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Phone Number: 01603 704040
Fax Number: 01603 704047
Minicom Number: 01603 704044
Email: sensorysupport@norfolk.gov.uk

Visual Stress

Visual Stress/Meares Irlen Syndrome

Assessment for Meares Irlen Syndrome

What is visual stress (Meares Irlen Syndrome?)



Visual Stress, also known as Meares Irlen Syndrome, is thought to occur when visual information is processed in the visual cortex.  The symptoms most frequently reported are print distortion and rapid fatigue when reading, with associated poor tolerance to glare, frequent headache and eye discomfort.  In individuals who are susceptible to visual stress   there appears to be a sensitivity  o gratings (striped patterns), especially in high contrast. (Thus as print becomes smaller and more closely spaced it becomes a grating and increasingly problematic). Visual stress is not a problem with the functioning of the eye itself and the symptoms do not respond to conventional optometric treatment.  However many people who experience visual stress find that coloured filters (overlays) or precision tinted lenses eliminate or reduce their symptoms and allow them to read for longer and in greater comfort.  Other simple modifications in the classroom such as using coloured paper, changing the background colour of a computer screen or spacing writing on the board can also be helpful.


The colour which helps seems to be specific to individuals and people need different colours for their overlay or lenses.  The colour that a person requires needs to be chosen with precision, sampling a large number of colours comprehensively and systematically


What are the symptoms of visual stress?


  • movement of print – vibration, shifting side to side or up and down; words breaking up; words joining up; letters muddling; three dimensional movement, movement of surrounding words; movement of words at the beginning and end of lines; words seeming to fall off the page.
  • blurring of print – print which is small and closely spaced causes most problems.  High contrast black ink on white paper is often visually stressful.  Print often appears clear when first looked at and the distortions increase in severity as the student continues to read.  Sometimes looking away or closing the eyes will clarity, but this improvement is usually short lived.
  • letters seeming to change size.
  • doubling of letters, extra letters appearing at the end of words.
  • letters fading, becoming darker or flashing.
  • patterns appearing in the dark print or the white spaces.
  • illusions of colour - blobs of colour moving across the page, distracting the reader or obscuring words; highlights around letters or words, (sometimes these extend to auras of light or rainbows around people and objects.)
  • tiredness; nausea; dizziness; eye discomfort or even pain.
  • frequent headaches 


What happens at the assessment carried out by Virtual School Sensory Support?

An assessment is only carried out after an examination by a health care professional (optomatrist/ophthalmologist) has eliminated problems with the eye by examining refraction, binocular vision, accommodation, colour vision etc..

Aim of the assessment:

  1. to determine whether a further examination by an eye care professional is required to exclude conventional optometric problems
  2. to determine whether the young person has a problem with visual functioning 
  3. to determine whether he or she is experiencing symptoms of visual stress
  4. to determine whether he or she benefits from using a coloured overlay when reading
  5. to find the colour which is most effective in increasing clarity and comfort
  6. to inform  family members and teachers about the kind of difficulties the student is experiencing and suggest classroom management techniques which may help 


Before assessment it is essential that the young person should have an optometric examination (carried out by an optometrist) to rule out other causes of visual symptoms e.g. a problem with refraction or binocular vision.


During the assessment:

Students will be asked about their history and will be asked to describe visual difficulties in detail, looking at the different problems that may occur during the course of the school day.  This is to find out whether the student experiences visual stress when looking at print in different contexts, for example in a book, on a computer screen, on a white or interactive board, when reading music or looking at graphs and squared paper etc.  


The assessment will include certain tests and activities designed to indicate whether there is a problem with the functioning of the eye or with the development of visual functioning skills which are causing problems which are not caused by visual stress, as well as specific tests designed to identify susceptibility to visual stress.


