by Lucille Parker

It is a common misconception that if you are “colour-blind” you see the world in black and white and grey – not so. The unfortunate 8% of the population who suffer from this vision impairment (sometimes known as “Daltonism” after the physicist John Dalton, who was colour blind himself), can detect colours. They just don’t see them the way other people do. While this does not leave them unable to function in the real world, it does cause a whole lot of problems which they have to work around – and, there is no cure.

Colour-blindness is a hereditary condition – a recessive gene on the X-gender chromosome causes it. Women can carry the deficiency (without necessarily suffering colour-blindness themselves) and can pass it on to their sons. This is why more men experience colour-blindness than women.

The way it works is this:
The human eye works by light stimulating the retina, which is a neuro membrane lining the inside back of the eye. The retina is made up of rods and cones. The rods – found round the outer edge of the retina – give us the ability to see at night, and do not distinguish colour. The cones, in the centre of the retina (an area called the macula) are the cells responsible for letting us perceive colour in daylight conditions.

Each of the little cone cells contains a light sensitive pigment which picks up colours over a range of wavelengths. Genes contain the coding instructions for the pigments, so if the genes are wrongly coded in this respect, the pigments get a little screwed up and the cones will be picking up the wrong colours for the different wavelengths.

Seems this is one annoying hereditary trait that will only be “fixed” by genetic engineers in the future!

Fortunately it is very rare for a person to be totally colour-blind – this is a condition called “monochromasy” which is a complete absence of any colour sensation. There are, however, many different types and degrees of colour-blindness or colour vision deficiencies.

It is very important for any colour deficiency to be diagnosed early – not because the condition can be treated, but because a sufferer can be supported and assisted to learn to deal with the problem.

The most common deficiency is difficulty with differentiating the colours of green and red – a particular problem when it comes to “stop” and “go” buttons, and traffic signals, as you can imagine, not to mention danger signs!

  • One out of 100 men experience protanomaly - problems with perceiving red. These people see red more weakly than a normal viewer – the saturation, brightness and hue are affected and appear greenish to him, and pale. Red is a component of violet and purplish shades too, so he will have difficulty discerning these – they will all look like different shades of blue to him. In bad conditions, like fog or bright sunlight, a protanomaly sufferer could mistake a blinking red for a yellow or amber one.

  • Five out of 100 men experience deuteranomaly, which means they are “green weak” in the same way the protanomalous person is “red weak”. One difference though – they do not lose out on the brightness of the colours, only the hues in the red, orange, yellow and green spectrum.

    Note that many protanomalous and deuteranomolous men go through their whole lives not being aware their colour perceptions are “off” the norm. Usually they have mentally compensated and can function – even in colour-related tasks, quite normally.

  • Dichromasy is suffered by two out of 100 males and these guys definitely know they have a colour vision problem – it affects their lives daily. They can discern no difference between red, orange, yellow and green – all these colours appear the same to them. For some, reds look black or dark grey; pink flowers can look blue or grey – there are a whole range of kinds and degrees of deficiencies, based mainly on the fact that sufferers experience different degrees of “dimming” of the colours mentioned.

    Imagine how strange it must be for a pre-schooler being taught colours – he must wonder why everyone around him can happily call red, orange, yellow and green by different names, but they all look the same to him! The same is true for violet, lavender, purple, and blue. Among the colours most often confused are pink/grey, orange/red, white/green, green/brown, blue green/grey, green/yellow, brown/maroon, and beige/green. Pastels and muted tones are difficult to distinguish. The colour vision defect may be so bad that the affected person cannot distinguish brown from black shoes, a red traffic light from an amber one, or green grass from brown soil by colour alone.

    It is all very confusing and inconvenient, although sufferers say it is not all bad! Read what one colour-blind man has to say:
    “Colour blindness does have some advantages. We look for outlines, not colours, so we don't get easily confused by camouflage (colour blind people were used in World War II spy planes to spot camouflaged German camps). Our night vision tends to be much better than average. Also, we're banned from jobs such as the police, fire brigade, medical profession or being a pilot (well, not getting shot at, burned, badly paid or smashed into a mountain sounds like an advantage to me).”

    With such a high proportion of the population suffering from colour-blindness, it is strange that society does not take more notice of the condition: think of all the machines that tell us to “press the red button”; all the environments with green safety lights, red warning lights – what about colour-coded tablets. Even cell phone chargers work with red and green lights. Websites on the Internet are a minefield for colour-blind individuals. Then how about matching your clothes when you get dressed, not to mention telling the difference between a dollop of tomato sauce or chocolate sauce in the kitchen! Reading maps can be a problem, and even complimenting your girlfriend on the shade of her lipstick.

    Most sufferers describe these as minor irritations that can be overcome with ingenuity and experience of the condition – a small child, though, can be emotionally damaged by undiagnosed colour-blindness, because teachers and peers may regard his inability to perceive colours (choose the right crayon for example) as a learning disability or simply being “dumb”!

    CLICK HERE to take an online test to check whether you are seeing the world in all its colourful glory!

    Mail reader response to: Lucille Parker, iafrica.com Feature Writer.


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