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Q: What is Visual Stress?

Visual Stress is a neurological condition contributing to reading difficulties, eye strain and headaches. It can be responsible for light sensitivity, perceptual processing difficulties and the appearance of patterns in the text.

Q: What causes Visual Stress?

The hypothesis is that the stress is due to hyperexcitability of the neurons in the visual cortex, an area of the brain at the back of the head responsible for visual processing. The brain works inefficiently which leads to problems with processing and perception.

Q: What are signs of Visual Stress?

The main signs are

  • eye rubbing;

  • increased blink rate;

  • light sensitivity;

  • poor concentration;

  • using a finger as a marker; and

  • low self-esteem.

Q: What are the symptoms of Visual Stress?

The main symptoms are

  • glare;

  • headaches when reading;

  • headaches in bright areas;

  • movement/blurring of print;

  • eye ache; and

  • rapid tiring.

Q: Can adults be affected?

As a child, text often appears like a meaningless group of words. As they get older and their vocabulary increases and they understand more about the structure of text, Visual Stress can be less pronounced, but still there. In a lot of cases, the syndrome goes undiagnosed and untreated until adult life. 

Q: 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-Irlen Syndrome, Irlen Syndrome or, incorrectly as, Scotopic Sensitivity Syndrome. 

Q: What are coloured overlays?

They are sheets of transparent coloured plastic, to be placed over the required text. Used as a screening tool to determine if the colour will be of benefit to each patient, they can alleviate some Visual Stress symptoms, making reading more comfortable. Every individual will benefit from a different colour. In order to assess the benefit of the chosen colour, the Wilkins Rate of Reading test should be carried out.

Q: Do children need coloured overlays or coloured glasses permanently?

It seems that children benefit the most from colour if offered as soon as any reading difficulties are suspected, before the cycle of failure has begun. According to research, many 7-year-olds appear to use coloured overlays for a year or two and then discard them as they become unnecessary. This may be because the acquired familiarity with text makes the distortions less distracting.

Q: How can I get coloured lenses?

Through an Intuitive Colorimeter™ assessment!

The colour of the lenses can only be assessed through the Intuitive Colorimeter™ assessment. It uses a large range of colour combinations, compared to the overlay assessment, giving an accurate lens colour specific to each patient. 


The assessment is carried out by an eye care professional and takes approximately 45 minutes.


When you wear glasses your field of view is coloured. 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 field of view. Therefore, white light plays a big part in your field of view.  The precision tinted colour of the lenses are often different from an overlays due to the light registered from your field of view.

Q: Where can I get assessed for coloured lenses?

Visit one of Opticalm’s Intuitive Colorimeter™ assessment providers.

Before getting an assessment with a colorimetry provider, you will need a full eye examination to check for any uncorrected refraction problems or any binocular anomalies. If found, these are corrected before proceeding with the use of coloured glasses. 

Q: Are coloured glasses necessary?

If an individual suffers from Visual Stress then precision tinted lenses would be recommended.  Individuals who persist in using overlays usually find coloured glasses more convenient to use. Glasses can help with writing, whereas overlays cannot. The degree of precision in the choice of colour is critical for obtaining the best results, and the precision available with lenses is far greater than with overlays.

Q: What tests should I expect the optometrist to do?

The precise routine will vary from one optometrist to another. However, 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 an optometrist whether they would do the following tests before you book an appointment. 


  • Mallett fixation disparity test at near.

  • Fusional reserves at near.

  • Accommodative lag. 

  • Coloured overlay testing.


Note that not all optometrists who have specialized in this subject have an Intuitive Colorimeter™, but all should know of a colleague who they can refer you to if this further testing is needed.

Q: 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 that 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  due to the eyes but the visual cortex part of the brain. Colour is likely to help in these cases.


Frequently asked questions

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