Researchers at the University of California, Berkeley, have developed a groundbreaking technology that can control up to 1,000 individual photoreceptors in the human eye at once. Dubbed “Oz”, this platform not only allows scientists to explore the intricacies of sight with unparalleled precision but has also enabled the creation of an entirely new color, a dazzling blue-green hue so vivid and saturated that it has been given its own name: “olo.”
Inspired by the dazzling illusions of the Emerald City in The Wonderful Wizard of Oz, this new frontier of vision science merges optics, neuroscience, and imagination in a way that’s as visually spectacular as it is scientifically profound.
The Oz system is as intricate as it is visionary. Built over several years by a multidisciplinary team at UC Berkeley, the platform uses highly precise laser pulses to stimulate specific cone cells—those responsible for detecting light and color—in the human retina. Normally, our eyes interpret color through the combined input of three types of cone cells: S (short wavelengths for blue), M (medium wavelengths for green), and L (long wavelengths for red). However, due to overlapping sensitivities between the M and L cones, isolating their signals has been nearly impossible—until now.
“We’ve created a system that can track, target, and stimulate photoreceptor cells with such high precision that we can now answer very basic, but also very thought-provoking, questions about the nature of human color vision,” said James Carl Fong, a UC Berkeley doctoral student and co-creator of the system.
The Oz platform was named deliberately, with Fong explaining, “It was like we were going on a journey to the land of Oz to see this brilliant color that we’d never seen before.” This journey has yielded its first spectacular treasure: “olo,” a color unlike anything seen in the natural world. By stimulating only the M cone cells—something that no natural wavelength of light can do—researchers created a uniquely saturated teal that even seasoned vision scientists were astonished by.
“It was like a profoundly saturated teal … the most saturated natural color was just pale by comparison,” said Austin Roorda, a professor of optometry and co-creator of Oz.
To produce olo, researchers first map the arrangement of cone cells in an individual’s retina. Collaborating with experts at the University of Washington, they use a specialized imaging system to chart each cone. Then, Oz scans a green laser across the retina, precisely pulsing only at the cones it wants to activate. Though the laser itself is a single color, the targeted stimulation of specific cone combinations allows the system to “paint” with light, effectively creating colors, including new ones like olo—directly in the brain.
The experience is immersive, even if the visual field is small, roughly the size of a fingernail held at arm’s length. “But if we could, we would have filled the entire visual space like an IMAX,” said Roorda.
In human trials, participants—including Roorda and Oz co-creator Ren Ng—described olo as “peacock green” or “blue-green,” but noted that it was far more intense than anything they had seen before. The dramatic impact of the color was revealed further when the laser’s targeting was slightly misaligned—called “jittering”—which caused the perception of olo to vanish instantly. “The normal color of the laser almost looks like yellow because the difference is so stark,” noted Hannah Doyle, a doctoral student who conducted many of the experiments.
Beyond creating colors, Oz offers deep scientific promise. It is already being explored as a tool to simulate vision loss, allowing researchers to better understand diseases that affect the eye by mimicking lost cone function. It may also lead to new ways for people with color blindness to experience colors they currently cannot perceive. Future applications could even stretch into enabling tetrachromatic vision—a hypothetical form of sight involving four types of cones.
“We found that we can recreate a normal visual experience just by manipulating the cells, not by casting an image, but just by stimulating the photoreceptors,” said Roorda. “And we found that we can also expand that visual experience, which we did with olo.”
At the heart of the project is a profound question: Can the brain interpret entirely new sensory information? Roorda believes it can.
“I like to believe that it can. I think that the human brain is this remarkable organ that does a great job of making sense of inputs, existing or even new.”
