EXPERT REACTION: New laser technique tricks the eye into seeing a never-before-seen colour

Media release

Five people have seen a color never before visible to the naked human eye, thanks to a new retinal stimulation technique called Oz. In a proof-of-concept experiment, Oz overcame the retina’s natural limits, activating thousands of retinal cone cells to reveal a highly saturated blue-green color. “Oz represents a new class of experimental platform for vision science and neuroscience, which strives for complete control of the first neural layer to the brain,” James Fongand colleagues write. Today’s color reproduction techniques manipulate light spectra to activate retinal cone cells. However, these cells overlap in their response to select wavelengths and intensities, limiting which colors humans can see. Now, James Fongand colleagues have developed a way to overcome this limitation. Their approach centers around spatial metamerism, which controls the spatial distribution of light on the retina rather than the spectra of light itself. Analyses of retinal cells showed that this strategy, called Oz, affects photoreceptor behavior and enables selective induction of M cone cell activity. Fong et al. built an Oz laser system that delivered light from cell to cell in 5 people. This process triggered M cone cell activity leading people to see color described as “blue-green of unprecedented saturation.” Oz also produced this color in videos and images viewed by the participants. The authors suggest their Oz approach could one day be used to improve color vision in those with colorblindness.