UC Berkeley scientists created a new platform called “Oz” that directly controls up to 1,000 photoreceptors in the eye at once, providing new insight into the nature of human sight and vision loss. In this photo, Oz creator Austin Roorda, a professor of optometry and vision science at UC Berkeley, demonstrates what it looks like to be part of the Oz experiment. (Credit: UC Berkeley)
In a nutshell
- UC Berkeley scientists created “olo,” a never-before-seen color that exists beyond the natural human vision range by precisely targeting individual photoreceptor cells in the eye.
- The technology, called “Oz,” bypasses natural vision limitations by activating only M-type cone cells in isolation, which never happens with natural light.
- Participants described olo as an intensely saturated blue-green that required adding white light before it could be matched with conventional colors, proving it exists outside our natural color gamut.
BERKELEY, Calif — Scientists at UC Berkeley have achieved the seemingly impossible — they’ve created a color that lies beyond the natural range of human vision. This unprecedented color, dubbed “olo,” appears as an intensely saturated blue-green unlike anything people have ever seen.
The breakthrough comes from a new technology and principle called “Oz,” which allows researchers to precisely stimulate individual photoreceptor cells in the human eye — bypassing the natural constraints that normally limit our perception of color.
Subjects in the study reported perceiving “blue-green of unprecedented saturation,” a color signal that doesn’t naturally occur in human vision because it results from stimulating only one type of cone cell, a feat previously thought impossible.
The human eye contains three types of cone cells — L (long), M (medium), and S (short) — each sensitive to different wavelengths of light. Our brain creates the experience of color by interpreting the combined activity of these cones. However, because their sensitivities overlap, no single type of cone is ever activated in complete isolation under normal conditions.
This overlap imposes a fundamental limit on the range of colors we can see. But what if we could stimulate just one kind of cone at a time?
Breaking the Color Barrier
The research team answered that question by developing a sophisticated system that uses adaptive optics and high-speed laser pulses to stimulate individual cone cells. After mapping and classifying thousands of cone cells in participants’ retinas, the team used their Oz prototype to precisely target M-cones — and only M-cones — with light.
“There’s no wavelength in the world that can stimulate only the M cone,” said study senior author Ren Ng, a professor at Berkeley, in a statement. “I began wondering what it would look like if you could just stimulate all the M cone cells. Would it be like the greenest green you’ve ever seen?”
Over 200 color-matching experiments with five participants revealed something remarkable: when only M-cones were stimulated, participants saw a vivid, unfamiliar blue-green color they could not reproduce using conventional light sources.
“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 vision science at UC Berkeley’s Herbert Wertheim School of Optometry & Vision Science, and one of the creators of Oz.
To confirm that this new color, “olo,” truly lies outside the natural range of vision, participants were asked to match it using traditional methods. They could only do so by adding white light to dilute it — a strong indicator that olo exists beyond the natural human color gamut.
Future Implications
The current version of the Oz system works only in a small area of the retina, just off the center of gaze, and requires participants to fixate steadily. Expanding the system to allow free eye movement or cover larger parts of the visual field would require mapping many more cone cells and greatly increasing the system’s processing power.
Even so, this research, published in Science Advances, marks a fundamental advance in the science of vision. By controlling individual photoreceptors in real time, scientists have created an entirely new category of visual experience — a glimpse into colors that, until now, were only theoretical.
Paper Summary
Methodology
Researchers developed a system called “Oz” that can stimulate individual photoreceptor cells in the human retina with unprecedented precision. First, they used adaptive optics optical coherence tomography to spectrally classify 1,000-2,000 cone cells in each subject’s retina according to type (L, M, or S). Then, using adaptive optics scanning laser ophthalmoscopy, they tracked eye movements in real-time with infrared light while delivering precisely targeted visible-wavelength laser microdoses to specific cone cells. The system delivered about 100,000 microdoses per second to a population of about 1,000 cones in a 0.9° square field of view, positioned 4° away from the subject’s gaze fixation point.
Results
Five subjects participated in 222 color matching experiments using two different stimulation wavelengths (488nm and 543nm). When researchers attempted to activate only M cone cells using the Oz system, subjects perceived a color they named “olo” that appeared as a highly saturated blue-green. Formal color matching experiments confirmed that this color lies beyond the natural human color gamut – subjects needed to add white light to desaturate olo before they could match it with conventional colors. The researchers also showed that subjects could recognize images and videos rendered in Oz colors, including red lines and moving dots on an olo background. When researchers deliberately compromised the precision of the targeting by randomly “jittering” the microdoses to incorrect neighboring cells, subjects’ performance dropped to guessing level, confirming that accurate targeting is essential.
Limitations
The current system has significant practical limitations. It works only over a small 0.9° square visual field positioned 4° away from the subject’s fixation point, requiring subjects to maintain gaze on a fixed target. Expanding this to allow free eye movement or cover larger visual areas would require mapping much larger retinal areas and substantially increasing computational power. The current cone classification technique has progressed to within 0.3° of the fovea (central vision) but cannot yet map the smallest cells at the very center of vision.
Funding/Disclosures
The research was supported by multiple grants, including a Hellman Fellowship, FHL Vive Center Seed Grant, Air Force Office of Scientific Research grants, National Institutes of Health grants, and a Burroughs Wellcome Fund Career Award. The Regents of the University of California have filed a patent for cell-by-cell retina stimulation, with several of the researchers listed as inventors.
Publication Information
The paper, titled “Novel color via stimulation of individual photoreceptors at population scale,” was published in Science Advances on April 18, 2025. The lead authors are James Fong, Hannah K. Doyle, and Congli Wang, with corresponding author Ren Ng from the Department of Electrical Engineering & Computer Sciences at the University of California, Berkeley.
