Developmental Dyslexia Paper

This is a very clearly written and easy to follow paper about dyslexia, written by UK expert Professor John Stein from Oxford University.

We are featuring this paper for two reasons:

  • (1) Many with CVI have difficulties reading and writing, and it is not easy to understand where this fits in with the challenges people with dyslexia have with reading and writing.
  • (2) Professor Stein reviews the progress in understanding the difficulties known as dyslexia since it was discovered in 1878 and his reflections have important lessons for the CVI community.


Dyslexia, in terms of the difficulties it creates, poses challenges to or delays the development of reading or writing while - "leaving oral and non-verbal reasoning skills intact". This means that the child is considered intellectually typical for their age in terms of their language skills and development. Thus, a child who is considered to have general learning delay, affecting many areas of their development including their vocabulary and academic skills, would not be considered to have dyslexia as their learning difficulties explain the developmental delay in reading and writing.

This makes sense, because teaching approaches need to be specific to the needs of the child, and a child who is otherwise very able, would benefit from different teaching approaches to a child with considerable learning challenges.

Dyslexia was originally considered a visual processing disorder until the 1950's when the view that it was a phonetic disorder became popular. From the 1950s for sixty years, the understanding of dyslexia followed this single phonetic explanation, and other opinions about potential alternative causes were essentially disregarded (almost certainly to the detriment of innumerable children).

What does phonetic mean?

Phonetic, dictionary definition.Phonetic, dictionary definition.

To understand the phonetic explanation, try spelling out the word get as a child might, using lower case letters and sounding them out (either in your head or out loud) g.....e.....t...

It is that ability to sound out the letters both mentally or actually, that was considered to be absent or challenged in children with dyslexia - even though the same children had no known difficulties with overall language skills ("oral and non-verbal reasoning skills"). So, dyslexia fell under the jurisdiction of the linguists and educational psychologists, and moved away from the early theories considered by neurologists that there could also be visual processing reasons to explain the difficulties.

In this paper, Professor Stein challenges this view that dyslexia has a single phonetic cause, and lists many possible reasons why a child with typical language skills may have difficulties learning to read and write, including those relating to cerebral visual impairments.

One of the cerebral visual impairments we have focused on in relation to reading and writing difficulties is simultanagnostic vision, and we explain the challenges and suggest an approach to use, in our section Reading Using Whole Word Recognition. We have also developed the free reading tool Look to help specifically with these difficulties.

We developed the reading tool Look to help children affected by simultanagnostic vision with reading.We developed the reading tool Look to help children affected by simultanagnostic vision with reading.

What Professor Stein argues, is that we need to go back to before the 1950s and look at the different causes of dyslexia, so that once tested we can "set in motion a remedial programme tailored to each child's particular, individual, pattern of needs".

Professor Stein argues that we have to look at the cause, and understand that there are many different causes, and the child may be affected by a combination of these different causes, but the approach needs to reflect the specific individual needs of the child.

When only the phonetic explanation was considered, children who had different reasons for their reading and writing difficulties, unsurprisingly didn't respond to the teaching approaches aimed at phonetic difficulties. So what happened to the children who didn't respond to the incorrect approaches over those sixty years? Maybe they were simply considered to have other challenges that were most likely unknown, like a 'learning delay'.

At CVI Scotland we find terms like learning delay or learning difficulty often stop people thinking about what is causing the difficulties the individual child is facing.

Any single behaviour can have many different causes.

Regrettably, we still find that where children show a specific behaviour, it is often the behaviour that is treated, rather than the cause of the behaviour. Just like the reading and writing challenges of dyslexia (the behaviour) have for decades, been treated as having phonetic difficulties.

Think of these behavioural labels:

  • Non-verbal
  • Clumsy
  • Distracted
  • Learning delayed
  • Disruptive
  • Repetitive
  • Obsessive

All of these have many different causes, but so often the behaviour is treated reactively, without seeking out and dealing with the cause.

This is why increasingly we think labelling children by their behaviours is not necessarily in their best interest - identification of causes, and pathways to effective remediation are what is needed.

Labels entail groups which entail generic approaches.  Look at the child and the individual causes of their challenges then create an approach specific to the child, not a label.Labels entail groups which entail generic approaches. Look at the child and the individual causes of their challenges then create an approach specific to the child, not a label.

The Cause.

Imagine having a cough - what are some of the different causes:

  • Maybe a little fluid has gone into your windpipe and you are coughing it out?
  • Maybe you have a cold virus?
  • Maybe you have a chest infection?
  • Maybe you are having an allergic reaction?
  • Maybe you have pneumonia?
  • Maybe you have lung cancer?

Could you imagine going to the doctor with a cough, and all coughs being treated the same?

Doctors look for the cause of the cough, and this may take a little trial and error, being aware of the more serious conditions but ruling our the milder ones. When they figure it out, they treat the cause as best as they can and the patient hopefully recovers.

It's the same with most medical conditions - think about a sore back, headache, feeling of nausea, dizzy spells, skin conditions - each and every one has multiple causes, and the key to treatment is to match the right cause with the symptom / behaviour.

When a doctor treats a patient, with a couch for example, the look for the cause of the cough, and do not treat every cough as having the same cause.When a doctor treats a patient, with a couch for example, the look for the cause of the cough, and do not treat every cough as having the same cause.

This is what Professor Stein is saying about dyslexia, and is what we say about the CVIs.

Facial Recognition is a good example, and it can be caused by:

Or any combination of these, as well as other issues such as problems with memory.

Similarly, for children with CVI reading and writing can be difficult for many reasons (see list below). The approach to help a child with reading and writing difficulties who has simultanagnostic vision, is different from the approach for a child with low visual acuity. Where the child has both simultanagnostic vision and reduced acuity, it is different again. We need to understand the causes of the difficulty, and match the educational methods to them.

For example a label of 'low vision and additional needs' means that each cause of low vision, and each specific need must be looked for, found and dealt with.

CVI & Dyslexia

According to this paper, CVI is a known cause of dyslexia, but only where the child has typical language skills.

This means that the child with CVI with developmental delay affecting both language skills as well as reading / writing skills is not considered to have dyslexia.

So dyslexia can be due to CVI, but not if the CVI and associated brain injuries have led to global developmental delay. (Nevertheless, it is important to profile the child's vision to make sure that all learning material can be seen.)

Paper: What is Developmental Dyslexia? John Stein, Brain Sciences 2018

CVI & Reading

CVI can interfere with reading in many ways, below we have listed a few examples with suggested approaches:

Low visual acuity
Limits the size of print a child can see. Please see our section on Font Sizes for more information.

Visual field impairments
Can obstruct the flow of reading to left, to right and down below. Turning the page sideways or to an angle can help,

Dorsal Stream Dysfunction
Can obstruct access to read if the print is too small and crowded for the child to see it easily enough, or if there is a busy, cluttered or noisy environment. Please read our section Reading Using Whole Word Recognition for more information.

Ventral Stream Dysfunction
Can cause impairment of recognition of words / letters. The child may need more time to match words with what they are, and more time to recognise them when seen.

Disturbances of eye movements, related to CVI, can also interfere with reading, and may need to be characterised and understood.


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At CVI Scotland we are devoted to helping people understand cerebral visual impairments, and together working towards developing the understanding of this complex condition.