Tests administered during the assessment may include the following:

General Tests for visual acuity and visual functioning:

  1. MacLure Reading Type for Children – shows the smallest print a student is able to read and indicates which is the smallest print size where reading may be sustained for some time in comfort.  This is a test of near vision.
  2. Kay pictures – test of near vision using pictures rather than letters.
  3. Snellen acuity test – test of distance vision using letters of decreasing size in strong contrast.
  4. Barraga Test of Visual Functioning Efficiency – a general screening tool which examines visual functioning i.e. shows how a person uses their vision and interprets visual information.  It involves pictures and letters.
  5. Tracking exercises –to assess speed and efficiency of tracking through lines of letters presented in random order.
  6. Tests from the Development of Visual Perception Assessment (DVPS 2nd edition)  – used to assess hand/eye co-ordination – including the ability to draw lines between targets and to recognise the features of drawings or patterns and to reproduce them with accuracy.
  7. Tests for colour vision e.g. Waggoner colour plates, city vision.
  8. Tests for stereopsis (binocular vision and ability to see in 3D) e.g. Langstereo test, Stereo Fly Test.
  9. Goodenough Draw a Person Test: test for development gives maturity age
  10. Cardiff Contrast Sensitivity Cards: measures contrast sensitivity


Tests for Visual Stress:

  1. Rate of Reading Test:  the young person reads list of common words presented at random.  The print is small and closely spaced, causing visual stress in a short time in people who are susceptible.  The test is used to determine whether symptoms of visual stress occur and to measure reading speed with and without an overlay. 
  2. Selection of overlay – the overlays are placed over text, compared in twos, side by side, and the optimum colour is obtained by process of elimination.
  3. Perception of a picture composed of repeated symbols – useful for determining symptoms and benefits of overlay in non-readers.
  4. Institute of Optometry Pattern Glare Test – examination of grid patterns designed to indicate symptoms of visual stress.
  5. Students are asked to read conventional text which is within their reading capability, with and without an overlay, to make a subjective assessment of the use of colour. 

The assessment is not an examination/test and is not usually found to be emotionally stressful for the young person although people who are susceptible to visual stress may experience a headache or visual discomfort after attempting the assessment tasks.


What happens after the assessment?


If the student demonstrates signs and symptoms of visual stress and benefits from using an overlay he or she will be issued with an overlay to use consistently for all reading tasks for the next six weeks or so.  This is a diagnostic test and will confirm whether an overlay continues to be of benefit in a practical setting.

A report setting out the results of the assessment tasks and suggesting recommendations will be sent to the young person’s family, their school and to any other professional who is involved in their care.

Routine follow up is not arranged but the young person’s family and teachers are asked to monitor him or her and to report back to Virtual School Sensory Support after six weeks of overlay use if there are any concerns. 

If a student is still using the overlay willingly after at least six weeks and is finding it beneficial, it is likely that he or she will find precision tinted lenses more convenient to use.   Virtual School Sensory Support staff are unable to prescribe or finance the purchase of lenses.  Lenses need to be obtained using a system that tests with a wide range of colours and allows the required colour to be precisely specified and checked. The Intuitive Colorimeter is recommended and a list of optometrists with this equipment may be obtained from Cerium Technology.  It is important not to tint lenses to match the overlay as the best colour for overlays is NOT the same as for precision tinted lenses.  On request Virtual School Sensory Support is able to provide contact details of qualified optometrists who use the guidelines set out by the British College of Optometrists to prescribe precision tinted lenses in Norfolk.


Assessment by Virtual School Sensory Support 

Assessment for Visual Stress takes place on receipt of a referral.  Referrals are taken from schools, parents/carers and other professionals e.g. health care professionals.

 The assessment usually takes place in a clinic at the Virtual School Sensory Support Base at The Sensory Support Centre, Woodside Road, Norwich NR7 9QL (tel. 01603 704040).  In exceptional circumstances the assessment will take place at the student’s own school (when this is necessary there may be a longer wait for the appointment).  Parents/carers/family members are always welcome, invited to be present and provide useful background information. 

The assessment usually takes between 30 minutes and one hour.  The only requirement is a desk for the assessor and student to work together and a quiet place where they may work without interruption.