routine and relatively low-risk treatment.

"An intravitreal injection is one of the simplest procedures in ophthalmology," said Jiarui Nie, a postdoctoral researcher at the National Institutes of Health who led the research while completing her Ph.D. at Brown.

This makes the technology more accessible to patients and, in terms of performance, could even offer higher-resolution vision.

Earlier devices relied on electrode arrays limited to around 60 pixels, severely restricting visual clarity, whereas the nanoparticle approach allows for much higher potential resolution, as the particles can disperse across the retina and respond to finely tuned laser patterns.

The use of near-infrared light – which doesn't interfere with visible light – also allows the system to remain compatible with any residual natural vision a person may still have.

Success in mice

To test the feasibility of this technique, the researchers conducted experiments both in isolated mouse retinas and in living mice suffering from retinal degeneration. After injecting a solution of gold nanoparticles into the eye, they projected various shapes onto the retina using a patterned near-infrared laser.

Calcium imaging confirmed that the bipolar and ganglion cells responded to the laser patterns, replicating the visual stimulation normally triggered by healthy photoreceptors. Additionally, brain imaging showed increased activity in the visual cortex of the treated mice, a strong indicator that the brain was receiving and processing visual information once again.

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

While still in the early stages, this technology shows strong promise, with the research team noting that the gold nanoparticles remained stable in the retina for several months without triggering any harmful immune responses.

This suggests the method could be safe for long-term use. If further studies confirm safety and efficacy in larger animals and eventually humans, the approach could offer a transformative new treatment for millions of people affected by vision loss due to retinal diseases. Because the technology doesn't rely on genetic modification or complicated surgery, it could be deployed more broadly and potentially at a lower cost than current prosthetic systems.

Next steps and future prospects

Although the results so far are promising, the researchers caution that further development is needed before clinical trials can begin, with key next steps including refinement of the external interface, improved precision and sensitivity of nanoparticle stimulation, and confirmation of long-term safety and biocompatibility in larger and more diverse animal models.

Even so, the study opens a compelling new avenue for treating blindness through nanotechnology and optical engineering, one that, if successful, could be adapted for other forms of sensory or neural stimulation-broadening its potential impact across medicine and neuroscience.

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