The Visual Model of Reading

 
By Stuart Warren, MSc(Optom) (Hons)

 The majority of consensus is that reading problems such as dyslexia are due to
difficulties converting the visual components of words into their sound components.
Vellutino, Fletcher, Snowling, Scanlon (2004)
 Consider the word “cat”…
c / a / t > “c” / “a” / “t”
 The visual components are called “graphemes” & the sound components are called
“phonemes”.
 There are about 44 phonemes in the English language.
 Difficulty making this conversion underlies the “Phonological Model” of reading.
 This can be helped by teaching phonemic awareness (word sounds) and phonics
(mapping sounds to letters or parts of words).

 Research by Professor Sally Shaywitz at Yale University using fMRI brain scans on
students with dyslexia has shown numerous areas of the brain are involved in reading
but that there are 3 areas in the left hemisphere that dominate. Shaywitz et al (1998).
These include a Visual Word Form Area (yellow), a Word Analysis Area (red) and a
Speech Area (green).
(Front) (Back)

 The Word Analysis Area (WAA) is located in the temporal parietal cortex.
 The Visual Word Form Area (VWFA) is located in the occipital cortex.
 The speech area, also known as Broca’s Area, is located in the frontal cortex.
 The WAA is important for phonological processing and works together with the speech
area for saying words. It is the slower “sub-lexical” route important for decoding words.
 The VWFA is important for storing words that have been added to our sight word
vocabulary and also works together with the speech area for saying (or subvocalizing)
words. It is the faster “lexical” route for normal reading.
 These areas comprise the key neural circuits for reading.
 Other areas in the brain important for
reading include the Auditory Cortex
for processing auditory information
and Wernicke’s Area for language
comprehension.

 Although the evidence shows that phonological skills correlate the most highly with
reading disabilities this does not prove it is the cause. Castles & Coltheart (2004)
 Phonics training helps with non-word reading skills, word accuracy and letter-sound
knowledge but may not be helpful for reading fluency, spelling, phonological output
and reading comprehension. McArthur et al (2012)
 Not all students with dyslexia have a phonological problem.
 Not all students who require learning support have a reading problem.
 If other factors are shown to be deficient further upstream (such as vision) this
weakens the phonological model as being a cause for learning disabilities.
If a school phonics programme is successful is this because students have learned
better phonological skills or because they have developed better word identification
skills associated with the phonics programme?

 Vision is the dominant sense
 The symptoms suggest it
 Reading starts with vision
 The science shows a problem
 Visual interventions are effective

 It is estimated that at least 80% of learning is derived from vision.
 Try closing your eyes and think about all you couldn’t do in the classroom!

 When most children start school they are fine with mapping sounds to pictures &
objects. The same part of the brain however is also believed to be used for written
language (referred to as “neuronal recycling”) which suggests that the problem of
written language may be more to do with processing of visual symbols (ie. letters and
numbers).
 Young (or impaired) readers need bigger text and wider spacing.
 Losing place, skipping words and lines is common.
 Words appear to move on the page for some readers.
 Missing the start or ends of words is common.
 Persistent letter reversals.

Consider the visual skills required for reading. A reader needs to:
 Estimate the number of letters in a word (eg. a 2 or 5 letter word?)
 Position their eyes in the correct position on the word (about a third of the way along
the word).
 Keep the words stable on the page.
 Extract multiple letters per look (eg. 2 letters, 4 letters etc)
 Ensure the correct orientation and order of the letters.
 Identify the exact shape, colour and detail of the letters.

These visual skills can be describes as follows:
 Estimate the number of letters in a word – “visual counting”
 Position eyes in the correct position on the word – “saccades” or “voluntary eye
movement control”
 Keep the words stable on the page – “fixation”
 Extract multiple letters per look – “visual span”
 Ensure the correct orientation and order of the letters – “spatial attention”
 Identify the exact shape, colour and detail of the letters – “visual acuity”

But there’s a problem….
 Estimate the number of letters in a word – “visual counting”
 Position eyes in the correct position on the word – “saccades” or “voluntary eye
movement control”
 Keep the words stable on the page – “fixation”
 Extract multiple letters per look – “visual span”
 Ensure the correct orientation and order of the letters – “spatial attention”
 Identify the exact shape, colour and detail of the letters – “visual acuity”
When children’s eyes are tested at school only the skills at the
bottom in grey (“visual acuity” and “colour vision”) are tested.
The skills shown above in blue are NOT included however these
are the ones thought to be a problem with reading! They also
happen to be supported by the same neural pathways – the
“Magnocellular Pathway”.

