It's all in the eyes.
That is the conclusion that French researchers draw in the magazine Proceedings of the Royal Society B. The researchers studied the eyes of 30 students with dyslexia and then compared them with the eyes of a control group consisting of 30 students without dyslexia. They soon came across a difference between the two groups. The difference was in the arrangement of light-sensitive 'blue' cones in the eye.
There are various light-sensitive cells on the retina: cones and rods. The bars come in three variants: cones that are sensitive to blue, green and red light. Most of the cones are located in the heart of the retina, in the fovea centralis (also called the central groove). But in the central groove there is a tiny circle in which there are no cones at all. For the sake of convenience, let's baptize the cone-free zone. What the researchers have now discovered is that the arrangement of cones around this cone-free zone is very different in the eyes of people with dyslexia than in the eyes of people without dyslexia. For people without dyslexia, the cones are arranged in one eye so that the cone-free zone is nicely rounded and in the other eye so that the cone-free zone is irregular in shape. But in people with dyslexia, the cone-free zone is round in both eyes.
Image: Skitterphoto / Pixabay.
What does that mean? You have to remember that everyone who looks at the world with two eyes continuously receives two slightly different versions of the same image. And the brain has to choose one. In addition, the brain is guided by the dominant eye: the image of that eye is slightly better than that of the other eye. What the research now shows is that people without dyslexia have a round cone-free zone in their dominant eye. People with dyslexia have two round cone-free zones and therefore no dominant eye, the researchers say. And that results in the brain being presented with two slightly different images and having to make something out of it. And that's probably where things go wrong, the scientists write: "The lack of asymmetry can be the biological and anatomical basis for reading and spelling problems in people who can see well but are dyslexic."
If this is indeed the cause of dyslexia, then we have found a fairly easy way to diagnose dyslexia. One only needs to look into the eye. In addition, the researchers think that this difference between people with and without dyslexia can be treated fairly well.