When ever we are looking at white paper, all of the visible light spectrum (the rainbow) is reflected into our eyes. For people with Irlen Syndrome, some of these wavelengths of light cause visual distortions and discomfort. This makes it difficult for some children to learn to read. The coloured overlays actually filter out some wavelengths of light and so remove the visual distortions and discomfort. This makes it much easier for the children to learn to read, because they can focus on what they are trying to learn.