 The science shows there are 2 main visual systems referred to as the “Magnocellular
Pathway” (M-Pathway) and the “Parvocellular Pathway” (P-Pathway).
 Both of these pathways originate from the eyeball and extend all the way to the back
of the brain called the “visual cortex” & remain anatomically separated.
What Do these Pathways Do?
 M-Pathways: make up only 10% of the visual
pathway but are much bigger in size. They
conduct information more quickly and are
important for motion, spatial coding and
temporal (rapid) processing.
 P-Pathways: make up much of the remaining
visual pathway and are smaller in size. They
conduct information more slowly and are
important for high contrast, colour vision and
fine detailed (static) processing.

 Only one system however, the M-Pathway, has been found to be a problem in dyslexia.
 The M-Pathway has been studied by scientists for over 30 years. It is much easier to
study BEFORE it reaches the visual cortex (at a “subcortical level”) as it is anatomically
distinct from the P-Pathway. Livingstone, Rosen, Drislane, Galaburda (1991)
 Examples of tests used to look for an M-Pathway deficit are:
 coherent motion sensitivity
 critical fusion frequency
 contrast sensitivity
 anatomical appearance
There are over 300 studies on the Magnocellular Pathways with 90% of them showing
a problem in dyslexia. This has become known as the “Magnocellular Deficit Theory” of
dyslexia.

 Once the M-Pathways & P-Pathways reach the primary visual cortex (V1) they diverge
in two separate directions.
 The P-Pathways track down to follow the “Ventral Pathway”. This has an input into the
VWFA.
 The M-Pathways track up to follow the “Dorsal Pathway”. This has a large input into
the WAA in the Parietal Cortex and continues through to the Frontal Cortex - the
region of the brain that controls voluntary eye movements for reading.
(Front) (Back)

 The M-Pathway helps us to know “where” we are on the page and captures critical
information rapidly, co-ordinates this with voluntary eye movements, and determines
early characteristics of the letters including their spatial arrangement. This information
is combined with information from the P-Pathway in order to identify “what” the letters
are.
 In addition to feedforward pathways (blue) there are also many feedback pathways
(red) which makes the M-Pathways harder to study at the cortical level.
(Front) (Back)

 In order to test for an M-Pathway deficit at the cortical level we need to consider the
type of skill being tested and the region of the brain that’s involved. The use of fMRI
brain scans can help with this. Demb (1998)
 Skills supported by the M-Pathway include:
 Voluntary eye tracking (saccades)
 Spatial coding of letters
 Temporal processing tasks (eg. visual counting & visual span)
 Motion stability
 A high M-Pathway input to the Cerebellum means that a deficit could potentially also
affect visual motor co-ordination. Stoodley & Stein (2013)
 There is evidence an equivalent M-Pathway may exist for auditory processing as well.
 This creates the possibility of a pansensory deficit across multiple domains or there
may be a predilection for just one domain only (eg. eye tracking). Stein (2001)
A standardized battery of tests that target M-Pathway functions essential for learning
would be helpful for clinicians and educators.

 It is well known that students with dyslexia have an eye tracking problem (ie. they make
more backwards eye movements and pauses) but this has often been attributed to a
language problem rather than a primary eye disorder.
 This is because early studies found no problem with eye tracking known as “saccades”.
 The reason was they only measured saccade reaction times for students ages 10 to 13
years old.
 Research by Professor Burkhart Fischer at the Freiburg University shows that
saccade reaction times are only significant for younger and older students for the two
main types of saccades, “pro-saccades” and “anti-saccades” (see below).

