Scientists may have found a cause of dyslexia

Scientists may have found a cause of dyslexia
An example of OpenDyslexic typeface, used to try to help with common reading errors in dyslexia. Credit: OpenDyslexic

A duo of French scientists said Wednesday they may have found a physiological, and seemingly treatable, cause for dyslexia hidden in tiny light-receptor cells in the human eye.

In people with the reading disability, the cells were arranged in matching patterns in both eyes, which may be to blame for confusing the by producing "mirror" images, the co-authors wrote in the journal Proceedings of the Royal Society B.

In non-dyslexic people, the cells are arranged asymmetrically, allowing signals from the one eye to be overridden by the other to create a single image in the brain.

"Our observations lead us to believe that we indeed found a potential cause of ," study co-author Guy Ropars of the University of Rennes, told AFP.

It offers a "relatively simple" method of diagnosis, he added, by simply looking into a subject's eyes.

Furthermore, "the discovery of a delay (of about 10 thousandths of a second) between the primary image and the mirror image in the opposing hemispheres of the brain, allowed us to develop a method to erase the that is so confusing for dyslexic people"—using an LED lamp.

Like being left- or right-handed, human beings also have a dominant eye.

As most of us have two eyes, which record slightly different versions of the same image, the brain has to select one of the two, creating a "non-symmetry."

Many more people are right-eyed than left, and the dominant eye has more neural connections to the brain than the weaker one.

Image signals are captured with rods and cones in the eye—the cones being responsible for colour.

"b" or "d"

The majority of cones, which come in red, green and blue variants, are found in a small spot at the centre of the cornea of the eye known as the fovea. But there is a small hole (about 0.1-0.15 millimetres in diameter) with no blue cones.

In the new study, Ropars and colleague Albert le Floch spotted a major difference between the arrangement of cones between the eyes of dyslexic and non-dyslexic people enrolled in an experiment.

In non-dyslexic people, the blue cone-free spot in one eye—the dominant one, was round and in the other eye unevenly shaped.

In dyslexic people, both eyes have the same, round spot, which translates into neither eye being dominant, they found.

"The lack of asymmetry might be the biological and anatomical basis of reading and spelling disabilities," said the study authors.

Dyslexic people make so-called "mirror errors" in reading, for example confusing the letters "b" and "d".

"For dyslexic students their two eyes are equivalent and their brain has to successively rely on the two slightly different versions of a given visual scene," the duo added.

The team used an LED lamp, flashing so fast that it is invisible to the naked eye, to "cancel" one of the images in the brains of dyslexic trial participants while reading.

In initial experiments, dyslexic study participants called it the "magic lamp," said Ropars, but further tests are required to confirm the technique really works.

About 700 million people in the world are known to suffer from dyslexia—about one in ten of the global population.


Explore further

Dyslexia and sight: the wider view

More information: Left-right asymmetry of the Maxwell spot centroids in adults without and with dyslexia, Proceedings of the Royal Society B, rspb.royalsocietypublishing.or … .1098/rspb.2017.1380

© 2017 AFP

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User comments

Oct 18, 2017
But, switching eyes does not produce mirror images of letters. How could it?

It may produce double images, as both eyes are not necessarily focused on the same spot and confusion between which eye you should be following leads to jumbling up the letters.

JRi
Oct 18, 2017
How about just closing the left eye when reading?

Oct 18, 2017
If confusing competition between the two eyes was the cause of dyslexia, then reading with one eye closed would eliminate the problem. Surely this has been tried over the centuries, apparently without success.

Oct 18, 2017
Dyslexia also affects writing ability due to very poor spelling and this is unrelated to actually seeing the text, for instance ability to spell the words out loud is just as bad.

Thus they have not found the cause of dyslexia, just the cause of one of the strains of dyslexia. For instance in my dyslexia I confound j and g but not b and d or p and q...

Oct 18, 2017
Pay-walled...
So, must wait for 'secondary sources' to report on their 'magic lamp'.

Oct 19, 2017
I am mildly dyslexic.
If their theory is correct, I should find the words visually less confusing if I read with one eye shut.
So I tried doing that and found it makes no difference whatsoever to the visual confusion I see.
Thus their theory appears to be proven false from this trivial test.
I bet they didn't bother to make their test subjects do that trivial test and, if they had done so, they would find their theory is false. I bet this is just bad science.

Oct 19, 2017
Perhaps the reason closing one eye doesn't work lies in the brain not having sufficient "training/ experience" in correctly identifying the differences between letters. Using both eyes simultaneously with micro second lags allows for better discretion by the brain. If you see an iimage but your brain has always interpreted that image as the " same as", then you have no point of reference.
In science and nature, complex issues are rarely the result of a single problem.

Oct 23, 2017
The majority of cones, which come in red, green and blue variants, are found in a small spot at the centre of the cornea of the eye known as the fovea. But there is a small hole (about 0.1-0.15 millimetres in diameter) with no blue cones.
This has a wrong word. It is retina, not "cornea".

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