Five people have seen a color never before perceived by the human eye a bluish-green one called “olo” that is beyond the boundaries of human sight. The achievement is the result of a precision experiment in which scientists selectively activated certain cone cells in the retina with laser microdoses. The outcome? A “jaw-dropping” and “incredibly saturated” color, according to Ren Ng, a University of California, Berkeley electrical engineer, and also a member of the research team.
Human color vision relies on three types of cone cells in the retina: S cones for short wavelengths (blue), M cones for medium wavelengths (green), and L cones sensitive to long wavelengths (red). The cones function in overlapping ranges so that light exciting M cones will excite adjacent S or L cones. This overlap has long been accepted as an unavoidable shortcoming of human vision. But Ng and his coauthors were curious about what would happen if M cones were excited by themselves. To test this, they employed a method called “Oz,” named after the blindingly green of the Emerald City in L.
Frank Baum’s books, the researchers mapped the retina of each subject to find exactly where his M cones were. Using adaptive optics optical coherence tomography (AO-OCT), they type-classified the types of cones by observing how their shape changed when exposed to specific wavelengths of light. Having them mapped, the scientists used lasers to send precise pulses of light to M cones alone, avoiding the typical overlap that occurs. The result was breathtaking.
Volunteers reported seeing a color unlike anything previously seen. Ng called it “blue-green with unmatched saturation,” and stated that even the most saturated teal viewed under ordinary vision has no match. Volunteers were made to take color-matching tests in order to check the findings, varying the saturation of a typical teal until equivalent to olo. They continually discovered that olo needed white light added to it in order to desaturate it, proving its intensity outside of the natural spectrum. The applications of this study reach much further than the development of new colors. The Oz procedure might be used to assist color-blind individuals, who are likely to have overlapping excitation of M and L cones. Through selective stimulation of single cones, scientists might even be able to enable color blind people to see colors they can’t see today. But Ng warns that even this would only be a temporary experience, not a cure.
Aside from medical uses, the technology also poses intriguing potential in research into vision perception. The research was named a “truly groundbreaking advance” by Manuel Spitschan, a researcher at the Max Planck Institute for Biological Cybernetics, studying how animals perceive color. The method has potential to apply to simulating animal color vision as well as enabling humans to see the world through the eyes of a dog, mouse, or goldfish.
While exciting, the Oz system also has very serious drawbacks. It only currently stimulates an area of approximately twice the area of the Moon in the sky and demands that test subjects maintain fixation on a point. To have the method treat larger areas of the retina or allow for more free motion of the eyes would demand phenomenal levels of precision as well as cutting-edge technology.
Moreover, the equipment required is highly specialized, involving lasers, mirrors, and modulators that are unlikely to be adapted for consumer devices anytime soon. As Ng himself noted, “We’re not going to see olo on any smartphone displays or any TVs any time soon. And this is very, very far beyond VR headset technology,”
The finding of olo pushes the limits of humanity’s sight and challenges the nature of color itself. Is olo a new color or improved version of a color already in existence? Although some scholars, like John Barbur of City St George’s, University of London, describe olo as simply a greener and more saturated option, others assert it is a glimpse into uncharted sensory dimensions.
As Ng’s team continues to refine the Oz technique, the possibilities for future research are enormous. From investigating the brain’s contribution to the creation of visual experience to investigating cures for degenerative eye conditions such as retinitis pigmentosa, the technology has the potential to revolutionize our understanding of sight. Meanwhile, olo is a brief and rare glimpse into a new world of color an accomplishment that demonstrates the incredible power of science to push the boundaries of human experience.
