He noticed that a lot of the people seemed to have a family history of migraine or repetitive headaches. He began to wonder whether some of the headaches could be caused by reading, and if so, if migraine patients could be treated with the same coloured lenses he was using to treat his dyslexic patients.
His very early studies seem to show that tinted lenses can prevent migraine.
It was two years ago that Dr Wilkins, a psychologist at the Medical Research Council's Applied Psychology Unit in Cambridge, began to investigate. Among the patients referred to him for recurrent headaches, he found 'that they had sensitivity to glare; it is almost like a sign that their headaches could be caused by reading,' he says.
In one study that Dr Wilkins read, , 35 of the 40 patients claimed that they or family members suffered from migraine or frequent headaches, although only four had been diagnosed with migraine. Migraine is ordinarily found in only one out of 10 people. Looking further into the connection in scientific literature, Dr Wilkins repeatedly found anecdotal references to headache and tinted spectacles.
His own studies into, and interest in, the possible causes of discomfort associated with reading had also frequently raised headaches, eye strain or distortion of the text as possible reasons.
The case of one 45-year-old patient with a 10-year history of migraine attacks several times a week illustrates the remarkable results the coloured glasses could have. In her case the effective lenses were yellow. 'The lady had been in hospital with a suspected cranial haemorrhage, but a scan showed nothing. We tried her out on tinted lenses and now she considers herself cured. She has only had one attack in six months,' Dr Wilkins says.
He also recounts the story of a 14-year-old girl who suffered daily headaches behind her right eye and complained that the letters of words on the page appeared unstable. When the girl was given yellow lenses, her headaches became less frequent and she wrote in her diary that the glasses had 'removed all the stress from my eyes that I did not know was there. I can read much faster'.
As with dyslexia, the colour of the lens that helps migraine sufferers varies by individual. While both these patients did well with yellow, Dr Wilkins and his PhD student, Ed Chronicle, reported in The Lancet in 1991 that migraineurs tend to avoid the colour red and opt for blues or greens.
To determine the best tint for people with reading difficulties, Dr Wilkins has designed the Intuitive Colorimeter. The instrument allows a person to look at text through a lens while the colour, its depth and amount of illumination is changed until the patient decides which is the most agreeable.
Dr Wilkins and fellow researcher Dr Bruce Evans, an optometrist at the Institute of Optometry, theorise that pattern 'glare' may be one cause of migraines. Pattern glare describes the discomfort people feel when they look at certain patterns, particularly close horizontal or vertical stripes. Sufferers see anomalous effects, such as bending or waving of the stripes, or images jumping about or a lattice-like structure. Others see colour shadows behind the printed shapes or perceive the lines to be fading or flickering.
'The number of illusions people see seems to be directly proportional to the discomfort they experience,' Dr Evans says.
In people with epilepsy, these patterns can induce fits. Migraineurs, too, appear to be more sensitive to pattern. Dr Evans explains: 'One study found that pattern sensitivity occurred in 82 per cent of migraineurs. It occurred in 18 of 22 subjects who experienced recurrent but non-migraine headaches on reading. But more telling is that there were no cases of pattern sensitivity in 42 subjects who did not experience headaches when reading.'
Further research by Dr Wilkins has shown that people suffer more headaches after they have looked at striped patterns.
Pattern glare can be caused by more than simply stripes and waves, says Dr Wilkins. Some printed pages can resemble a pattern of horizontal lines, which Dr Wilkins proved in earlier studies when the text from books brought in by patients was compared. The books were divided into two groups, one the patients said were difficult to read, the other easy. At first glance the text appeared similar. But when put through a computer filter that reduced the distinction in the text, stunning differences came to light.
The computer images revealed that text from the 'difficult' books merged into continuous lines of black stripes on a white page. But text from the books that gave no problem became unconnected blobs of black on a line.
According to Dr Wilkins, the text that most resembles stripes and which causes difficulty is print with little space between the lines and with words jammed together. Print that contrasts strongly with the background, as with bold type faces, also causes problems.
But why should patterns and text cause discomfort and induce headaches in some people? It has been suggested that these people are hypersensitive to visible stimulation. In some way their brain becomes overloaded by the information their eyes are sending it, explains Dr Wilkins. Certainly in people with photosensitive epilepsy, patterns that can induce fits produce bursts of brain activity.
'And we know that the excitation can be fairly focal because some patients are sensitive to only one pattern or orientation,' Dr Wilkins says.
Dr Evans takes this theory further. He suggests that pattern sensitivity could be one condition expressing itself in different severities: 'You could have a condition of hypersensitivity so that if you are particularly sensitive you get epilepsy, if it's not as sensitive you get migraine.'
The coloured lenses would seem to work by dulling or cutting down on the information the brain receives, says Dr Wilkins. But he is still unsure why the colours have to be specific to the individual.
Despite early successes, both Dr Wilkins and Dr Evans are reluctant to say definitely that coloured lenses can help reduce migraine. The theory, they agree, needs to be tested in double-blind trials where patients are given two pairs of spectacles with similar but different coloured lenses selected under the Colorimeter. They would then be asked to keep a diary of symptoms for each pair of glasses.
The two researchers are applying for grants to fund this project.