 Furthermore, when testing using an anti-saccade strategy (ie. one that requires the
student to look the other way from the test stimulus) it can be shown that students
with dyslexia have a significant problem with eye movement control independently of
language. Fischer & Hartnegg (2000), Fukushima (2005), Bucci (2008)
Graphs: Fischer & Hartnegg (2000)

 Studies show that “pursuit” eye movements are also associated with learning difficulties
including dyslexia. Callu et al (2005), Eden, Stein, Wood (1994)
 This is often overlooked because we do not use pursuit eye movements to read.
 It is known however that pursuit eye movements can share similar (and sometimes the
same) neural pathways as saccades! Krauzlis (2005), Rosano et al (2002)
 Above: Pursuit eye movements in non-dyslexics compared to dyslexics using a Tobii
eye tracker. Presentation from Dr. Anikar Haseloff (2009), University of Hohenheim.

 This includes a skill called “subitizing” (the ability to know the number of items present
in a look) and also the ability to count larger numbers of items from memory.
 It requires students to say how many spots were flashed on a small central screen.
 This visual perceptual capacity tests our concept of “number” and can be deficient in
students with dyscalculia as well as in dyslexia.
 A problem with this task correlates strongly with students struggling to acquire basic
arithmetic skills but it can also affect reading since we estimate the number of letters
in a word when we read (see next slide).

 It has been shown by Fischer and Hartnegg that students with dyslexia & dyscalculia
have a problem with visual counting – both in terms of accuracy and reaction times.
Fischer & Hartnegg (2008)

 The “visual span” is our window of visual attention.
 The further we can attend to visual information per look the greater the visual span.
 There are a number of different methods used to test visual span (eg. Form Resolving
Field, the Trigram Method, Letter Strings).
 If only one item is presented to the side of fixation this places a relatively low demand
on visual attention and so may not be deficient in dyslexia.
 If more than one item is presented to the side (or if items are presented on both
sides) of fixation this places a higher demand on visual attention (as the information
must be processed in parallel) and is more likely to be associated with dyslexia.
Trigram Method Letter String Method

 Bosse et al (2007) found the number of dyslexic students with a visual span disorder
was at least as high as the number with a phonological disorder and that around 23%
had a visual span disorder alone.
 A reduced visual span in dyslexia is not due to phonological processing, short term
memory (using letter strings) or lack of reading experience. Bosse, Valdois, Tainturier
(2007), Lobier, Zoubrinetzky, Valdois (2012)
 There is a relationship between the visual span and reading speed. A smaller visual
span leads to slower reading speeds (see graph below). Kwon, Legge, Dubbels (2007)

 Slow reading speed is a hallmark of dyslexia. Tressoldi, Stella, Faggella (2001)
 Dyslexics often exhibit a reduced visual span and slow reading. Dubois et al (2010)

 Early studies of spatial awareness focused on “lateral preference” (handedness and
eye/hand dominance) as a basis for learning problems. Belmont & Birch (1965) found
that lateral preference was not significant but confusion of left & right side was.
 Studies show that poor readers make more letter and word reversals which may be
linked to visual spatial confusion. Boone (1986), Jordan & Jordan (1990), Badian
(2005)
 As a child gets older they can use various linguistic mechanisms (eg. phonological,
semantic and syntactic) as well as other external cues to compensate for a visual
spatial deficit that may be contributing towards letter reversals. Hence the reversals
may no longer be obvious but the underlying spatial problem may still exist and
continue to affect academic performance. McMonnies (1992)
 The Florida Longitudinal Project found perceptual-motor factors are more important at
predicting reading performance for primary school aged children whereas cognitive
factors become more important for older students. Fletcher, Satz (1980)
 To understand the role of visual spatial development on reading we can turn to brain
imaging techniques which have become a useful tool for studying the effect of spatial
encoding on letter features. Pammer et al (2006)

 It has been found that the more disrupted the spatial qualities of the text becomes the
more active the spatial region of the brain as shown by MEG neuroimaging. This
places a higher demand on the M-Pathway. A deficiency would therefore make it
more difficult to encode letter features.
Eg. 1: “hAvInG iNcOsisTeNt FoNt can severely disrupt reading speed”.
Eg. 2: The ‘Cambridge Effect’ shows us that “lteters can be a taotl mses and you
can still raed wothiut a porbelm”.
 The above statement is not exactly true since reading a page of text like this would
severely decrease reading speed, even for a good reader. It would also be very
difficult for someone learning to read!
Consider the difficulty that a dyslexic student (or beginner reader) may have with
phonological processing (converting graphemes to phonemes) if they have trouble
encoding the letters!

