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  1. Centre for Applied Vision Research
School of Health Sciences

A new web-based colour vision test

Background

People with a serious fault or absence of "red," "green" or "blue" cones in the retina cannot tell the difference between certain colours.

The absence of one of these pigments makes people confuse some colours and this is described as "colour deficiency."

To diagnose colour deficiency, we need to ensure that the subject can only make use of colour signals. Other things like luminance contrast must be eliminated, and this is not always easy. At City, University of London (CU) we developed a new colour vision test that works well with every kind of colour deficient observer and a simplified version of this test is now available on the web (For a detailed description of the CU Dynamic Colour Vision Test see: Barbur et al, Proc. Roy. Soc.B., 258, pp 327-334, 1994).

The movie below displays a moving "coloured" square that is buried in flickering luminance contrast noise. The square changes colour as the movie plays. You may be able to see the colour for some or all of the time. If you have some form of severe colour deficiency, you will have difficulty in seeing the "coloured" square moving all the time.

The movie lasts for 90 seconds and all you need do is play it and remember if the "coloured" square disappeared at any time during the movie. The absence of the moving square may only last for 2 to 3 seconds, before you see it reappearing in a different colour. This temporary disappearance of the pattern is what you have to watch for in the test. When this happens, you may like to confirm this with your optometrist who will be able to diagnose the type and severity of your colour deficiency loss.

The test itself

Depending on your browser, you may be able to click on the image below to run the movie. The movie is just over 12 Mb long, so it may take a considerable time to download over a slow link.

The web version of this test will run on a variety of monitors balanced for different phases of daylight. The movie was however prepared and will run best on a monitor balanced for ~9000K. This is usually the default factory setting for most colour monitors. The spectral characteristics of the pattern will be affected by ambient illumination and therefore this should be kept to a minimum (i.e., use the monitor in a dark room).

Acknowledgements

The new version of the colour vision test was produced with support from the UK Civil Aviation Authority. The test is not yet in use for medical certification purposes. It should therefore be used only as a guide.

The test is being made available on the web free of charge for your own use or for any colour screening programme you wish to carry out. The test is released under the terms of the GNU General Public Licence version 2. Source code (~3,000 PCX files) is available on request.

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City, University of London is an independent member institution of the University of London. Established by Royal Charter in 1836, the University of London consists of 18 independent member institutions with outstanding global reputations and several prestigious central academic bodies and activities.