Colour blindness can be difficult to detect, particularly in children with inherited colour vision deficiency as they may be unaware that they have any problems with their colour vision. A child with a severe condition such as deuteranopia may seemingly be able to accurately identify colours which they can’t see (e.g. red) because they have been taught the colour of objects from an early age and will know for example that grass is green and strawberries are red even if they have no concept of their true colours.
You should see your GP if you have any problems seeing colours. Your GP will ask about your symptoms and examine you. He or she may also ask about your medical history.
There are many tests available to measure colour vision defects but the most common is the Ishihara Plate test. This can test for red/green colour blindness but not blue colour blindness. This is the test most likely to be used for routine colour vision screening in schools or medicals.
This test is the most widely used for testing for red-green colour vision deficiency and contains 38 plates of circles created by irregular coloured dots in two or more colours. The plates will be put in front of you and you will be asked what number you can see on the plate. Some plates contain information which people with normal colour vision can see whilst others contain information that only people with colour blindness can see. If you make a certain amount of errors you will be diagnosed with colour blindness. Special Plate tests have been devised to diagnose young children who are not old enough to identify numbers. An example of Ishihara plates is shown in these extracts from Colorblind World.
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Spotting the Early Symptoms of Colour Vision Deficiency in Children
The main symptom of colour blindness is a difficulty in distinguishing colours or in making mistakes when identifying colours. If a child is suspected of being colour blind the main clues to look out for are:-
- using the wrong colours for an object – e.g. purple leaves on trees, particularly using dark colours inappropriately
- low attention span when colouring in work sheets
- denial of colour issues
- problems in identifying red or green colour pencils or any colour pencil with red or green in its composition. (e.g. purple, brown)
- identification of colour may be made worse by low level light, small areas of colour and colours of the same hue
- smelling food before eating
- excellent sense of smell
- excellent night vision
- sensitivity to bright lights
- reading issues with coloured pages or work sheets produced with colour on colour
- children may complain that their eyes or head hurt, if looking at something red on a green background, or vice versa
- Colour blind children may not like to colour in pictures or want to play counting or sorting games with coloured blocks or beads.
If you think your child might be colour blind don’t waste any time in finding out if they are. You should immediately be suspicious if there are any colour blind men on the mother’s side of the family – these could be uncles, great uncles, cousins and grandfathers. By age 5 children with normal colour vision will be able to identify all of the groups of colours in a couple of seconds, but a colour blind child may also appear to be able to do this.
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. Use mid range shades, not too pale or too dark– and shade an area of about 2cm by 2cm of each colour onto the paper. 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 on the sheet. Do not show them each colour individually, they must be able to see all of the colours at the same time.
If your child shows signs that they are not sure whether a colour is red, green, brown, purple, blue or grey, there is a reasonable chance that they are red/green colour blind. You should expect a red/green colour blind child to be able to identify bright orange, yellow and pink (they can identify these colours by brightness and shade). Make sure you include these colours so that they do not get the impression that they are too stupid for the game.
Praise your child for identifying colours correctly and make sure that they know that there are no right and wrong answers. Also ensure that there are no other people around, especially siblings. If you are suspicious that your child might be colour blind, whatever you do, DO NOT follow up this exercise by questioning them about colours of items around the house. If you do this they may clam up and will certainly start to feel lacking in self-worth.
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 help.
There is hope on the horizon for a ‘cure’ for inherited colour vision deficiency using gene technology. This will involve injecting genetic material into the eye so is not for the faint-hearted! At the moment there have been no trials on humans but the process has been proved to work in monkeys.
For acquired colour vision deficiency, once the cause has been established and treated, your vision may return to normal.
For more information please call us or visit
McKenna & Scott Exclusive Optometrists in Pinelands.
Tel: 021 531 1953