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Visual Stress, SLD & Colorimetry

What is visual stress?

Visual stress (Meares-Irlen Syndrome), explained simply, is a sensitivity to visual patterns and, in particular, stripes. In some individuals this condition can cause perceptual problems that interfere with their reading. These symptoms can occur even if normal vision is present.

A current scientific explanation for this is that the perceptual problems are due to a hyperactivation of the visual cortex within the brain, particularly in the more anterior or frontal visual areas. As it happens, this can be reduced by a precise and unique colour.

What are the symptoms of visual stress?

Symptoms of visual stress may include any or all of the following:

  • Movement of the printed text
  • Blurring of the printed text
  • Letters changing size or shape
  • Patterns visible in the print (described as ‘rivers’ or ‘worms’)
  • Halos of colour surrounding letters or words
  • Tiring easily whilst reading
  • Visual discomfort and/or headaches
  • Red, sore and/or watery eyes


Visual stress and dyslexia

Visual stress is NOT the same as dyslexia but visual stress is more common in those who are dyslexic. Dyslexia is the term that is used to refer to reading problems that are not the outcome of poor teaching and is often associated with difficulty spelling. People are often misdiagnosed as being dyslexic due to a poor reading ability and that is why it is important that visual stress is identified as early as possible.

What is dyslexia? 

Dyslexia, also known as Specific Reading Difficulties (SRD), is a condition where an individual has a difficulty learning to and being able to read that is not consistent with their intellectual ability. It cannot be diagnosed or cured by completing a visual assessment and undergoing treatment, nor can a poor reader be turned into an average reader. Instead, the aim of a visual assessment is to make the visualisation of the text as clear and as comfortable as possible for the individual.

How do we assess visual stress?

Firstly, the patient’s symptoms need to be established with the use of a pre-assessment questionnaire and by doing this the patient has the opportunity to recognise and identify any difficulties they may be having. Some of these difficulties may have been present all of their life but when presented with the appropriate question it may be found that this is in fact something that can be treated. Often symptoms such as blurring, moving and doubling of text along with headaches are reported and it may be that these symptoms had not been reported previously.

What does the assessment involve?

During the assessment there are 3 areas of visual function that are examined. These are:

1. Focusing ability

This looks at long-sightedness (i.e. the increased effort needed for near vision), short-sightedness (i.e. poor distance vision), astigmatism (i.e. where both distance vision and near vision are affected) and accommodation (i.e. the ability to change focus from distance to near and vice versa)

2. Binocular vision

This refers to the ability of the two eyes to work together. It is possible for the eyes to work perfectly well individually but if they do not work well together then the patient will have difficulties. Symptoms that are often present when the eyes are not working well together include double vision and/or moving of text.

3. Response to colour

When viewed against a coloured background, some people find text clearer and therefore easier to read than if the same text were presented as black on white. When carrying out an assessment, each patient is unique and therefore a randomised test is used to select the most appropriate coloured overlay for them. However, this test is subjective and therefore may not be suitable for young children.

What can be done to manage visual stress?

The management of visual stress can include any and/or all of the following:

  • Spectacles

These can be issued to correct long-sightedness, short-sightedness, astigmatism and some binocular vision issues.

  • Eye exercises

These can be used to help improve accommodation issues and some binocular vision issues. These are often carried out at home and progress is monitored by way of regular follow-up appointments with the optometrist.

  • Coloured overlays

These can be issued if the assessment indicates that they would be beneficial. The coloured overlays are used for a period of 2 – 3 months whereby the patient uses them on a voluntary basis. After the overlays have been used for this period of time and they have proven to be significantly beneficial to the patient then tinted spectacle lenses may be advised. The colour of the tinted spectacle lenses will be more specific to the individual’s needs and is very often a different colour to that of the overlays that had previously been issued. Tinted spectacles lenses are often more convenient than overlays for use at a computer or for looking at a board.

If you would like to book an assessment or have any queries relating to this service then please contact our practice in Churchdown directly. Alternatively, for further information at this point please refer to the following documents:




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