Colour blindness

What is colour blindness?

There are several forms of colour blindness. The most common form is red/green colour blindness, which involves the confusion of red and green. It's passed on through a faulty colour vision gene on an X chromosome as a recessive disorder, so shows up more commonly in men but often carried silently by women. It has two forms:

• Different shades of red appear dull and indistinct
• Greens, oranges, pale reds and browns all appear as the same hue, distinguished only by their intensity

In one rare form of colour blindness, blues and yellows can't be distinguished. In another, all colours are seen in black and white.
Vision itself isn't affected, only the ability to distinguish between certain colours.

The Ishihara test

There are many different Ishihara test plates with coloured dot patterns. In this one, the image on the right shows a background of green dots with two wavy lines made up of red and orange dots. If you're colour blind, you won't be able to see these colours and so you won't be able to pick out the pattern from the dots.
This is the most common test used to diagnose colour blindness, but there are others such as versions that uses one colour of dots to spell out numbers that can be read by someone with normal vision, while colour blind people only see a random pattern.

Causes and risk factors

The retina of the eye has colour-detecting vision cells, called cones, which are necessary to see colour properly. There are three types of cone cell, sensitive to red, blue, or green light. If one or more of these types of cells is faulty, then colour blindness results.
Sometimes colour blindness occurs because of diseases such as macular degeneration or from side effects of medicines.
Stop signsColour blindness needn't stop someone driving, because traffic lights can be distinguished by the position of the light. However, it can be an obstacle to particular careers where good colour vision is important, including pilots, electricians, train drivers and some jobs in the printing, fashion and design industries.
You can't stop colour blindness if it's inherited, but if it's caused by underlying eye disorders or medication then it can sometimes be treated and stopped.
If you have always been colour-blind, it isn't necessary to see a doctor unless other eye problems, for example blurred vision, are occurring. However if your vision has changed and you are noticing colour loss or changes you need to get your vision checked. It isn't necessary to see a doctor unless other eye problems, for example blurred vision, are occurring.

Treatment and recovery

As inherited forms of colour blindness are harmless, no treatment is needed, even if it were possible.
READMORE: http://www.bbc.co.uk/health