• Question: how do people go colourblind?

    Asked by roisin333 to Enda, Jean, Kate, Kev, Tim on 19 Nov 2012.
    • Photo: Jean Bourke

      Jean Bourke answered on 19 Nov 2012:

      We are able to see because of specialised photoreceptor cells in our eyes. These detect light and then signal our brain which forms the complete picture. There are 2 main types: rod cells and cone cells (rods and cones). Rods do not need a lot of light to function and mainly detect light being there. Cones are the ones that allow us to see colours. There are 3 different kinds detecting different colours of light (the colour corresponds to the wavelength). There is a bit of overlap but the are referred to as red, green, and blue.

      Total colourblindness means you cannot distinguish any colours. But you can be partially colourblind too, being unable to see or distinguish other colours.

      Colour blindness is due to cone cells being damaged or defective, it can be genetic or due to disease such as macular degeneration and diabetes (which can damage the eyes). UV light can also damage your eyes but usually colour blindness develops over time. Vitamin A deficiency can also effect colour blindness.

      One way to get around colour blindness involves a machine called an eyeborg which links colous to sounds.

    • Photo: Enda O'Connell

      Enda O'Connell answered on 19 Nov 2012:

      Hi Roisin333,

      I heard a scientist speak at a conference once about a type of experiment called Microarrays, that I do from time to time. The experiment involves labelling one sample (let’s say tissue from a healthy person) with a green dye and the other sample (let’s say some tissue from a biopsy, where the patient may have cancer) with a red dye. The two samples are mixed together and it allows you to look at which genes are different between the two different samples, so you can make a diagnosis and perhaps suggest a treatment. When you analyse the genes on a computer, they are normally coloured green and red, to help you tell which sample is which.

      The interesting thing about the talk (apart from the science, of course) is that the scientist speaking never realised he was red-green colour blind before he started working with microarrays. When he looked at the results they all looked the same to him, while his colleagues noticed huge differences between the red and green coloured samples. Now, when people work with microarrays they often use blue and yellow to differentiate between the samples on a computer screen, even though they still use the red and green dyes in the lab.

      In some cases however colour blindness may be an advantage, as it has been shown to enable capuchin monkeys see through certain insect camouflages, which is of great benefit as they get to eat more insects!

      There are even stories of colour blind soldiers being in demand in the Second World War as camouflage spotters, but I couldn’t find any evidence of this (although I did find out there was a band called Colorblind Soldiers – Google is great) and certain vision impairments restrict people from some military jobs so it might be an urban legend.

      This advantage in certain cases may explain why red-green colour blindness is so common affecting between 7 and 10% of men. It is much less frequent in women because the important genes are found on the X chromosome. If one of the genes becomes mutated in women they have a backup X chromosome with a functioning gene, while us poor unfortunate men have only one X chromosome along with a troublesome Y…