What Is Colour Blindness?
Colour blindness is a recessive genetic condition carried through on the X chromosome, which leaves a person unable to see the normal spectrum of colours. It affects men more commonly as they only have one X chromosome. Women need to inherit the gene from both parents to be affected; however, women can often be 'silent' carriers.
Colour blindness does not affect the vision, it only changes the way a person sees colour. There three types of inherited of colour blindness:
- Monochromacy - this is when a person is unable to see colour at all. Both the rods and cones that pick up colour are unable to do so. As a result, vision is reduced to one dimension. When only the rods can see colour it is known as Rod Monochromacy, this condition is often associated with poor vision, and when only the cones can see colour it is known as Cone Monochromacy, this condition is associated with normal vision.
- Dichromacy - this is where one of the three primary colours cannot be seen. Colour is reduced to two dimensions. Protanopia is when the red photoreceptors do not function. Deuteranopia is when the green photoreceptors do not function. Tritanopia is when the blue photoreceptors do not function.
- Trichromacy - this condition is the most common and when the ability to see one of the primary colours is impaired or damaged. Protanomaly is when the red receptors are not functioning properly. Deuteranomaly is when the green receptors are not functioning properly; this deficiency is the most common of all. Trianomaly is when the blue receptors are not functioning properly.
To test whether a person has colour blindness, and what type they have, the Ishihara test is used. The test involves the patient being shown a picture made up of hundreds of random dots. To someone that can see normally, the dots form a picture of a simple shape, letter or number. Depending on what the patient can or cannot see will determine the condition they have.
Hereditary colour blindness is not harmful and a person can lead a normal life. In 2009, scientists published studies that showed they were getting closer to finding a genetic cure for colour blindness after they were able to restore full colour vision to adult monkeys born without the ability to see the difference between green and red. Studies were ongoing.
If colour blindness comes on over time, there may be an underlying problem that needs attention. It is important to see an optician at least every two years to insure the continuing health of your eyes Tweet