Scientists have designed a method to divert the human eye, which allows it to see new colors that are beyond the scope of natural human vision.
With this technique, the researchers allowed five people to see a new color, nicknamed “OLO”, which the participants in the study described as an “unprecedented saturation blue”. The researchers, some of which participated in the experience themselves, described their technique and the new color in a study published on Friday April 18 in the journal Scientific advances.
“The ultimate objective is to provide programmable control on each photoreceptor (light detection cell) in the retina”, mainly for research, said Co-Prime Author James FongA doctoral student in computer science at the University of California in Berkeley. “Although this has not been achieved at this level, the method we present in this study shows that many key principles are possible in practice,” Fong à Live Science told an email.
Control of the retina at this granular level could open new ways to study the vision, the researchers said. For example, scientists could use the system to reproduce the effects of different eye diseases to better understand the loss of vision they trigger. In theory, the technique could also be used to simulate a color vision in people who are in color crisis, essentially compensating for their missing or defective photoreceptors.
Using the system to introduce the brain of new visual data and models of retina stimulation, in theory, “it may be possible that this (blind) person learns to see the new dimension of color,” suggested Fong.
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Trip to oz
Human eyes Contain cells sensitive to light, called photoreceptors, which appear in two forms: rods and cones. The stems allow a night vision, because they react to relatively low levels of photons, or packages of electromagnetic radiation.
The cones take over in a bright light, and they specialize in detecting specific wavelengths of visible light – namely red, green and blue. These three types of cones are respectively named “L”, “M” and “S”, in reference to long, medium and short wavelengths of the visible spectrum to which they are the most sensitive.
Once the cones have been activated, the vision of colors rests on the brain Interpret the activation models of these three types of cells through the retina. Each pattern acts as a code, with different codes unlocking different perceptions of colors and intensities of light.
The M cones are the most sensitive to green, but technically, they react to a whole spectrum of colors that overlap completely with the L wavelengths and react. As such, under natural conditions, you cannot activate the M cones without also activating the L and S cones. Scientists wondered what would happen if you could challenge this rule and activate the M. cones exclusively
“We initially started this project specifically to study the stimulation of the cone M,” said Fong. “But it quickly became clear that (the required underlying technology would be largely useful for studying the visual function at a new level of scale and precision.”
They named their retinal stimulation technique which results in “Oz”, in tribute to the glasses tinged with green that the people of the city of Emerald carry in the original books “Wizard of Oz”. The approach requires a detailed card of the retina of each user. To create such a card, the researchers started by taking several videos of the retina and assembling them to capture what the fabric looked like.
From there, the L, M and S cones were labeled; The locations of these cells are unique in the retina of each person, noted FONG. To reveal the identity of each cone, the researchers used a technique called Tomography by adaptive optical coherence (AO-COT), which involved a bright light on the cells and measuring the way in which they changed the form; This answer differs according to the wavelengths to which a cone is sensitive.
With a detailed retinal card, the team then managed their experiences. Each participant was seated in front of a screen with a small square in its center, where Oz stimulation took place. Stimulation has targeted specific types of cones with visible laser light, called laser microdoses. Thus, to activate only the M cones, the system has only targeted cells with lasers.
Scientists also used a real -time eye flow during experience, and the approach took into account the subtle movement of the eye, to ensure that lasers reach their targets.
Reveal a new color
Stimulate only M cones revealed the OLO color, whose name refers to the coordinates on a 3D color card – “0, 1, 0.” The “O” is a zero, referring to the lack of stimulation of the L and S cones, while the “L” is a 1, indicating a complete stimulation of the M. cones After stimulating OLO in isolation, the scientists were also able to integrate the color in the images and the videos visualized by the participants.
One way to imagine Olo is to think of the light of a green laser pointer, then to go up the saturation. In comparison with Olo, monochromatic laser light seems “pale”, said certain participants. “It is very foreign to me to imagine how something else could be sufficiently saturated at the place where the laser begins to appear pale in comparison,” said Fong.
Although Oz can already push the limits of human vision, it has certain limits in its current configuration.
For example, participants cannot directly look at the OZ display, noted Fong, because the cones at the very center of the retina are very small, which makes the location of laser light difficult. For this reason, the people of the study saw Oz with their peripheral vision by looking at a fixed point slightly far from the square.
Finally, Oz could potentially be applied to the Fovéa – the central part of the retina which allows a super Sharp vision – but “it will be an important challenge in practice,” said Fong.
Another limitation is that, currently, users must repair their eyes in one place to use OZ, because scientists were up to a small part of the retina containing thousands of cones, as proof of concept. Allowing people to freely change their eyes would introduce “substantial technical challenges”, wrote the authors in their article. Indeed, a larger part of the retina should be mapped and that the method of delivery of microdoses should be extraordinarily precise to follow the movement of the eyes.
Scientists now explore the idea of using Oz to study and treat color blindness, as well as to stimulate the experience of having a fourth type of conical cell. This occurs naturally in some people and results in a rare capacity called tetrachromacitywhich strengthens their sensitivity to color. The team also uses Oz to model various eye diseases.
Apart from scientific research, Oz could theoretically be used for daily colors displays, such as those on your television or phone screen – but this application seems very improbable, said Fong.
“Our current method depends on lasers and highly specialized optics that certainly do not come to smartphones or televisions immediately,” he said. So, for the moment, Olo will remain a rare color seen by a few.