A coloured overlay is a coloured transparent plastic sheet that can be placed on top of reading or copy text. It’s purpose is to minimise the discomfort of glare from a white page and to help mask the visual perceptual effects that can contribute to making reading unpleasant, or even impossible, for some individuals.
For some individuals a coloured overlay can improve clarity, support more accurate eye movements, and likely improve concentration and comfort. It is not known for certain how the coloured overlays work but some interesting theories have evolved from neuro-physiological research.
It should be remembered that the coloured overlay is simply a temporary tool to aid the progress of reading. The symptoms masked by the overlay are sometimes the result of an underlying deficiency in functional control over the visual system. More permanent improvements are possible with lenses and vision therapy activities and the overlay may then no longer be required.