As many as one in five children have problems with their vision that make it harder for them to read, according to research.

But scientists at Essex University have found that simply changing the colour of the page or wearing tinted glasses can make it easier for many pupils to read printed words.

On Friday, they began training teachers in the use of overlays - coloured plastic sheets to place over pages - which they hope will eventually be used by schools across the country.

The researchers believe that lines of text confuse nerve cells in the brain, causing them to fire inappropriately.

This means words can appear to "jump" on the page, and can seem distorted.

While as many as one in five children are affected, a study of 400 pupils found that up to 5% have severe difficulties.

Significant impact

But the research, funded by the departments of health and education, suggests that colour has a calming effect, which can help pupils read more easily.

Up to 20% of pupils at one school, Lakenham Middle School in Norwich, are already using the overlays, and teachers say their results have improved.

The university is now preparing to hold training seminars for interested teachers, to show them how to assess children and select a colour which works for each individual child - a process which only takes about six minutes.

The approach does not cure more serious problems like dyslexia, but scientists believe it could have a significant impact on the education of large numbers of pupils.

Liz Lewis, a teacher advising the research project, said: "What we'd like most of all is for teachers to become aware of this so they could at least do a preliminary screening and pick out children they think could benefit.

"The overlays are a very cost-effective method so once the children are detected, an awful lot of people could be helped."

Increasing recognition

The general phenomenon was first noticed two decades ago and initially was met with scepticism among scientists, since there was no apparent reason for it.

This has changed with time and with an increasing body of research evidence.

The Essex study is the first large-scale report on the incidence of the syndrome among schoolchildren in the UK and shows that the condition is more widespread than previously thought.

An American company which seeks to profit from assessing and treating children has opened centres in the UK. But most children who are affected still go undetected.