 In addition, poor readers and students with dyslexia (over the age of 8) are more likely
to fail on the “Clock Drawing Test” - a medically recognized test of spatial awareness.
Eden, Wood & Stein (2003)
 Although dyslexics are often thought to have superior spatial abilities, a study by
Winner (2001) involving multiple spatial tasks found that dyslexics performed the
same or worse on all tasks except for one when compared to non-dyslexics.
 Dyslexics do appear to have better “global visual spatial ability”. Karolyi (2003)
 It has been argued that dyslexia may be a problem of visuo-spatial attention caused
by a deficiency in the visual dorsal stream. Vidyasagar (2010)

 This is the ability to perceive differences in sound. It has been shown to be a problem
in dyslexia by numerous investigators and has been linked to problems with decoding
(phonological processing). Tallal (1980), Heiervang et al (2002), Wang et al (2010)
 Fischer and Hartnegg (2004) show a systematic difference for dyslexics compared to
controls in auditory discrimination, especially for “frequency” and “time order” tasks
(see next slide).
 This may have a greater affect on skills such as spelling (converting sounds to letters)
and following instructions rather than on reading (converting letters to sounds).

 Interventions to enhance the visual skills presented in this discussion usually involve
training in the form of daily exercises or the use of tinted lenses.
 The fact these skills undergo such a long development period (up until 16 to 17 years
of age) demonstrates significant plasticity.
 The following slides will consider some of the evidence…

 There are studies in recent literature to support that saccadic eye movements can be
trained. Dyckman & McDowell (2005), Kveraga (2002), Solan et al (2001)
 Fischer & Hartnegg (2000), shows that voluntary saccades (the type used for reading)
can be trained in dyslexics by over 10 times their normal rate of maturation so that
they are no longer significantly different from those of non-dyslexics. Training non-
reading saccades (ie. reflex saccades) for the same time period of time however does
not improve voluntary saccades (anti-saccades).

 Furthermore, training eye movements reduces the number of errors observed in
reading (green bars) compared to a control group that received reading intervention
alone (red bars). Training typically took 10 minutes a day over a 3 to 8 week period.
Fischer & Hartnegg (2008)
 Saccade training has also been shown to significantly improve reading fluency for
elementary school students in a randomized crossover trial. Training was done in
school for 20 minutes a day (3 days a week) for 6 weeks. Leong et al (2014)

 Patching one eye while reading can improve fixation by reducing binocular instability
(eye wobble) in younger children resulting in significant improvements in reading
compared to placebo controls or other types of remedial methods.
Stein, Richardson & Fowler (2000)
 A reduction in binocular instability with monocular occlusion has also been reported by
Fischer and Hartnegg (2008) as shown in the graph below.

 Visual counting and subitizing can be trained. Groffman 2008
 This can lead to improvements in basic arithmetic (on DEMAT) as shown in the graph
below, Fischer, Kongeter & Hartnegg (2008).
 Group 1 has 3 weeks of training (green) and then waits but continues to improve
(blue).
 Group 2 waits with no improvement (red) and is then trained showing significant
improvements in basic arithmetic (yellow).

 Studies show that the visual span can be trained with subsequent improvements in
reading speed of around 40 to 60%. Legge et al (2007), Kwon et al (2007), Chung et
al (2004)
 Training the visual span in dyslexia can also result in faster reading speed (confirmed
with fMRI scan). Valdois et al (2013), Geiger et al (1994)

 As reading appears to be dependent upon the development of visual spatial coding it
is not unreasonable to expect that visual spatial training (that draws on similar spatial
coding patterns required for reading) should translate into better reading skills.
 Studies that use sinusoidal gratings (where the student has to respond in which
direction the grating moves), have been shown to improve reading outcomes for
students with dyslexia compared to age matched controls. The treatment was given
twice a week for 15 minutes over a 16 week period. This demonstrates that targeting
the visuospatial system with regular training can help remediate learning problems.
Lawton (2004), Lawton (2007), Lawton (2011)
 Another approach that is used routinely in optometric vision training uses symbol
charts (eg. arrows and pdpq’s) and links them to kinesthetic awareness.
 This method differs from earlier methods of perceptual training described in the
literature (eg. identifying shapes, labelling body parts, matching the start and ends of
words etc) as it uses developmental principles of daily repetition in combination with
progressively increasing the task difficulty.
 This approach appears promising however there is currently a need for more studies.
Mandani (2009), Fredericks (2006), Pienaar (2011)

