Blind mice were granted the ability to see in a recent experiment that could guide medical research toward greatly improved vision in blind human beings. In nature, animals such as snakes assess their surroundings by sensing both infrared radiation and the visible light spectrum. That’s clever on the reptiles’ part, but regrettably, humans do not have this superpower, because their eyes lack photoreceptors responsive to the infrared spectrum. And infrared light, with its longer wavelength and lower energy, cannot trigger typical visual signals in people. But if the visually impaired could be granted the strength of infrared vision, those with severe eye diseases could experience improved sight in low light and darkness — and they could see how they run.

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Courtesy of iStock.com/macy75.

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Some scientists have combated poor vision in the past using broad-spectrum retinal prostheses that use nanoparticles or photodiodes to convert infrared into visible light or heat to stimulate retinal cells. Unfortunately, in hindsight, these designs have required injections or bulky auxiliary devices, which means they cannot safely or practically help guide patients in everyday life.

Fortunately, a research team composed of scientists from Fudan University, the Shanghai Institute of Technical Physics, the Beijing University of Posts and Telecommunications, and Shaoxin Laboratory — all in China — designed a retinal nanoprosthesis based on tellurium nanowire networks that convert broadband light, including visible to infrared light, using photovoltaic conversion. Tellurium optoelectronic nanodevices were used in the experiment because they exhibited high photocurrents and the widest spectrum of responsive wavelengths reported to restore photosensitivity in blindness in previously published work.

Even before implanting the prosthesis, tests confirmed the stability of its optoelectronic properties and its preciseresponse to light patterns. This allowed scientists to observe how the nanowires operate — they naturally convert light into photocurrent signals with zero electrical interference, across the visible to the infrared spectrum. The tested nanoprosthesis generates strong photocurrents to activate the remaining retinal circuitry in a dysfunctional eye. It works via a simple subretinal implantation procedure, thereby avoiding bulky intraocular and extraocular components in the device.

To test their new technology, the researchers implanted their prototype into the subretinal space of mice and the primate Macaca fascicularis, also known as the crab-eating macaque. Once implanted in blind mice, the nanoprosthesis effectively replaced damaged photoreceptors and triggered responses in both the optic nerve and visual cortex. Implanted mice showed better light-induced pupil reactions and improvement in light-associated learning behaviors compared with untreated mice. And they didn’t even have to run from the farmer’s wife.

The biocompatibility and effectiveness of the prototype were also demonstrated in the macaque, where the nanoprosthesis was tightly bound to the retina in the subretinal space and generated retina-derived responses to visible and infrared light. The macaques implanted with this nanoprosthesis gained the benefit of infrared vision without impairment of their normal vision.

Based on the results seen in primates and mice, the potential for future human trials is real. Researchers hope that this prosthesis will not only restore vision but also expand augmented infrared perception for blind humans, offering a safer, more effective solution than anything seen or as yet unseen, on the market.

The research was published in Science (www.doi.org/10.1126/science.adu2987).