What are coloured overlays?
Coloured overlays are sheets of translucent or transparent coloured plastic that can be placed over a page of a book so as to colour the text beneath without interfering with its clarity. Coloured overlays reduce the perceptual distortions of text that children sometimes describe. They enable some children to read text more fluently and with less discomfort and fewer headaches. Each individual seems to need a different colour, so it is important to assess the effects of a wide range of colours.
What are the symptoms?
Visual perceptual distortion should be suspected in children who have trouble learning to read, particularly if they report headaches and eye-strain from prolonged exposure to the page. If the child reports any illusory movement of the letters or words, or glare from the white paper, then treatment with coloured overlays or filters should be considered.
One possible question to ask is: “After you have been reading for a while, do the words or letters do anything different?“. If open-ended questions such as the above fail to provoke reports of distortions, more direct questions can be given. The child can be shown a page of text, and asked the following questions: “Do the letters stay still or do they move?”; “Are the letters clear or are they blurred (fuzzy)?”; “Is the page too bright, not bright enough or just about right?” ; “Does it hurt your eyes to look at the page or is it OK?”. Reports of movement, blurring and glare are more likely in children who benefit from overlays.
What is included in the assessment?
The precise routine will vary from one optometrist to another but the basic eye test includes refraction (tests of lens focus), acuity (ability to see small objects), tests of the health of the eyes, and basic tests of ocular motor function (how well the eye muscles work together). There are other tests that are not always included in the examination but are generally thought to be particularly important for children with reading difficulties. You can ask the optometrist whether they would do these tests before you book an appointment.
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