 Multiple studies show that auditory skills can be trained. Schaffler, Sonntag, Hartnegg,
Fischer (2004), Gaab et al, (2007), Murphy & Schocat (2011).
Schaffler, Sonntag, Hartnegg,
Fischer (2004)

 Studies are mixed when it comes to showing that auditory training can help with
reading (converting graphemes to phonemes). Temple et al (2003), Gaab et al (2007),
Hook (2001), Strong et al (2010)
 Auditory training however may be more helpful for assisting with spelling as shown by
the green bars below compared with the wait group and placebo controls. Schaffler,
Sonntag, Hartnegg, Fischer (2004)

 Research done by Professor Stein and colleagues at Oxford University show that
tinted lenses (blue and yellow) can improve reading in selected students with dyslexia
by around 2 months/month compared to placebos (grey). Normal progress is
considered to be 1 month/month with most dyslexics falling below this. Ray, Fowler,
Stein (2005), Hall, Ray, Harries, Stein (2013),
 Other controlled studies show a positive effect of tinted overlays on reading for
selected students. Noble et al (2004)

 Evidence such as this has led to the Visual Model of reading.
 This is summarized in the book Visual Aspects of Dyslexia by Stein & Kapoula.
 It does not necessarily replace the Phonological Model since BOTH may be true.
 Furthermore, students with learning difficulties still require educational assistance!
 This view is supported by the American Optometry Association who claim that
“unresolved visual deficits can impair the ability to respond fully to educational
instruction. Management may require optical correction, vision therapy, or a
combination of both.”
“Dyslexia affects about 10% of all children and is a potent cause
of loss of self-confidence, personal and family misery, and waste
of potential. Although the dominant view is that it is caused
specifically by linguistic/phonological weakness, recent research
within the field of neuroscience has shown that it is associated
with visual processing problems as well. These discoveries have
led to a resurgence in visual methods of treatment, which have
shown promising results.”

 Independent research from the University of Padua in Italy claims that not only does
developmental dyslexia have a visual perceptual basis but that we should consider
perceptual training for students with dyslexia as well as for young at risk students.
Gori & Facoetti (2013)
“Our aim is to review the literature supporting a possible role of perceptual learning (PL) in
helping to solve the puzzle called DD (Developmental Dyslexia). PL is defined as improvement
of perceptual skills with practice. Based on the previous literature showing how PL is able to
selectively change visual abilities, we here propose to use PL to improve the impaired visual
functions characterizing DD and, in particular, the visual deficits that could be developmentally
related to an early magnocellular-dorsal pathway and selective attention dysfunction. The
crucial visual attention deficits that are causally linked to DD could be, indeed, strongly
reduced by training the magnocellular-dorsal pathway with the PL, and learning to read for
children with DD would not be anymore such a difficult task. This new remediation approach –
not involving any phonological or orthographic training – could be also used to develop new
prevention programs for pre-reading children at DD risk”.

 Visual factors such as refractive error (eg. long-sight or hyperopia over +1.00DS)
and vergence facility (binocular co-ordination) whilst not considered to be a basis for
dyslexia, are significantly related to reading (see graph below) and so should not be
overlooked. Quaid & Simpson (2003)
 All students with a significant learning problem should have a thorough optometric
assessment before starting vision training.

