Thousands of pupils underachieve at school because they suffer from “undiagnosed vision-linked stress syndrome”, Ian Jordan, a leading research optician, told the international Inclusive and Supportive Education Congress (ISEC) last week at Strathclyde University.

The condition is believed to be exacerbated by powerful fluorescent school lights which affect many children with visual perceptual problems who are highly sensitive to certain light frequencies. They have difficulties seeing words properly, concentrating and even hearing clearly.

A study at Crieff primary to measure the effects among 8-10s found that 27 per cent reported significant symptoms of vision-linked stress syndrome which had gone undetected in many of them. Out of 111 pupils, 30 reported more than 10 symptoms when they looked at print on the page.

Children described difficulties such as seeing double, words being jumbled up, words disappearing or being blurred, or looking funny as if squeezed together, and letters being upside down or moving about.

The researchers, who were testing the hypothesis that lighting conditions in the classroom could affect performance, were surprised at the numbers of children affected. Sandra Paterson, a learning support teacher who led the trial, told the conference: “When you hear what some of these children were experiencing, you wonder how any of them were managing to make any progress in reading at all” Mr Jordan, who was also involved in the study, said: “The usual diagnosis is that they don’t concentrate or that they are lazy. Virtually none was recognised as having a problem and the teachers were surprised by the children’s answers. People are assumed to be able to see the same; this is not true.”

Despite the fact that 70 per cent of information is taken in through the eye, visual perception problems (also known as vision dyslexia) are not detected by standard education, visual or medical tests. Once identified, symptoms can be alleviated by the use of tinted lenses.

Mr Jordan, who has developed a range of lenses to treat the condition, believes many teachers are unaware of problems pupils are having and mislabel them as low achievers. He warned there were potentially huge implications for schools and local authorities since other senses such as hearing, touch and memory were affected.

Pupils reporting problems were given tinted glasses which led to a significant reduction in symptoms from an average of 12.4 to 6.8. Teachers reported rapid improvements in organisation and in writing skills with some children able to write legibly for the first time.

“There is the potential for real improvement,” Ms Paterson said. “One child had gone up two years in reading age. But, when the spectacles were mislaid, the improvements were reversed.”

Val Corbett’s son, Sean, spent five years struggling with the condition before it was diagnosed. Sean, aged nine, exhausted himself trying to do well and teachers regarded him as a good, intelligent pupil but a bit of a day-dreamer. Since the condition was identified, Sean has started to enjoy reading for the first time and has much more confidence at school.

“The glasses slowed his visual processes down and he can hear more clearly now,” his mother said. Later this month he will start piano lessons and is learning to read music.