Precision ophthalmic tints (POTs) have been gaining increasing popularity in preventing migraine attacks. Over the last 10 years about 25 thousand tinted glasses have been prescribed (1). The hypothesis explaining how the specs work was based on presumably soothing effect of the lenses on visual cortex hypersensitivity. The recent study (2), published in the journal Cephalgia, was designed to investigate the neurological basis of a beneficial effect of POTs. Functional magnetic resonance imaging (fMRI) was successfully used. Scientists from Michigan and Essex Universities managed to explain how the use of simple glasses can change a brain activity and what it has to do with migraine.
According to some studies (3) about 10% of the worldwide population is affected by migraine. 40% migraineurs report visually provoked attacks. In patients suffering from migraine with aura (MwA), the aura is visual in 90% of the cases. Sufferers are susceptible to strong visual stimuli and find them aversive. This fact inspired the scientists to search for the visual aspects of headaches. It turns out that certain patterns, such as high contrast stripes, “gratings” or bright light can trigger migraine attacks. Strong visual input causes a rapid spread of excitation through hyperexcitable visual cortex. Neurons function inappropriately which promotes perceptual illusions, distortions, photophopia and vision blurring . This can lead to a migraine attack or, in cases of photosensitive epilepsy, an epileptic seizure.
The idea of cortical hyperexcitability is supported by many facts. To start with, migraine and epilepsy are co-morbid conditions. Moreover it has been provediv that anticonvulsant drugs, such as lamotrygine or topiramat, can prevent migraine headaches. In response to visual stimuli, the potential evoked in visual cortex has a high amplitude and does not show habituation with repeated stimulationv, but it can be reduced by sodium valproate. Hyperactivity of visual cortex probably results from the imbalance of inhibitory neurotransmitters and excitatory aminoacids.
For some patients the image of text resembles a pattern of stripes and causes difficulties in reading. This was one of the first applications of tinted lenses as they reduced distortions seen in texts and increased the speed of reading (6). Visual discomfort is sometimes referred to as visual stress which describes a group of symptoms and signs connected with the perception of print. The color of appropriate specs needs to be selected individually. A special device called Intuitive Colorimetervii is used under the direction of Optometrist. It was designed by Professor Arnold Wilkins in order to assure full precision of the selection of one of 100,000 available color combinations. Apart from dyslexia and migraine, POTs can be helpful in photosensitive epilepsy, head injury, autism and multiple sclerosis.
It has been hypothesized that migraine-comfortable colors silence the cortical excitation which results from massive visual stimulation. Only now has it been proved that tinted glasses really have an effect on brain function. The study discussed in this article investigated 11 patients who suffered from migraine. Participants were firstly prescribed their personal POTs using the Intuitive Colorimeter. Every patient was paired with a control, who was healthy. These subjects were tested with the patient’s set of lenses. There were three types of lenses used in the study: POT, grey lenses and glasses of random color.
During the fMRI scanning patients were exposed to a selection of striped patterns causing a different degree of visual stress. The subjects reported some relief using all the lenses, but the POTs led to a 70% discomfort reduction. While being shown non-stressful patterns, the patients did not report any beneficial effects of the lenses. POTs exclusively inhibited cortical activation for migraine sufferers in visual area V2 of the occipital cortex. Moreover, the effect spread to extra-striate visual areas V3, V3A and V4.
Previous studies showed that 42% of MwA sufferers reported that their frequency of headaches decreased by 50% when using precision-tinted lenses. Now we know that these data do origin from the real effect of POTS on the human brain. Taking into consideration all of the treatment methods for migraine, including drugs burdened with dangerous side effects, color glasses seem to be a safe and friendly alternative. Sometimes the simple option seems to be the best option. Thanks to the recent study on POTs we gain more insight into the pathogenesis of migraine attacks and in future we may hope for an optimal and successful treatment for every migraine patient.
1.Drug Dev Res. 2007;68(7):469-475. Prevention of Visual Stress and Migraine With Precision Spectral Filters.Wilkins A, Huang J, Cao Y.
2.Cephalalgia. 2011 Jun;31(8):925-36. Epub 2011 May 26. efMRI evidence that precision ophthalmic tints reduce cortical hyperactivation in migraine. Huang J, Zong X, Wilkins A, Jenkins B, Bozoki A, Cao Y.
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6.Res Read. 2004;27:152–162. Visual stress theory and its applicaton to reading and reading tests. .Wilkins AJ, Huang J, Cao Y