Saturday, 16 July 2016

Science Progresses - Glasses for the Colourblind

If you know of anyone in your life who is red-green colour blind, have a look at this. I had a student last year who was in my remedial mathematics class ... until he started wearing a similar product. He was out of my class in two months. This video is from a brand called EnChroma glasses, and the story and science behind their development is fascinating.
So firstly, these glasses predominantly treat red-green colour blindness. The colour receptors for red, green and blue light are controlled by single genes in our DNA, and there is large variation in their frequency response in the human population. Basically some people see darker reds as "red" and some people see yellower reds as "red", and similarly for greens. Everyone's colour experience is a little different. However, if someone's genes for the red receptor and the green receptor overlap too much, the brain never learns to distinguish between a "red" signal and a "green" signal. Each colour receptor helps distinguish about 100 shades, so a red-green dichromat (only sees two primary colours) has a colour vision 100 times LESS powerful than others.
These glasses absorb a very narrow frequency of light in the yellow part of the spectrum, "splitting" the red and green signals in the eye/brain, helping people to distinguish between reds and greens.
They were originally developed for surgeons to help them to see veins and connective tissue amongst red tissue and blood during surgery. One day, a red-green dichromat tried on his surgeon friend's glasses out of curiosity and "holy crap, I can see more colours." What's fascinating is that the brain adapts to the new signal almost immediately.
What's doubly (hah, you'll get the pun in a minute) fascinating is that the gene for the red colour receptor is on the X chromosome, which is why red-green dichromats are predominantly male. They only get one version of the X chromosome, and if they get a dud red-receptor gene, they're screwed.
But women get two X chromosomes, and if a woman gets two immensely different red-receptor genes (officially referred to as a tetrachromat), she may see colours MORE intensely than the average human.
Now here's the final kicker. Mice, like a lot of nocternal mammals, are naturally dichromat. Some time in their evolutionary past, they lost a gene that gives trichromatic vision. But scientists have genetically engineered adult mice to turn that gene back on, effectively giving mice full (well full human) colour vision. The mice's brain's had no trouble interpreting that new colour channel, which is really fascinating, because if colour interpretation relied on fixed brain structures, mice have been dichromatically colour blind for long enough that evolution could have removed or damaged those structures.
This suggests to me (note that I don't have any references or research for this final conclusion, it's purely a hypothesis by a science teacher) that the brain colour processing systems of mammals are flexible enough to handle loss and gain of colour channels without rewiring. Imagine targetted genetic therapy to add other colour receptors to the human eye.
Now, who wants to see in Infrared?

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