01 May 2014

BY: Louise Hilliar

In this post I aim to outline the nature of visual stress, briefly discuss methods of identification and treatment, and point the reader towards further sources of information, as well as indicating where appropriate help may be sought.

When I heard that the actor, Paddy Considine who has starred in films including Hot Fuzz and Dead Man’s Shoes experiences visual stress, I immediately found out more about him. This is because I am aware that visual stress is more common in those with neurodiverse conditions than the rest of the population. I soon discovered that Considine is also said to have been diagnosed with Asperger Syndrome.

When I meet a client who may have a neurodiverse condition, I am always aware that they may also experience visual stress. It’s important to identify this condition and to provide advice about how it can be addressed. The signs can be fairly obvious, for example when someone enters the room wearing dark glasses or asks for lights to be turned off.  On the other hand, they may be more subtle, for example when someone needs to use a guide to keep their place when reading. There may be no obvious signs of visual stress during an assessment, and I often only become aware that a client may have visual stress by asking particular questions about their experience of reading.

The symptoms of visual stress were identified in the early 1980s by two people working independently of each other and unaware of each other’s work. They were Olive Meares and Helen Irlen. Both had found that visual perceptual difficulties experienced when reading appeared to be alleviated through the use of coloured overlays placed on the page.  Helen Irlen went on to experiment with coloured lenses and set up Irlen Institute whose centres are licensed to supply the coloured lenses that she devised. A description of her work can be found in her book entitled ‘The Irlen Revolution’.

In his book, ‘Reading Through Colour’ Arnold Wilkins describes himself as the scientist responsible for developing the idea of visual stress as a neurological disorder. He claims that visual stress occurs when some nerve cells in the visual cortex of the brain fire too strongly and cause others to fire when they should not. Professor Wilkins reports that the symptoms of visual stress are often evident when reading and that these often include:

  • movement of print
  • blurring print
  • letters changing size
  • doubling of letters
  • letters fading or becoming darker
  • patterns appearing in print or ‘rivers’ appearing to run through text
  • illusions of colour
  • nausea, dizziness, discomfort or even pain, associated with glare


Professor Wilkins has found that as well as reporting some of the above experiences, those with visual stress may show physical signs such as:

  • moving closer or away from the page and frequently changing position when reading
  • often looking away from the page
  • yawning
  • tracking text with their finger
  • rubbing their eyes
  • blinking excessively
  • reading slowly or hesitantly


Importantly, Professor Wilkins points out that these signs and symptoms may be due to factors other than visual stress such as:

  • refractive error (corrected with glasses)
  • difficulty adjusting focus
  • difficulty coordinating the two eyes (often treated with eye exercises)


He says that, for this reason, it is essential that anyone who experiences these signs and symptoms consults an optometrist or orthoptist.

Professor Wilkins acknowledges that Helen Irlen’s discovery was significant but also refers to concerns which have been raised in relation to her work on the basis of its commercial emphasis and because Irlen diagnosticians are not trained optometrists. He highlights the importance of evaluating new treatments in a scientific manner and of discovering why they work. In return, the Irlen Institute cites evidence which undermines Wilkins’ methods and the equipment that he has developed.

The symptoms of visual stress may be reduced through the use of coloured overlays which can be purchased freely via the internet. It is important to pin-point the precise overlay that works for you, however, and therefore it is advisable to consult a professional with experience in this area. This could be an optometrist (the most common type of eye care professional), a behavioural optometrist (specialist optometrists who focus on the ways in which visual problems affect human performance) or an orthoptist (based in hospitals and investigate, diagnose and treat defects of binocular vision and abnormalities of eye movement). Alternatively, it could be an Irlen Screener, Irlen Diagnostician, teacher, or psychologist.

Wilkins describes a procedure for selecting overlays which could be used by a range of professionals. This method is based on the Intuitive Overlays which he developed and are supplied by iOO Sales. It can be readily adapted for use with Cerium Overlays which are similar and are supplied by Cerium Visual Technologies. Helen Irlen takes a different approach and stresses the importance of undergoing a screening process with a trained screener. Irlen overlays are available to purchase from providers such as dyslexic.comCrossbow Education also produces coloured overlays as well as a Visual Stress Assessment Pack.

If you benefit from using coloured overlays, then you may like to consider the use of tinted glasses. These can be helpful when reading from a distance and may also help with writing. The colour of glasses can be chosen more precisely than the colour for overlays which means that better results can be achieved in terms of reducing the impact of visual stress. Wearing tinted glasses does not usually mean that individuals see their environment in a different colour.

The Intuitive Colorimeter was developed by Arnold Wilkins. It is a machine that illuminates a page of text with coloured light. The light can be adjusted according to hue, saturation and brightness and therefore any shade of colour can be selected. With the support of a computer program, coloured trial lenses are made up to match the selected shade of colour. The patient tries out the trial lenses under a variety of light sources and lighting intensities and once an acceptable combination of trial lenses has been chosen, the tinted glasses are ordered.

The system used by Irlen Diagnosticians to select tinted glasses or ‘Irlen Spectral Filters’ involves the use of a lens kit which contains each colour in the spectrum and allows colour combinations to be created which suit the individual. The diagnostician establishes which part of the light spectrum needs to be filtered and the extent to which it needs to be filtered. Once the individual’s optimal colour has been determined, they try out the lenses in a range of situations including reading and looking at a computer monitor.

The use of coloured overlays and tinted glasses are among a series of measures that can be implemented to make life easier for many of the clients that I meet through my work.

You may like to find out more about Professor Wilkins’ work and about the work of the Irlen Institute.

Detailed information about who you can approach for an assessment for visual stress can be found on the British Dyslexia Association website.