- Eye Health
Coloured Overlays to Reduce Visual Stress
What are coloured overlays?
There is now scientific research to show that both coloured filters (worn as spectacles) and coloured plastic sheets laid over text (known as overlays) can help some children to read. 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.?
What do they do?
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. It is important to assess the effects of a wide range of colours because individuals do not all benefit from the same colour.
What are visual perceptual distortions?
Some people can experience distortions when they look at certain materials, particularly text. The distortions of text include blurring movement of letters, words doubling, shadowy lines, shapes or colours on the page, and flickering. These distortions are characteristic of a condition that some have called Meares-lrlen Syndrome, Irlen Syndrome or Scotopic Sensitivity Syndrome. Individuals with migraine are particularly susceptible to the distortions.
The people who benefit may be good readers, but more often they have difficulty reading. They usually suffer visual discomfort when reading and, when questioned, will often report perceptual distortions of the text. These distortions usually include apparent movement or blurring of the letters and words. Often there is a family history of migraine.
Why can someone have 'perfect eye sight' and still experience distortion?
An optometrist will report 'perfect eye sight' when someone can see a letter chart without the need for spectacles, and when there are no problems of co-ordination between the eyes. The perceptual distortions may occur quite independently of any focusing? problems, although they are often, but not always, associated with a minor problems of moving the eyes together and keeping the direction of gaze appropriately co-ordinated.
Does visual perceptual distortion occur in families, and if so, why?
Many traits run in families and visual perceptual distortions are no exception. The genetic contribution is the subject of investigation.
Are coloured overlays needed permanently?
It seems that people benefit most from colour if it is offered as soon as any reading difficulty is suspected, before the cycle of failure has begun. Many 7 year-olds appear to use coloured overlays for a year or two and then discard them as unnecessary. This may be because the acquired familiarity with text makes the distortion less distracting.
What do I do to find out if colour might help?
The optometrist will perform an examination with a pack of coloured overlays. and decide which colour, if any, reduces the reported distortions. Another way of assessing benefit is for the examiner to administer the Wilkins Rate of Reading Test .
The rate of reading words on this test is usually more than 10% higher with the chosen overlay than without for someone who will benefit from using an overlay.
Will there be a charge for these an overlay assessment?
The NHS only pays optometrists a small fee for carrying out a basic eye examination. As the assessment is of a specialist nature, requiring a separate appointment we charge a private fee for the detailed investigation of people with reading difficulties.