Colour Blindness

Colour vision is controlled by light-sensitive cells in your eyes known as cones. There are three types of cone cells, each containing photopigments that perceive either blue, green or red. Colour blindness occurs if one or more of these types of cones is missing or defective.  In most cases, colour blindness is genetic. However, this deficiency can also be triggered by damage to the eye, optic nerve or part of the brain that processes colour. Additionally, your ability to perceive colour can be affected by ageing, certain medications and conditions such as diabetes, Alzheimer’s disease and cataracts. 

There are several variations of colour blindness based on which cones are affected and to what degree. The most common form is red-green colour blindness, which occurs more often in men than women. A person will have red-green colour blindness if either their red or green cones don’t work properly or at all.   Another form of colour vision deficiency is blue-yellow colour blindness. Similar to the red-green variety but much less common, it’s characterized by faulty or absent blue cones. In very rare cases, total colour blindness or monochromacy occurs if all three types of cones are missing, which prevents the person from perceiving colour at all.

Common signs of colour blindness include difficulty or inability to distinguish between different colours or different shades and tones of the same colour. If someone is born with colour blindness, however, it’s often their parents or others around them who will first notice the condition. This usually occurs at a young age when the child is learning their colours.