Harefield

Harefield
Harefield

Sunday, 29 July 2012

Magic Glasses

      When I was a teenager I was intrigued by advertisements in the popular press for magic glasses, also known as ‘X-ray specs’, that apparently allowed one to see straight through the outer clothing and glimpse buxom ladies in their underwear. I resisted the temptation to buy a pair but later on at university I did wear tinted spectacles in an effort to look cool in spite of being severely shortsighted. I quite literally saw the world through rose-coloured glasses – but then it was the late sixties … What I did not realise at that time was that they might also have cured my dyslexia, had I been unfortunate enough to have been dyslexic. It would be just too good to be true, would it not, if we could cure dyslexia with magic glasses?
            The answer, sadly, is yes. But that does not stop thousands of parents whose children are struggling to learn to read paying large sums for tinted lenses of doubtful utility. Nor does the lack of convincing evidence for effectiveness seem to restrain the enthusiastic advocacy for coloured glasses by those who service this market. Let’s look at the facts.
            First, it does not make conceptual sense to attempt to address a disability by supposedly alleviating problems in a modality unrelated to the known cause of the difficulty. You would not recommend a hearing aid for someone with a poor sense of smell. But as we know, and as the vast majority of reading scientists now believe, dyslexia, and reading disability more generally, almost always results from difficulties in processing language; specifically it appears to be a phonological processing deficit. Children who struggle to learn to read do so not because they cannot see the letters or words clearly but rather because they find difficulty in breaking words up into their component sounds. So why would coloured glasses make any difference?
            Second, even if we were to accept that there might be a small number of apparently dyslexic children whose problems are visual in nature, is the proposed remedy a credible solution? The problem here is that the hypothesised disabling condition, known as the scotopic sensitivity syndrome or the Irlen syndrome, is so unreliable diagnostically that many experts in vision doubt its very existence. In other words, coloured lenses appear to be the cure for which there is no known disease.
            Third, and hence unsurprisingly, the evidence for the efficacy of coloured lenses in helping to redress reading disability is tenuous at best with some studies finding no effect and some others claiming significant effects. Unfortunately, the studies claiming to provide positive evidence for efficacy are seriously flawed methodologically and are not accepted by most reading scientists.
         Finally, you don’t have to take my word for this but perhaps you might take seriously a joint policy statement on ‘Learning Disabilities, Dyslexia and Vision’ (revised 2009) from the American Academy of Pediatrics (Section on Ophthalmology, Council on Children with Disabilities), the American Academy of Ophthalmology, the American Association for Pediatric Ophthalmology and Strabismus and the American Association of Certified Orthoptists. Their conclusion is unequivocal:
“Currently, there is no adequate scientific evidence to support the view that subtle eye or visual problems cause learning disabilities.Furthermore, the evidence does not support the concept that vision therapy or tinted lenses or filters are effective, directly or indirectly, in the treatment of learning disabilities.
That this form of therapy simply does not work is plain to see, with or without tinted glasses.


August 28 2012 Note: A more recent review of LD, Dyslexia, and Vision is provided by the American Academy of Pediatrics: http://www.filedropper.com/visionanddylexiaamacadpaed

3 comments:

  1. Problem is, the modality in question *might* be related to the cause of the difficulty. What people know about the cause is another matter.

    Scientists have known for a long time that blue light suppresses the production of melatonin (a hormone that, among other things, makes us sleepy). Russell Foster's team found cells in the retina that play no part in vision, but contain a pigment called melanopsin that's involved in the regulation of circadian rhythms

    http://is.gd/UDNOPk

    Melanopsin also affects the production of glutamate, a neurotransmitter that plays an important role in the nervous system, including neurons in the brain. Other scientists have found that another neurotransmitter, dopamine, is released by rods and cones in response to light hitting the retina. Dopamine is an important factor in motor control. So it's completely possible that the amount of blue light entering the eye (that can be varied using coloured lenses) is affecting the functioning of the eye muscles, or the function of a number of brain areas involved in reading - or both.

    The fact that many children who have difficulty learning to read because they have a phonological processing deficit doesn't preclude them having a visual processing deficit as well, nor does it rule out a neurotransmitter deficit that affects both auditory and visual processing, modulated by the wavelength of light entering the eye.

    The major problem with research in this area is an implicit assumption that all children with <> or <> form homogeneous groups, which is highly unlikely given the complexity of the mechanisms involved in reading. So when an intervention doesn't improve the performance at group level (even if it does improve the performance of individuals) it's discounted prematurely.

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  2. What you say may indeed be possible and, if so, it would be important to provide empirical evidence as to how this affects reading. It is surely incumbent upon those who sell magic glasses to provide evidence for their efficacy. So far, they have failed to convince all of the relevant major professional associations in the US, whom one might have thought would know something about vision.

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  3. The majority of advocates of tinted lenses are practitioners. They would claim that they do provide empirical evidence for improvements in reading - based on self-reports by their patients. I think you are, rightly, asking for more rigorous evidence that most practitioners are not in a position to provide due to the cost of trials.

    I did point out that many research designs relating to reading difficulties are flawed because of an implicit assumption that people with reading difficulties form a homogeneous group, ie everyone in that group has the same cause for their reading difficulty. If a trial of the effect of tinted lenses on the reading ability of 100 people resulted in 3 showing a significant improvement, the conclusion would be that tinted lenses didn't improve reading ability - not that they might improve the reading ability of 3% of the population with reading difficulties. It would be unlikely that anyone would get research funding to investigate the 3 participants in question in more detail.

    As for professional associations; with all due respect to them, history suggests that professional associations are not homogeneous groups either - there's a diversity of opinion within them - and that sometimes the official view has been wrong. Until well-designed research is carried out on the effect of coloured light on reading ability, we can't say for sure whether it's effective for some people or not.

    I suppose what I'm saying is that since there is a plausible mechanism for tinted lenses being effective, the lack of supporting evidence isn't a good enough reason to dismiss the idea.

    logicalincrementalism

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