A person's eye colour can be predicted with 90 per cent accuracy by testing just six genes, according to research that opens new possibilities for health screening, forensic science and the creation of “designer babies”.

The findings show that scientists can forecast how multiple genes combine to affect human health and development, and could greatly expand the scope and value of DNA tests.

The research, however, could also open fresh ethical controversy over genetic testing of embryos, as it suggests it would be possible to screen for eye colour so that parents could increase their chances of having children with a particular look.

At least one American fertility clinic has already offered screening for cosmetic traits such as eye colour, though it recently withdrew the service after negative media coverage.

While it is already possible to diagnose health risks that are caused by single genes with strong effects, most human traits are governed by many genetic variations, each of which by itself has only a small impact.

These are known as “complex traits”, and include common diseases such as diabetes and heart disease, as well as characteristics such as eye colour, height and intelligence.

The new research, by a Dutch team, offers a strong indication that it is possible to predict complex traits with reasonable accuracy from the results of a DNA test.

This would be extremely valuable for personalised medicine, as multiple genes could be examined to estimate an individual's risk of developing a wide range of health conditions. Scores of genetic variations that raise the risk of disorders, but do not invariably cause them, have been identified by scientists in the past two years.

Companies such as 23andMe, Navigenics and deCODEme have already launched personal DNA services that screen for these variants, which are sold directly to consumers over the internet, though their value in predicting disease has not yet been clinically validated.

In the study, which is published in the journal Current Biology, a team from the Erasmus Medical Centre in Rotterdam used eye colour as a model to examine whether complex traits could be predicted from DNA test results.

They identified 37 variations in eight genes that are known to affect eye colour, and tried to predict real people's eye colour from their test results.

If subjects had blue or brown eyes, the scientists were able to get the right result 90 per cent of the time by examining just six of the variations. For the 10 per cent of people with intermediate eye colours, such as green, accuracy was lower, at about 75 per cent.

As well as indicating that complex traits can be predicted by testing several genes, the findings could also have implications for forensic science. It may be possible to use DNA left at a crime scene to predict the eye colour, hair colour or even the facial appearance of a suspect - though careful interpretation would be needed as there would be a high error rate.

The scientists warned that their findings applied only to people of Dutch European descent, and that they are unlikely to be relevant for people of different ethnic groups.

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