Assistive technology and tools 
for learning difficulties, migraines 
and other neurological differences 
 

 

 

Research

Over the past 30 years, there has been extensive research into Visual Stress and its treatment with coloured filters. Performed originally under the name Scotopic Sensitivity Syndrome (a misnomer) and Irlen Syndrome, researchers have named the condition Meares-Irlen Syndrome, Meares-Irlen Syndrome/Visual Stress (MIS/ViS), Pattern Glare, Pattern-Related Visual Stress (PRVS), or simply, Visual Stress.  As awareness and a fuller understanding of the condition has grown around the world, thanks in large part to the initiative of Helen Irlen, other researchers including Arnold Wilkins, Bruce Evans and Jie Huang have initiated their own studies, offering additional supporting scientific evidence for the condition and its treatment. 

 

Research has concentrated on defining the condition, clarifying the symptoms, determining the origin, identifying the triggers, and developing the solutions.  The following research references are grouped by the areas of our understanding of Visual Stress today.  

 

1. Pattern Sensitivity:

Ocular discomfort often manifests when viewing certain image types, such as repetitive striped patterns1.1. The intensity of these effects will vary according to individual susceptibility and the precise nature of the pattern, most notably, its spatial frequency and contrast level1.2. An adverse response when viewing stimuli of this type, i.e., striped patterns, has been termed patterned glare1.3, and later pattern glare1.4.

1.1.  Visual stress. Oxford University Press, Oxford - Wilkins, A.J. (1995) [ Link  ]   

1.2.  A neurological basis for visual discomfort. Brain 107:989–1017 - Wilkins AJ, Nimmo-Smith I, Tait A, McManus C, Della Sala S,Tilley A, Arnold K, Barrie M, Scott S (1984) [ Link  ].   

1.3.  On the reduction of eyestrain when reading. Ophthal Physiol Opt 4:53–59- Wilkins AJ, Nimmo-Smith I (1984)) [ Link  ]   

1.4.  Tinted lenses and related therapies for learning disabilities: a review. Ophthal Physiol Opt 11:206–217- Evans BJW, Drasdo N (1991) [ Link  ]   

1.5.  Evans, B.J.W. & Stevenson, S.J. 2008. The Pattern Glare Test: a review and determination of normative values. Ophthal.Physiol.Opt., 28, 295-309  [Link]   

 

2. Symptoms of Visual Stress:

 

For susceptible individuals, this sensitivity to pattern glare can result in visual stress, giving rise to symptoms of eyestrain, headaches and glare, along with illusions of colors, shapes, and motion2.1.

 

2.1.  On the reduction of eyestrain when reading. Ophthal Physiol Opt 4:53–59- Wilkins AJ, Nimmo-Smith I (1984)) [ Link  ]   

 

3. Origin of Visual Stress:

 

The characteristics of the visual stimulus, which cause (or at least contribute in generating visual stress) is sensory in origin3.1 and therefore distinguishable from factors of motor origin, such as oculomotor balance, binocular vergence, and accommodation3.2. The origins of pattern glare and visual stress is thought to arise due to cortical hyperactivation3.3-3.6.

 

3.1.  A neurological basis for visual discomfort. Brain 107:989–1017 - Wilkins AJ, Nimmo-Smith I, Tait A, McManus C, Della Sala S,Tilley A, Arnold K, Barrie M, Scott S (1984) [ Link  ]  .

3.2.  Binocular vision, age and symptoms. Ophthal Physiol Opt 9:115–120 - Yekta AA, Pickwell LD, Jenkins TCA (1989)  [Link] 

3.3. fMRI evidence that precision ophthalmic tints reduce cortical hyperactivation in migraine. Cephalalgia 31(8):925–936 - Huang J, Zong X, Wilkins A, Jenkins B, Bozoki A, Cao Y (2011)  [Link] 

3.4.  Some visual, optometric and perceptual effects of coloured glasses. Ophthal Physiol Opt 1:163–171 - Wilkins AJ, Neary C (1991)   [Link] 

3.5.  The optometric correlates of migraine. Ophthal Physiol Opt 24:369–383 - Harle DE, Evans BJ (2004)  [Link] 

3.6.  Visual stimuli are common triggers of migraine and are associated with pattern glare. Headache 46:1431–1440 - Harle DE, Shepherd AJ, Evans BJ (2006)   [Link] 

 

4. Triggers of Visual Stress:

 

The visual perceptual distortions that are generated by susceptibility to pattern glare is maximal when the spatial frequency of the stimulus is around three cycles per degree, with a pattern of even width and spacing, high contrast and viewed binocularly4.1, 4.2. Many of the attributes necessary to generate pattern glare in the susceptible individual are present within standard text documents formed by the individual rows of words separated by the successive spacing between rows4.3-4.5. The spatial frequency of this alternating high contrast pattern, formed by text, has been shown to fall within the range known to generate pattern glare symptoms4.6. This is coupled with striped patterns formed by letter strokes in individual words, as well as the vertical strokes of letters that also have a spatial frequency falling within a range sufficient to generate pattern glare symptoms in susceptible individuals.

