Causes of Reading Difficulty

Contrast Sensitivity

If a child complains that text blurs or moves on the page, a sensitivity in the eyes is the culprit. Thankfully, there is a simple fix.

What is contrast sensitivity?

When a child complains of “words moving around” on the page, or that reading hurts the eyes, then you should suspect a sensitivity to the stark contrast of black text on a white background. If there is sensitivity there, then it can feel like this does for the rest of us.


The neurology behind this is that the eye begins processing the visual word while it is still in the eye. This means your eyes are basically a part of your brain sticking out of your skull! A bit freaky to think about… One of the eye’s most important processing jobs is finding shapes, which is performed by the millions of rods and cones in your retinae. If those rods and cones (which can vary from person to person) are extra sensitive to intensity, then you get this effect of shimmery or moving parts.

Some people call this “visual stress” or “Irlen Syndrome”

Fixing contrast sensitivity

An easy test for contrast sensitivity is to print on colored paper, or place a tinted overly on a page of text. Both things reduce the harshness of the contrast. If there is a clear improvement, then find an optometrist who can screen for this. The screener will find the right tint for making custom overlays or tinted glasses.

We should say that contrast sensitivity is quite a bit rarer than eye-tracking difficulties. The literacy world sometimes tends to believe the opposite, but experience shows that is not the case.

Interested in learning more? We literally wrote the book on it! Our Amazon bestseller on The 9 Main Causes of Reading Difficulty pulls back the neurological curtain on why YOUR child is struggling, and how to fix it.

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