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.
If you have any eye test with an optometrist (a registered health professional who examines eyes, tests sight and dispenses glasses and contact lenses) they should test your colour vision as a matter of routine, but not all chains of opticians in the UK do this test routinely and with some you may have to request a colour vision test specifically and sometimes even pay for it as an extra.
You can also 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.
To see the entire document go to www.neitzvision.com
More sophisticated tests are also widely used to ascertain whether someone with a colour vision deficiency would be suitable for certain occupations. A Lantern test is one such test which is used to identify people not suitable to work as train drivers or in marine and aviation jobs or other occupations where the work requires the ability to accurately reading the colours of lights for safety reasons.
At www.colorvisiontesting.com you can find an initial test for colour blindness on the screen. www.toledo-bend.com/colorblind/Ishihara.asp also shows some Ishihara plates tests for online testing. Please note that these tests are for initial testing only and will not give an accurate formal diagnosis. If you suspect that you or your child might be colour blind please seek professional help from an optician.
If you are still unhappy and would like a more detailed diagnosis you can arrange to have a full colour vision test. Click here to follow the link to the Colour Vision Clinic at City University where professionals will be happy to carry out a full colour vision assessment for you. The assessment will cover 8 separate tests and you will be given a report summarising your condition which can be used to advise schools and employers. There is a modest charge (significantly reduced for children).