Sheffield Dyslexia Centre

Teaching, Supporting, Assessing

Letter re visual difficulties Sheffield Dyslexia Centre

September 2021

Dear Parents, 

A few of you have asked about the professional guidance from SASC (Specific Learning Difficulties (SpLD) Assessment Standards Committee) provided to specialist assessors of specific learning difficulties in relation to possible co-occurring visual difficulties.

(These assessors are the professionals who can diagnose dyslexia and other specific learning difficulties and are suitably qualified  pychologists or specialist teachers).

This guidance highlights misinformation and problematic practice in relation to visual difficulties.

It is important to note that:

Dyslexia is a learning difficulty that primarily affects the skills involved in accurate and fluent word reading and spelling. Characteristic features of dyslexia are difficulties in phonological awareness, verbal memory and verbal processing speed (from the governmental Rose Report, 2009 p.11).

Therefore visual difficulties are not a feature of dyslexia which is due to difficulties with processing auditory information.

Although more detailed information about the guidance provided may be obtained from:

Useful extracts from these documents are:

‘There is an unproven association between visual stress and dyslexia’

 ‘If there are concerns that a person has any sort of visual difficulties, there must be a referral to a suitably qualified optometrist, ophthalmologist, orthoptist or optician who can assess for refractive error (myopia, hyperopia and astigmatism), oculomotor dysfunction (focusing and eye coordination problems) and visual sensory anomalies (photophobia, pattern-related stress)

'Whatever training the SpLD assessor has undertaken, unless they are also a qualified optometrist, they cannot safely identify visual stress because they do not have the training and experience to first rule out a range of other possible explanations for the visual discomforts and disturbances experienced by the person assessed. Only qualified vision professionals can do this.’

The guidance also discusses the criticisms of the work of Irlen around the so-called Irlen syndrome. Serious problems are highlighted around:

  • 'the lack of peer-reviewed, evidence-based research to underpin (Irlen’s) claims for the existence of Irlen or scotopic sensitivity syndrome'
  • ‘over-inflated claims (Irlen 2010)3, not supported by research evidence, that a range of conditions, including ADHD, autism, chronic fatigue syndrome, epilepsy, Tourette's, head injuries, agoraphobia, anxiety attacks, depression and conduct disorder could all be related to visual stress, either worsened by it or are actually misdiagnosed visual stress.)

SASC concludes that such criticisms ‘explain why Irlen's work and methodology remains marginal and is not considered by vision and many SpLD practitioners as acceptable mainstream practice.’

Assessors should not refer to Irlen or Meares Irlen syndrome or scotopic sensitivity.  Assessors should not conduct coloured overlay tests. Assessors should not diagnose visual stress,’

‘There is no strong evidence that someone with a SpLD is more likely to need to use a coloured overlay than anyone else.’

I do hope these are helpful but please contact us if you have any questions.

Best wishes,


Mel Hunt

Principal Specialist Teacher, Sheffield Dyslexia Centre (SDC)

Knowle House, 4 Norfolk Park Road, Sheffield, S2 3QE




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