 Havn’t we disproved the perceptual theory or shown that perceptual factors only play a
minor role? Vellutino et al (2004), Ramus (2002)
 There are numerous studies to suggest that vision is not a factor in reading problems
or dyslexia and one can use these to support an argument against the role of vision. In
the end, one must critically examine each of the studies to see if their conclusions hold.
 In the 80’s it was believed that erratic eye movements observed in dyslexia were due to
poor reading skills. The methods used to study eye movements however were not
adequate to draw such conclusions. Using current scientific methods it can be shown
that a problem exists with eye movement control in dyslexia independently of language.
 Another reason for finding a lack of significance can be due to “ceiling effects” (eg.
when the test is not sensitive enough to discriminate between two groups) This was
argued by Fletcher & Satz (1979) when we moved away from the perceptual model.
 A study may also show no significant difference because of the way a group is selected
for testing. Eg. giving all dyslexic students tinted lenses.
 Finally, a study may show no difference because of the manner in which a treatment is
applied. An example might be the Perceptual Motor Programme (PMP) used in many
NZ schools. A study by Klomp (2012) found no effect on learning outcomes for young
primary school children. The study was done in just 10 weeks and targets a gross level
of perceptual motor development. In order to show a significant improvement in
academic learning however would require that the perceptual motor development be
improved to a level necessary to support academic skills.

 The position statement by the American Academy of Ophthalmology (2014) claims
that “children with dyslexia or related learning disabilities have the same visual
function and ocular health as children without such conditions” .
 The evidence clearly shows however that students with dyslexia or related learning
disabilities do NOT have the same visual function as those without such conditions!
Eden (1995), Kulp,Schmidt (1996), Kulp (1999), Maples (2003), Valdois (2004),
Goldstand (2005), Solan (2007), Shin (2009), Bosse (2009), Chen (2011), Franceshini
(2012), Pienaar (2013)
 They also argue that since children with dyslexia like to play computer games (a highly
visual task) that vision cannot be a factor.
 This is not supported by any evidence. The eye movements used for computer games
are NOT the same as those used for reading books. Also, the nature of the visual
tasks found in gaming are quite different from reading text.
 They claim there is inadequate scientific evidence to support visual interventions.
 In fact there is quite a lot of evidence to support visual interventions as shown by this
review but there are not many randomized placebo controlled trials (studies providing
the highest level of evidence). This does not mean that visual interventions are not
“evidence based” however as most medical treatments also fail to meet this standard.
The basis for speech therapy, occupational therapy and rehabilitative medicine is that
the brain is plastic and can be trained. The evidence showing that vision can be
trained is at least as good. If this is accepted in other fields, one must accept the
possibility that vision can also be trained.

 A study by Olulade et al (2013) was widely promoted in the media claiming to rule
out vision as a factor in dyslexia.
 The study showed that visual motion activity measured using fMRI brain scans to be
less in dyslexic students compared with non-dyslexic students of the same age.
 However when dyslexics were compared with younger non-dyslexic students of the
same reading age then the visual activity was about the same.
 Furthermore, when dyslexics are given reading intervention visual activity increased
suggesting that any failure in vision was due to inadequate reading exposure.
 These findings taken together are used to support the Phonological Model.
 This finding argues the point that the visual activity is normal relative to reading age
and that reduced visual activity is therefore a function of low reading exposure.
 Another explanation however is that the reduced reading age of dyslexics is a
function of their poor visual development! The lower the visual activity the lower the
reading age. This being the case we would expect that improving visual development
would improve the reading age by removing visual barriers to reading.
 The fact that reading practice improves visual activity is not too surprising since there
may be a level of “reciprocal effect” in much the same way there is with phonological
processing and reading practice.

 There exists a large body of evidence to show that visual skills are related to reading
ability and that visual problems are linked with dyslexia.
 Much of the evidence points towards a problem with the development of visual skills
supported by the Magnocellular Pathway, however general optometric findings should
also be considered for individual students.
 Although more studies exist to show a phonological link (due to the higher level of
attention it has received) there are limitations to the Phonological Model.
 The evidence that visual skills can be improved with training is substantial.
 More placebo controlled studies showing the efficacy of visual treatments for dyslexia
are needed but this does not negate the many controlled studies and clinical reports
currently available or preclude it as an evidence-based intervention.
 Without intervention the gap in visual skills will often persist despite maturation.
 The view that vision problems do not contribute to the symptoms observed in dyslexia
or general learning disabilities seems very unlikely.
 Given the currently available evidence a more balanced approach may be to use
visual (and auditory) interventions to complement traditional therapies.

Other Presentations:
The Visual Model of Reading
iCept – For Students with Learning Delays
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