People with severe vision loss have been able to read again, thanks to a tiny wireless chip implanted in one of their eyes and a pair of high-tech glasses.

Age-related macular degeneration (AMD) is a common condition that affects the middle part of someone’s vision, often worsening over time. Its exact cause is unknown, but it occurs when light-sensitive photoreceptor cells and neurons in the centre of the retina become damaged, making it hard to recognise faces or read. Approved treatments can only slow its progression.

An advanced stage of AMD is known as geographic atrophy, but even here, people usually retain some photoreceptor cells that allow for peripheral vision and enough retinal neurons to pass visual information to the brain.

Taking advantage of this, at Stanford University in California and his colleagues have developed a device called PRIMA. It involves a small camera mounted on a pair of glasses that captures images, then projects them via infrared light to a 2-by-2-millimetre solar-powered, wireless chip implanted in the back of the eye.

The chip then converts the image information into an electrical signal that retinal neurons can pass to the brain. Infrared light is used because we can’t see in this wavelength, so the process doesn’t interfere with any existing vision. “This means patients can use both prosthetic and peripheral vision simultaneously,” says Palanker.

To put it to the test, the researchers recruited 32 people aged 60 or older who had geographic atrophy. Their vision in at least one eye was worse than 20/320, which means they could only see at 20 feet (6 metres) what a person with 20/20 vision could see at 320 feet (97.5 metres).

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The researchers first implanted the chip in the eyes of one of the participants, then, four to five weeks later, the volunteers began to use the glasses in their daily lives. The glasses allowed them to magnify what they were seeing by up to 12 times and to adjust the brightness and contrast.

After a year, 27 of the participants could read again, as well as perceive shapes and patterns. They could also see an additional five lines, on average, on a standard eye test chart, compared with what they could discern at the start of the study. Some could even read with the equivalent of 20/42 vision.

“When you watch them starting to read letters and then words, it’s an increasing joy on both sides. I recollect one patient telling me: ‘I thought my eyes were dead and now they are alive again’,” says team member at the University of Pittsburgh School of Medicine in Pennsylvania.

There are indications that stem cell implants or could help restore sight lost due to AMD, but these are still at early experimental stages. By giving the trial participants the ability to perceive shapes and patterns, PRIMA represents the first eye prosthesis to restore functional sight in people with the condition.

About two-thirds of the volunteers experienced short-term side effects as a result of the implant, including high pressure in the eye, but this didn’t prevent vision improvements.

“This is an exciting and significant study,” says at Imperial College London. “It gives hope for providing vision in patients for whom this was more science fiction than reality.”

The boosted vision the participants experienced is in black and white. “Our next goal is to add the software that will help resolve grey scales and enhance them for face recognition,” says Palanker. The researchers don’t expect to be providing colour vision any time soon, though.

Palanker also plans to boost PRIMA’s resolution, which is limited by the size of pixels affecting the number that can fit on the chip. He has been testing a more advanced version in rats. “This would correspond to a visual acuity of 20/80 in people, and with electronic zoom, we can go all the way to 20/20,” he says.

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Five people have witnessed an intense green-blue colour that has never been seen by humans before, thanks to a device that might one day enable those with a type of colour blindness to experience typical vision.

We perceive colour via the retina at the back of the eye, which typically contains three types of light-detecting cone cells – called S, M and L – that absorb a range of blue, green or red light, respectively, and then send signals to the brain. When we see anything at the blue-green end of the visible spectrum, at least two types of cone cells are activated at the same time because there is some overlap in the wavelengths they detect.

at the University of California, Berkeley, wondered what colour people would perceive if only one type of cone was activated in this part of the spectrum. He was inspired by a device called Oz, developed by other researchers studying how the eye works, that uses a laser capable of stimulating single cone cells.

Ng and his colleagues, including the scientists who built Oz, upgraded the device so that it could deliver light to a small square patch of about 1000 cone cells in the retina. Stimulating a single cone cell doesn’t generate enough of a signal to induce colour perception, says Ng.

The researchers tested the upgraded version on five people, stimulating only the M cones in this small area of one eye, while the other was closed. The participants said they saw a blue-green colour, which the researchers have called olo, that was more intense than any they had seen before. “It’s hard to describe; it’s very brilliant,” says Ng, who has also seen olo.

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To verify these results, the participants took a colour-matching test. Each viewed olo and a second colour that they could tune via a dial to any shade on the standard visible spectrum, until it matched olo as closely as possible. They all dialled until it was an intense teal colour, which supports them seeing olo as they described.

In another part of the experiment, the participants used a dial to add white light to either olo or a vivid teal until they matched even closer. All the participants diluted olo, which supports it being the more intense of the two shades.

at University College London describes the research as “kind of fun”, but with potential medical implications. For instance, the device could one day enable people with red-green colour blindness, who find it hard to distinguish between these colours, to experience typical vision, he says. That is because the condition is sometimes caused by M and L cones both being activated by wavelengths of light that are very similar. Stimulating one over the other could enable people to see a wider range of shades, though this needs to be tested in trials, says Stockman.