Thousands of people prevented from becoming pilots because of their colour-blindness could get another chance to follow their childhood dreams, thanks to the development of a revolutionary eye test.
Until now, people with even minor forms of the condition – which affects one in 20 men and one in 200 women – have been unable to fly commercial aircraft because traditional tests are only able to detect that the problem exists, not its severity. But a new examination developed by scientists at City University in London can pinpoint the exact level of a person's colour-blindness and immediately indicate whether their vision meets the minimum requirements for flight safety.
Colour-blindness is caused when the eye's light-sensitive cells, known as "cones", are faulty or missing. The most common form is red-green deficiency, in which the subject may be unable to distinguish between the two colours. Most people are born with it, but it can also arise as a result of illness or medical treatment.
The new test stems from research sponsored by Britain's Civil Aviation Authority (CAA) and the US Federal Aviation Administration, which wanted to establish a more accurate way of assessing a person's colour vision to create fairer guidelines for those hoping to become pilots. In a report, the CAA estimated that using the new method will allow more than a third of those affected by colour-blindness to become pilots.
Try the test for yourself
It said: "If the new standard and tests were to be adopted, it is anticipated that, on average, 35 per cent of applicants currently excluded on the basis of conventional colour vision tests would be accepted as safe to fly."
Colour-blindness affects far more men than women because it is almost always passed down on the X chromosome. It has only to appear on a man's single X chromosome for him to be affected; for a woman it must be present on both X chromosomes.
For commercial pilots, good colour recognition is crucial when guiding a plane in to land, because runways are equipped with special lights that change colour depending on the angle of the plane's descent. Eye tests are a requirement for those who want to pursue jobs in the military, police, fire service and transport sectors as well as aviation. Many employers in these areas are likely to follow the CAA's lead in putting the new test to use.
Sally Evans, the CAA chief medical officer, said the authority hoped to start putting applicants through the new test within two or three months. Yesterday, she addressed a meeting in Latvia of the chief medical officers of Europe's main aviation authorities to promote its use. Those who have previously been rejected because of their colour-blindness are being encouraged to try again.
"Because some people in the past were put off from even applying if they knew they had a colour deficiency, it is difficult to say what proportion of potential applicants are being excluded at the moment," Ms Evans said. "But anybody who has failed in the past is welcome to apply, although obviously there isn't a guarantee that they will pass this time."
Seeing is believing: The new test
* In a standard Ishihara test, a person is shown green, red and orange dots in patterns. Colour-blind people cannot differentiate between the colours and pick out a pattern.
* In the new test, the person is shown coloured blocks in a grey square that jump to new positions as he tracks them. The process is repeated with different colours and hues. A colour-blind person will eventually be unable to detect the blocks' movements. The test shows how weak the colour was when it disappeared, placing the person on a colour-blindness scale.
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