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Visual Stress And Dyslexia

Refers to reading difficulties, light sensitivity and headaches from exposure to disturbing visual patterns. It can be responsible for print distortion and rapid fatigue when reading. The severity of these symptoms can vary from person to person. The symptoms can occur despite normal vision. Approximately 5% of the population are severely affected by Visual Stress and 20% to a lesser degree.


Movement of print
Blurring 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 page
Becoming restless
Using finger as a marker
Skipping words and lines
Rubbing eyes and blinking excessively
Low self esteem

When we look at someone wearing a very stripy shirt it may feel uncomfortable for us to look at and it may “make our eyes go funny”. This effect can be seen by many individuals who look at print as this is often a “stripy pattern”.

Symptoms of visual stress are not always immediately obvious. Many individuals who suffer with this condition believe the discomfort they feel when reading or the distortions they experience on the page are “normal” and experienced by everyone. That is until someone presents them with an appropriate colour and they realise that reading can become more comfortable and even enjoyable.

The simple application of an overlay at an early stage could save years of anxiety and prevent the downward slide in confidence which occurs in most cases where children struggle to read.


Dyslexia is a term used to describe various specific learning difficulties that affect the ability to learn to read and spell correctly. Visual Stress is NOT Dyslexia but can be particularly prevalent in Dyslexic individuals. If Visual Stress is identified and colour is used to alleviative some of the symptoms then other learning difficulties such as Dyslexia are easier to cope with.

Many people with Dyslexia may also suffer with visual stress and can therefore be helped by colour. Equally there are a large percentage of children and indeed adults who are not identified as being Dyslexic but still suffer with these symptoms. The appropriate coloured overlay or Precision Tinted Lenses can also help this group of individuals.

It is therefore important that overlays should not be reserved only for those pupils who have been “statemented” or identified as being in need of specific help. They should be available to any child who does not naturally like to look at books.

Intuitive Colorometer (Colourimetry)

This instrument was developed by Professor Arnold Wilkins and the Medical Research Council and is fully supported by research studies and peer reviewed controlled trials.

It is used under the direction of an Optometrist to logically and sequentially explore colour space to find the optimal Precision Tint for the relief of perceptual distortions in Visual Stress.

The instrument independently changes the 3 parameters of colour, hue, saturation and brightness while the eyes are colour adapted. This will give a final colour which is extremely precise to each individuals needs. The colour will be different for each person and the precision coming from a choice of over 100,000 colour combinations now available. In its most effective form this prescription will be delivered as Cerium Precision Tinted Lenses.

The tint is selected rapidly and efficiently in an examination lasting about 20-30 minutes carried out by a specialised practitioner.

The optimal colour which will benefit each individual can change over time, especially with children. It is therefore very important that the patient visits the specialised Optometrist regularly for re-evaluations.


The use of an overlay has been shown by Professor Arnold Wilkins at the Medical Research Council at Cambridge to enable an increase in reading fluency, efficiency and duration. The same research also demonstrated that the colour selected will vary for each child.

The overlay assessment can be carried out, by Brosgill Opticians, at our Street Lane and Ilkley branches to screen pupils who exhibit symptoms of Visual Stress.

It is recommended that the overlay should be used without prompting to eliminate any possibility of placebo effect. If there is continued use of the overlay for a period of 6 weeks- a school term, and there has been beneficial reports from the teacher/parent then an assessment with the Intuitive Colorimeter at Brosgills Street Lane is recommended. Precision tinted lenses can then be prescribed which provide a much more accurate and precise colour for each child and will also be more convenient for board and computer work. Studies have shown that many individuals need a precise colour which can only be found with the Intuitive Colorimeter.

Research has shown that the colour chosen as an overlay may not be the same as that chosen by the Intuitive Colorimeter. It is therefore not acceptable to offer lenses tinted to match the colour of the selected overlay. Lenses tinted in this way may offer very little benefit.

FAQ for Visual Stress

Can you have perfect eyesight and still experience visual stress?
YES, perfect eyesight means you can read all of the letters on the chart without glasses and both of your eyes work together in the way they should. Visual stress can come from a binocular anomaly, but this will be corrected before any colour is used. If Visual Stress is still occurring after all binocular problems have been sorted the cause is likely not to be due to the eyes but the visual cortex part of the brain. Colour is likely to help on these cases.

Where can I get assessed for coloured lenses?
You will need to visit us at Brosgill Opticians, Street Lane, where we have the Intuitive Colorimeter test. You firstly need a full eye examination. This will check for any uncorrected refraction problems or any binocular anomalies. If found, these are corrected before proceeding with the use of colour.

How can I get coloured lenses?
The colour of the lenses can only be assessed by using The Intuitive Colorimeter, which uses a much larger range of colour combinations than used with the overlay assessment. This therefore gives a much more accurate colour specific to each patient. This is usually carried out by an Optometrist or Orthoptist and the test takes about 20 -30 minutes. When you wear glasses the whole of your visual field is coloured ie you are fully adapted to that colour. The Intuitive colorimeter takes account of this and tests in the same way so that no other colour of light is involved. Overlays on the other hand only cover part of your visual field therefore white light plays a big part. The colour of the lenses are hence different to that of the overlays due to the colour adaptation factor

What if overlays are helpful?
If the child continues to use the overlay, unprompted, or the teacher/parent reports an improvement it has most likely been beneficial. The overlay is usually given as a trial period for approx. 6 weeks to rule out novelty factors. Glasses with coloured lenses can then be prescribed. These are more convenient as they can be used with board work. The tint is a much more precise tint as many more colours combinations are used. Again the tint will vary from person to person.

What are coloured overlays?
Sheets of transparent coloured plastic, to be placed over the required text. Used as a screening tool to determine if colour will be of benefit to each patient. They can alleviate some of the visual stress, making reading more comfortable. Each child will benefit from a different colour.

Can adults be affected?
As people get older and text is not such a meaningless group of words, Visual Stress can be less pronounced, but still there. In a lot of cases the syndrome goes undiagnosed and untreated until adult life.

What are the signs of Visual Stress?
rubbing eyes
increased blink rate
poor concentration
using finger as marker
low self esteem

What are the symptoms of Visual Stress?
headaches when reading
movement/blurring of print
eye ache
rapid tiring

Is visual stress the same as Dyslexia?
Visual stress can be due to a number of conditions including Dyslexia, but is not the same.

What causes the Visual Stress?
The hypothesis is that the stress is due to a hyper excitability of the neurons in the visual cortex, an area of the brain at the back of the head, which fire inappropriately. In other words these cells kind of work a bit too fast which causes the disturbances in the text.

What is Visual Stress?
A condition contributing to reading difficulties, eye strain and headaches when reading. It can be responsible for light sensitivity, appearance of patterns in the text and glare effect.

Source: British Dyslexia Association

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