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                                                                VISUAL DYSLEXIA






For teachers













Ian Jordan



Ian Jordan is a qualified optician with a particular interest in visual processing problems. Although a Geordie by birth (Jarrow) he conducted most of his research in the North East of Scotland where he had a number of optometric practices.

He lectures internationally to all types of audiences and writes extensively. He has developed new optometric diagnostic techniques and has received a number of awards.

He is at present working on some research projects. 






























Visual dyslexia is the name for a group of visual processing problems that make it difficult or impossible for a person to achieve their maximum potential in reading. They are often found in conjunction with other processing difficulties. They may be the primary cause of the problem or as part of a complex processing syndrome. In all cases they must be addressed, as it is impossible to read to the predicted ability of the person if the brain has a corrupted or poor input to work with.

Visual dyslexia is variable in both onset and severity, the earlier it becomes apparent the more severe.

When assessing whether visual dyslexia is present, account must be taken of intellectual ability, as the more intelligent will be able to disguise the problem to a greater extent than the less able. The expectation of the intellectually bright is however higher and the expectation of success greater, consequently they are often the easiest to spot with difficulties. They are often from a family that is able to question both the child and the system; they tend to be the children that get some form of treatment. The child from the family that is less articulate and able to use the system is often given a lesser chance. It is the moral and legal responsibility of the school to ensure that all children are given a reasonable level of care in this area.


It may prove very costly in the future to ignore problems as litigation is inevitably going to increase, and the financial penalties can be extremely high. The mental stress to the teacher will also be high if the child chooses litigation. Not to recognise visual dyslexia may blight a child's life. They will underachieve financially, socially and their self esteem will be damaged. The resultant underachievement and effect on the psyche of the child can be catastrophic. Visual dyslexia must be addressed and treated.




Visual dyslexia responds well to treatment


In virtually all cases visual dyslexia is treatable if not curable. The assessments and treatments vary wildly, some are simple and inexpensive, and others can be extremely costly. The cost of a treatment does not necessarily relate to the chance of success. It therefore follows that knowledge of assessment methods and treatments is essential for parents and teachers to ensure the most satisfactory results.


A language or a visual problem?


The present methods employed to alleviate reading difficulties often neglect the visual problems in favour of language based assessments and treatment. To ignore the physical problems that a child may suffer is not acceptable as all possible educational strategies will have a significant chance of being flawed. Do not accept the status quo; it is both unjustified and unsustainable. To pretend a problem is not there does not mean it goes away, it just means that it is ignored and is untreated. The statement that says dyslexia is purely a language problem is wrong and there is sufficient research published to prove it.

It is essential to correct any physical processing problem before undertaking the use of language based assessments or therapies. This includes visual, auditory and proprioceptive difficulties. 

There is an additional need for language-based therapies to complement physical treatment. This is particularly important if the physical assessments have been delayed. Early intervention is essential for both the visual and auditory therapies as delay reduces effect. Children should not be expected to persevere with these problems; time is not on their side. There are exceptions to this rule and it may be acceptable to wait after due consideration by suitably trained professionals to await physical or neurological development in the child. This diagnosis must be made with care, as a mistake will inevitably reduce the attainments of the child and the consequences may be irreversible. Remember that dyslexia of any type is not a school problem; it affects a child for life.  

How do I recognize the symptoms of visual dyslexia?


Visual dyslexia is one of a spectrum of visual processing conditions that are discreet yet inter-related in their symptoms and treatment. They often interact with other processing conditions such as Dyspraxia, ADD, ADHD and Autism. Differential diagnosis is difficult and it is common for visual processing problems to be present in children suspected with these conditions. It is a good idea to consider whether visual processing problems are present if any other processing problems are experienced and it is advisable to have a visual processing assessment even if it is to rule it out as a factor in the overall condition. It is likely that most of the children with significant problems with processing have a visual component in the problem. A simple eye examination is not sufficient to enable diagnosis.


Although visual dyslexia is often present in pre-school children it is rare for a parent to recognise the symptoms in these children. However some squinting or lazy eyes may indicate a processing problem and a child with these problems must be suspect. It is likely that the normal visual development is disrupted with the result that the visual system does not mature normally.


Early years at school


The first indications of visual dyslexia are often noticed when the child attends school. The visual apparatus of a child is often not developed to an extent that it can cope with the processes required when reading is first encountered.

There is an argument for starting reading later for some children than at present such as in some other countries. Early reading when the visual system is not ready may be counterproductive.

Symptoms encountered initially are:

Fixation problems

            Tracking problems

            Reversals of words or letters

            Inversions of words or letters

            Double vision

            Letter or word displacement

            Words or letter vibration

            Word or letter movement

            Changes in size or shape of individual letters

            Suppression of background

            Trigeminal nerve effects

            Spatial problems

            Visual plane variations

            Memory access problems

            Memory displacement

            Central visual field changes

            Peripheral field changes

            Proprioceptive problems

            Auditory processing difficulties


            Mid line crossing difficulties

            Fusional difficulties




Fixation problems are common and are characterised by the child having to look away from the page, poor concentration and inability to maintain focus on a word. Their eyes often appear to "bounce" around the page.

