See the number? (Image: Annabella Bluesky/SPL)

Glasses developed to help doctors spot veins more easily have a useful side effect – they enhance the ability to see reds and greens.

The glasses, made by 2AI Labs in Boise, Idaho, use filters to enhance perception of blood oxygen levels in vessels under the skin. But the filters happen to concentrate their effects around the wavelengths where red-green colour blind people are deficient. “We didn’t design them for colour blind people,” says Mark Changizi, of 2AI Labs, “but we weren’t too surprised to find they help.”

Daniel Bor, a red-green colour blind neuroscientist at the University of Sussex in Brighton, UK, experimented with the specs after Changizi asked for testers on Twitter. “They made my daughter’s lips and her red-orange jumper really stand out,” he said.


The spectacles helped Bor ace the Ishihara test, the standard test for red-green colour blindness, but he didn’t do so well on another test focusing on the entire colour spectrum.

Most cases of red-green colour blindness are genetic, so glasses like this correct rather than cure, and amplify reds and greens at the expense of discerning yellows and blues. “I couldn’t tell if the yellow light on my daughter’s baby monitor was on or off,” says Bor.

Changizi has suggested that primate colour vision evolved to help detect blood oxygen levels and so help sense health and emotion. The glasses were developed to enhance this ability and different versions are currently being tested by doctors to help spot bruising, and by poker players to help detect the subdued blushes of bluffing opponents.