Spectacles that could cure a person’s colour blindness and allow them to see the full spectrum for the first time have been developed by scientists.
The high tech glasses help those with "red-green deficiency", an inability to see some red and green colours.
The genetic abnormality is estimated to affect about 10 per cent of all adult men and a small number of women.
The invention by 2AI Labs, an American research institute, has been produced based on years of research into how human sight has evolved, the Times reported.
The Labs reportedly developed several different pairs of glasses that could enhance the ability to see "oxygenated blood" in the skin.
Scientists originally thought the spectacles, which feature special "Oxy-Iso" lenses, could be used for medical purposes such as identifying veins before blood donation or identifying bruising.
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.