Visual Stress



What is visual stress?

Visual stress is a term used to describe visual discomfort and perceptual distortions in the printed text, suffered by many people who struggle to read. The condition is estimated to be present in about 40 % of poor readers and in 20 % of the general population in varying degrees.

Coloured overlays can improve reading speed and accuracy. They can enable longer periods of reading free of discomfort.

colour overlays

The symptoms can occur despite normal vision and can include:

  • movement of print
  • fading of print
  • letters changing shape or size
  • letters fading or becoming darker
  • patterns appearing, sometimes describes as “worms” or “rivers” running through print
  • illusions of colour – blobs of colour on the page or colours surrounding letters or words
  • rapid tiring
  • headache or eyestrain


  • moving closer to or away from the page
  • becoming restless when reading
  • using finger as a marker
  • skipping words and lines
  • rubbing eyes and blinking excessively
  • low self esteem

Dyslexic individuals are more likely to experience visual stress than others, although visual stress is quite distinct from dyslexia.

Many thousands of individuals who find reading tiring and unpleasant, unknowingly experience visual stress.A number of these could be helped by overlays or Readez Tinted Lenses. It is therefore essential that every child who struggles to read is referred to an optometrist who can undertake a full eye examination and check for the presence of visual stress.

A diagnostic process has been designed that allows for the identification of this type of visual stress, thereby distinguishing it from other barriers to reading. This is achieved by the simple selection of an optimum coloured overlay placed over the reading matter.

Is your child falling behind with reading?

In some cases, reading difficulties can be caused by vision problems such as long-sightedness, astigmatism or problems coordinating the eyes.  This can be ruled out by having your child’s eyes examined by one of our Optometrists.

If having ruled out dyslexia and checked that your child’s eyes are healthy, your child is still having problems reading, they might be one of the 20% of the population who suffers from a condition known as Visual Stress.

The good news is that the symptoms can often be reduced by using a coloured overlaycoloured lenses or by changing the background colour of the screen or tablet that they are looking at.

The ReadEZ system was developed at City University London by a team led by optometrist and visual scientist, Professor David Thomson. The system is used by over 400 Opticians and in many hospitals and schools and our coloured overlays, coloured lenses and screen tinting software are now used by 1000s of people around the world.

How do I book a Visual Stress Assessment