Fixation develops with age; at five many will find it difficult to maintain gaze on a word, at eight most should be capable - but many are not. Convergence insufficiency i.e. the reduction in the ability of the eyes to rotate to a point stimulus is usually found and a reduction in the ability to accommodate is often present. The child will often close one eye when reading or when tired. Teachers should be aware that the child may disguise this act by laying their head on the desk and covering one eye with their arm. They may rotate or move the book to a position in which it is easier to suppress one eye, this symptom should ring alarm bells. The child will often take up an unusual reading position. The child may not want to read.

The treatments for fixation difficulties depend on the cause. The normal optometric treatment (assuming there is no prescription problem) is to use convergence exercises (success is idiosyncratic and regresses when stopped).

If the convergence problem is a consequence of suppressional or fusional problems then it is more appropriate to treat these.

 The visual tracking magnifier and filters will often be of great benefit.





Tracking is the act of moving along the line and from one line to another. If a child has tracking problems then there is always a visual difficulty.

There are many reasons for tracking problems and the treatment will reflect the cause of the problem.

Many children they will have difficulty in Saccadal eye movement. This is the type of eye movement in which the eye fixates on one word, moves along the line and fixates on another word. Small corrective movements and reverse eye movements are found and these may be disrupted in some with processing problems.

Rate of reading tests may be used in this case with some success. Treatments include colour filters, overlays, occlusion, retinal rivalry modification and exercises.   

A further cause of tracking problems is visual plane disturbance. This is where the appearance of the text is distorted in such a way as to make the lines of print appear to not to be parallel. This is relatively common and may be due to refractive error, spectacles and retinal fusional problems (monocular or binocular). There are a number of treatments that may be utilized, colour filters, the visual tracking magnifier, blockdown, yoke prisms, modification of spectacle prescription and modification of lens design.

Factors that influence tracking difficulties in the classroom include the print presentation on a page, the distance of the book from the child, the lighting in the classroom and the physical dimensions of the paragraph. Proprioceptive problems are often present and may be significant in dyspraxia.


The child's eyes may have some difficulties in crossing the mid line and double vision is common. This may be intermittent and due to angular changes on movement away from central fixation. This symptom is treatable with the visual tracking magnifier, colour and exercises. Changes in text presentation may be beneficial.


Perceptual effects that distort words or letters; or lines changing shape, position or orientation may also produce difficulties that make tracking difficult. These will be dealt with in more detail later.








A common early problem is that of visual reversal or inversions of letters or words. A child often sees words or letters the wrong way round!

This common and yet frequently ignored symptom must be differentiated from the sequential memory effect in which some children see the words correctly but reverse them within the memory system.

Turning the letters or words upside down should be considered visual in virtually all cases.


Visual reversals


The most common form of visual reversals are d/b p/q and was/saw. This type of reversal can be stopped in virtually all cases using visual treatments. The optimeyes will often allow the child to see the letters or words flip back and forward whilst viewing!! The visual tracking magnifier will usually stop visual reversals immediately.  

Visual inversions are less common but much more dramatic. The simplest form of inversion is d/q or t/f  but in more extreme cases whole words, lines or areas of text can totally invert. Inversions can be treated very successfully by a knowledgeable practitioner.


In both reversals and inversions the symptoms may be found in one eye only with resultant symptoms depending on the dominance of the eye and the target presented.


In visual reversals or inversions the size of the target is critical, magnification or minification may stop the effect immediately. Therefore the way text is presented can be a contributory factor in this difficulty. The type of text, the font, the position, the thickness of the lines may influence the effect.

Colour treatment may be employed in the treatment of these conditions. However a significant level of knowledge is required and it is sensible to understand the limitations of the assessor.

 Lack of knowledge often can create problems or stop appropriate treatment being undertaken.  


The best way of achieving optimum colour is the optimeyes task light. This light is designed to switch on and off individual colour receptors in the retina thereby allowing the most appropriate balance to be achieved. It will virtually always be more accurate than spectacle lenses or overlays.

Narrow spectrum filter spectacle lenses would be the next best treatment but these are difficult to obtain and can be extremely expensive. In practice they can only be used experimentally and are not commercially available. Broad spectrum filters are the usual commercial type of tinted lens used to treat dyslexia and great claims are often made as to the accuracy in giving the perfect colour. The fact is - the claims made are questionable and I would say they are at times ludicrous. They are inevitably limited in efficacy due to the limitations of dyes and lens materials. There are new narrower filters becoming available soon. I have found these to be more satisfactory experimentally but they still have some limitations. A panacea is not possible.

Overlays may appear to be useful in education but a teacher must be aware of the potential problems associated with overlays. They should only be used as a temporary aid or under professional supervision. It can be harmful and potentially risky in terms of future litigation if a teacher takes it upon themselves to use overlays in other ways.

If overlays are helpful it is essential that further investigation is undertaken, if they are not useful it still may be that colour therapies should be fully assessed.

