Education authorities and schools in the West Midlands have come under increased pressure to screen pupils for "visual dyslexia".

Experts believe as many as 20 per cent of pupils may suffer from the condition ? also known as ?visual stress? ? to some degree.

But despite it being relatively easily corrected with the use of coloured lenses, few authorities have invested in the equipment to test children for it.

A national conference to highlight the condition is to be held at Birmingham?s Aston University in the autumn.

Organised by pressure group Colour for Vision, it will include presentations on the latest research showing how failure to spot sufferers can lead to under-achievement in future life.

Christine Fitzmaurice, spokeswoman for the group, said: ?This is something that potentially affects a significant number of pupils.

?A typical class of 30 may have two or three youngsters who?s vision can be considerably improved using coloured lenses.

?There is funding in schools for such things and it isn?t a big investment to help rectify a huge problem.

?Not picking up the condition can have a huge impact on a child?s education.?

Symptoms of visual stress range from words appearing to swim around on the page and letters fading or changing in size, to nausea, dizziness and headaches.

It differs from the most commonly understood form of dyslexia in that the condition can be corrected with the use of tinted lenses. Campaigners estimate about five per cent of pupils in a typical school will suffer from it.

Screening packs containing coloured overlays can be purchased relatively inexpensively, but a lack of awareness has restricted screening in most schools.

Ayrshire in Scotland and Norfolk are among a handful of authorities that have recognised the condition and introduced screening.

In Birmingham there are only about two or three opticians with the specialist equipment, called a Colorimeter, needed to detect and treat sufferers identified with the condition.

Nationally, there are 160. Ms Fitzmaurice added: ?What is needed is a new approach to looking at children?s vision.

?Every child should have a full visual check after the first year at school. And every school should carry a set of overlays to screen children.

?If any child shows any difficulty with learning to read by the age of six they should have overlay assessment.?

Speakers at the conference, to be held on October 21, include Dr Frank Eperjesi of Aston University?s Vision Science Department, one of the few centres specialising in the condition.

Dr Pamela Heaton of Goldsmiths College, London, will discuss results of her recently published research showing how the use of coloured lenses can help people suffering autism.

Another study conducted in a prison and to be highlighted at the conference found 34 out of 51 experienced reduced perception distortions and increased reading speed using coloured overlays.

Last year education chiefs in Birmingham expressed interest in providing training for teachers in how to spot visual dyslexia through Aston University.

Councillor Les Lawrence (Con Northfield), Birmingham City Council?s cabinet member for education, said at the time: ?Anything that leads to early intervention and improvement in education would be welcomed.? n To book a ticket for the conference contact Aston University on 0121 204 3900.