Could new hi-tech spectacles cure colour blindness? But they found that people with the "red-green" colour-blindness could also use them to fix their condition. "If you squeeze your hand in front of you and let go, you'll see these yellow spots where the blood has been squeezed out and reddishpurple spots where the blood is pooling," Mark Changizi, an evolutionary neurobiologist behind the project, told the Times. Those are changes in the concentration of the blood. In 2006, the author of Harnessed: How Language and Music Mimicked Nature and Transformed Ape to Man, suggested humans had evolved the ability to observe subtle changes in skin colour. "Most mammals - your dog, horse, bunny - have two dimensions of colour," he told another website. A yellow-blue dimension, and a grayscale (or brightness) dimension. Some of us primates, however, have an extra dimension of colour vision: The red-green dimension. Daniel Bor, from the University of Sussex, said the glasses allowed him to pass the so-called "Ishihara Colour Test," in which patients are shown plates that feature a circle of dots. Experts say those who are colour-blind cannot make out numbers within the dots. Glasses with Oxy-Iso lenses are already on sale, with a pair costing $279 (£178). But while the lenses enhance the ability to see reds and greens, they also downgrade the ability to see yellows and blues.