Colour blindness (colour vision deficiency, or CVD) affects approximately 1 in 12 men (8%) and 1 in 200 women in the world. There are different known causes of colour blindness. For the majority of people with deficient colour vision, the condition is mostly genetic and has been inherited. Most colour blind people are able to see things as clearly as other people but they are unable to fully ‘see’ red, green or blue light. There are different types of colour blindness and there are extremely rare cases where people are unable to see any colour at all.
CAUSES OF COLOUR BLINDNESS
In the retina, in the back of the eye, there are two types of cells that pick up light in any form. Rod cells see things at night, but don’t pick up colours. Cone cells pick up brighter light and see details and different types of colours.
There are three types of cone cells. Each type picks up a different colour –RED, GREEN AND BLUE. In a person who is colour blind, only two out of these three types of cone cells work normally. Children usually inherit colour blindness from either their mother, father or both parents.
Red-green colour blindness is the most common type. It happens in 8% of boys and 0.4% of girls. Blue colour blindness happens in only 5% of cases of colour blindness. It happens equally in boys and girls.
SYMPTOMS OF COLOUR BLINDNESS
- using the wrong colours for an object
- low attention span when colouring something
- Problems in identifying red or green colour pencils or any colour pencil with red or green in its composition.
- Smelling food before eating
- Excellent sense of smell
- Excellent night vision
- Sensitivity to bright lights
- Reading issues with coloured pages
- Children may complain that their eyes or head hurt, if looking at something red on a green background.
IDENTIFYING COLOUR BLINDNESS
If any of these symptoms are visible to your child then immediate medical help should be sought. To give yourself a basic indication of whether there might be a problem with your child’s colour vision, get a sheet of white paper and a set of colouring pencils – at least 12 different colours but including green, red, brown, orange, blue, purple and grey. Make sure that the colours are in a random order and you don’t have all the reds or greens together, but do place red, green and brown adjacent to each other.
Take the paper and your child to an area with good natural light (but not bright light, artificial light or strong sunlight) and make a game up which involves asking your child to identify all of the colours one by one. Do not show them each colour individually, they must be able to see all of the colours at the same time.
TREATMENT
There is currently no treatment for inherited colour blindness. Colour filters or contact lenses can be used in some situations to enhance the brightness between some colours and these are occasionally used in the workplace, but many colour blind people find these actually confuse them further rather than helping them out.