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Ever debated whether something is blue or green? Chances are, you could be colour blind.
People who experience colour blindness see a narrower range of colour.
While those with normal colour vision can detect 1 million distinct shades, colour blind individuals see only 1% of that spectrum.
BOTANICAL BLIND SPOTS
In 1688, British physicist and chemist Robert Boyle wrote about his maid collecting violets from their garden.
She distinguished the flowers from the weeds by shape and feeling because she was unable to see the difference in their colour.
A century later, another British chemist and physicist, John Dalton, observed his own and his brother’s visual deficiencies.
He published the first scientific paper on what is now known as red-green colour blindness.
The condition was nicknamed Daltonism in his honour.
WHEN CONES GO ROGUE
Daltonism stems from abnormalities in the cones – the photoreceptors within your eye that detect colour.
Credit: Cleveland Clinic
There are three types of cones (blue, green and red) that work together, communicating with your brain to interpret light wavelengths.
All forms of colour blindness occur due to missing or faulty photopigments within these cones – the pigments responsible for colour perception.
RED MEANS GO, RIGHT?
Red-green colour blindness, the most common form, is an umbrella term for deuteranopia and protanopia.
This condition causes an inability to discriminate colour in the red-green region of the light spectrum.
Blame it on the missing green (deutan) or red (protan) photopigments.
Red and green are no longer distinct colours but look quite similar.
Blue-yellow colour blindness, or tritanopia, is caused by the absence of blue photopigments.
Unlike red-green, which is genetic, this form is usually acquired later in life and caused by ageing of the eye or medical conditions like glaucoma.
For the very unlucky ones, there is achromatopsia – complete colour blindness.
Everything appears in shades of grey, black and white because of the lack of photopigments.
Caption: Depiction of how people with Deutan colour blindness perceive traffic lights
Credit: Enchroma
BOYS WILL BE … COLOUR BLIND?
Males are significantly more likely to experience red-green colour blindness, with 1 in 12 affected compared to 1 in 200 females.
Why?
It is a recessive genetic mutation passed down via the X chromosome.
Since males only have one X chromosome, this gene will always be expressed.
Females have two X chromosomes and can therefore be carriers of the gene and will not always express the mutation.
So the next time someone calls the grass blue, maybe cut them some slack.
They’re probably just colour blind.