 

4.1.  Visual Stress. Oxford University Press, Oxford - Wilkins, A.J. (1995). [Link]   

4.2.  A neurological basis for visual discomfort. Brain 107:989–1017 - Wilkins AJ, Nimmo-Smith I, Tait A, McManus C, Della Sala S,Tilley A, Arnold K, Barrie M, Scott S (1984).  [Link]   

4.3.  On the reduction of eyestrain when reading. Ophthal Physiol Opt 4:53–59- Wilkins AJ, Nimmo-Smith I (1984). [ Link  ]   

4.4.  Reading and visual discomfort. Visual processesin reading and reading disabilities. Erlbaum Associates, Hillsdale, NJ - Wilkins AJ (1993).  [Link] 

4.5.  The clarity and comfort of printed text. Ergonomics 30(12):1705–1720 - Wilkins A, Nimmo-Smith I (1987).  [Link] 

4.6.  Visual stress theory and its application to reading and reading tests. J Res Read 27:152–162 - Wilkins AJ, Huang J, Cao Y (2004).  [Link] 

 

5. Solution Options for Reducing Visual Stress:

 

A large volume of research provides evidence that colour filters reduce Visual Stress. In 1994, while a t the Medical Research Council Applied Psychology Unit in Cambridge UK, Arnold Wilkins invented the MRC Intuitive Colorimeter and Precision Tints.  This facilitated one of the best known studies into visual stress5.1

 

5.1.  Double-masked placebo-controlled trial of precision spectral filters in children who use coloured overlays. Ophthal.Physiol.Opt., 14, 365-370 - Wilkins, A.J., Evans, B.J.W., Brown, J., Busby, A., Wingfield, A.E., Jeanes, R., & Bald, J. 1994.  [link]  

5.2.  Scotopic sensitivity/Irlen Syndrome and the use of coloured filters: a long-term placebo-controlled and masked study of reading achievement and perception of ability. Perceptual & Motor Skills, 88, 83-113. - Robinson, G.L. & Foreman, P.J. 1999.  [link]  

 

Studies have also found that the optimal colour needs to be individually prescribed, and sometimes with considerable precision5.3, 5.4   

 

5.3.  How precise do precision tints have to be and how many are necessary? Ophthalmic and Physiological Optics, 25, (3) 269-276 - Wilkins, A., Sihra, N., & Nimmo-Smith, I. 2005.   [link]    

5.4.  Both coloured overlays and coloured lenses can improve reading fluency, but their optimal chromaticities differ. Ophthal.Physiol.Opt., - Lightstone, A., Lightstone, T., & Wilkins, A. 1999. 19, (4) 279-285.  [Link]   

 

6. Additional Resources:

 

6.1.  Visual Aspects of Dyslexia. John Stein and Zoi Kapoula, Editors.  (2012) Oxford University Press  [Link]  

6.2.  Vision Rehabilitation.     [Link]  

6.3   Vision and Reading Difficulties. Ten Alps Creative, London - Allen, P.M., Evans, B.J.W.,  Wilkins, A.J. (2009)  [Link]    

6.4.  Reading Through Colour. Wiley, 1 edition Wilkins, A.J. (2003).  [Link]  

6.5.  The Light Barrier. Stone, Rhonda (2003)

6.6   Reading by the Colors. Irlen, H (2002)  [Link]  

6.7.  Dyslexia and Vision. Evans, BJW (2001)  [Link]   

6.8   Visual Stress. Oxford University Press, Oxford - Wilkins, A.J. (1995). [Link]   

 

 

The majority of the text in this document comes from the Introduction to “Susceptibility to pattern glare following stroke” by I.G. Beasley and L.N. Davis and published in the Journal of Neurology (2012) 259:1832-1839  [Link]  

 

For more information on the individual researchers, please refer to “Key Researchers” and “Key Research Institutions”, or the [links] section of our website.