We perceive color using information from the cones of the retina.
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In April, a team of researchers reported that the device allowed them observe intense green-blue color something people have never seen before. Since the announcement, they have been inundated with requests from the public to see the color with their own eyes.
The device could allow people with some types of color blindness to experience typical vision and even allow people with typical vision to perceive a wider range of hues. “We're very interested in expanding color perception,” says Austin Roorda at the University of Waterloo in Canada.
In most people, the retina at the back of the eye contains three types of cones called S, M and L, each of which detects light at a different range of wavelengths. Our brain creates our perception of color based on signals from these three types of cones.
The range of the visible spectrum detected by M cones overlaps that of the other two types, so we don't typically receive signals from just M cells.
Roorda and his colleagues used an extremely precise laser to activate about 300 million cones in a small square area of the retina. “This spot corresponds to a portion of the visual field equivalent to the size of a fingernail at arm's length,” says Roorda.
When the five researchers used the device, they saw a blue-green color more intense than anything they had seen before, which they called “olo.” This was confirmed using a color matching test in which they compared olo to the full range of shades in the visible spectrum.
“It was a really amazing moment,” says Roorda, who has seen Olo more times than anyone else thanks to his key role in developing the system. “The richest natural light looked pale by comparison.”
After the achievement made waves in the media, the team received dozens of requests from people – including artists – to view the olo. But it takes days to set up the system for a new person, so the team couldn't afford to accommodate them, says Roorda.
Instead, they focused on two ongoing experiments. First, they will test whether the device can allow people with color blindness to temporarily experience typical vision. Some types of color blindness are caused by having only two types of cones rather than three. “We'll play with some cones that are one type of cone a little differently than other cones of that type, and we think that will send signals to the brain as if they had a third type of cone,” says Roorda. The hope is that people's brains will interpret these signals as new colors they haven't previously perceived, he said.
The team is also studying whether a similar approach could allow people with three types of cones to perceive the world as if they had four, which some people naturally have, allowing them to see a wider range of colors. Results from both experiments should be available next year, Roorda says.
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