A significant level of knowledge is required of the lighting, the visual responses to colour and the effects of three dimensional colour space and metamerism. If you do not know and understand these terms you should not use overlays without advice except as a temporary solution until the child has been fully assessed!

It is unlikely that anyone other than an optician with a high level of interest would have anything like enough knowledge. This area of optics may appear straightforward; in fact it is extraordinarily complex.

A little knowledge is not sufficient for proficiency.

However, I believe it to be essential that a child with problems that may be alleviated by the use of colour has the opportunity to experience the effect of the optimeyes task light at school. It is vital that all teachers should access and know how to use it.  Dramatic improvements are often possible. There is no equivalent technique.



Memory reversals


When a person sees a word correctly but remembers it the order of the letters incorrectly it may be called a memory reversal. In this type of reversal it is appropriate to try to improve the memory recall by the use of memory exercises either manually or by use of a computer programmes. Improvements are possible but may require significant input by the child or parent.

Memory both visual and auditory should be assessed. The norms for forward digit span increase by one digit per year (plus or minus two digits) up to seven years. Reverse span is usually one less. Other memory tests would also be beneficial.

If digit span is less than five, phonics will be difficult.




Blurring of text may be noticed. This may be due to a visual problem e.g. refractive errors, spasm, fatigue or over-stimulus. Alternatively a visual processing difficulty may be implicated. Professional advice is necessary to determine both the cause and

most appropriate treatment.

Blurring is often accompanied by double vision and may in some cases be mistaken for double vision in which the separation of the images is small.


Double vision


Double vision (diplopia) is extremely common in visual processing problems. It may be present in a number of forms.

The most common is that of suppressional problems of the double image created during convergence. This effect may lead to a reduction in the ability of the eyes to converge and can be treated by the use of exercises, colour or prisms. There is much discussion in the optical world on the most appropriate treatment. I have become convinced that colour is usually the best method of treatment if fusional/ suppressional problems are indicated although others may disagree.

Double vision may only be present at on side of eye movement i.e. at one side of the page.

Restriction of eye movement may be present due to this problem and tracking problems may be present. Ball sports may be a problem. It may also be of significant importance in dyspraxia as proper proprioceptive development may be flawed.


There are more awkward types of double vision. These are found in many with dyslexia,

In some children reversals of letters may be concurrent with the correct interpretation e.g. a child may see both the d and b combined to create a letter that has a long central line bisecting the circle at the base.

Some words may split horizontally or vertically with the background remaining stable. It is often found in one eye only and may be stopped with changing the retinal colour balance.

In some cases the letter size and type determines the double vision. This may be either a monocular or binocular effect. An annulus of multiple images may seen or a second image may break and move a significant distance from the fixated image, correlating well with the word or letter displacement found in so many dyslexic children.  




Letter or word displacement


Word or letter displacement may take a number of forms. Letter displacement may involve the letter sequence being changed within a word e.g. was / saw or the letters appearing to be in an adjacent word or line. Words may appear in different places within the text and in the most extreme cases whole lines appear to be in the wrong position. In rare cases the orientation may be changed e.g. the words may appear at an angle or upside down.

Displacement of words or letters is often seen by dyslexic children and is usually misdiagnosed as a memory problem. If a child sees words or letters in the wrong place it is always a visual problem and is very treatable. The symptoms can be alleviated in a number of ways, colour, blockdown and magnification/ minification. These may have to be combined for optimum results. It is absolutely essential that these symptoms are alleviated in any child with reading problems as soon as possible.  


Words or letter vibration


A common symptom in visual dyslexia is letter or word vibration. The most common type is whole word vibration although single letters may show this anomaly. The vibration speed, direction and amplitude vary. Magnification, colour and blockdown will stop this effect.


Word or letter movement


Perhaps the most common problem in visual dyslexia is letter or word instability on the page. To create this effect it is usually necessary to have an area in which high contrast figures such as stripes or text are closely packed. The area becomes unstable and often appears to move spontaneously. It can create problems in many areas other than reading such ironing striped shirts, and with escalators and open staircases. It can be made worse by increasing the amount of light, making the contrast greater or introducing flicker.

This instability is often the cause of night driving problems, migraine, agoraphobia, attention problems and in most extreme cases epileptic seizures.

Treatment is possible using colour, magnification, minification and blockdown.


Changes in size or shape of individual letters


In rare cases the ambient lighting may give rise to anomalous figures that can be corrected by modifying the lighting or by use of colour.


Suppression of background


As the eyes converge it is necessary to ignore or double vision caused by the misalignment of the peripheral retinas. This suppression may be learnt through exercises (with variable results) or it may be possible to suppress immediately by the use of colour. Occasionally the brain may choose to suppress the central image in one eye or differently depending on the task. Suppressional problems will result in

            Double vision

            Closing one eye whilst reading

            Tracking problems

            Possible dyspraxia

            Abnormal reading position


Trigeminal nerve effects


Trigeminal effects of visual processing problems can be dramatic. The most common symptom is frontal headache or discomfort that is often misdiagnosed as sinusitis. Migraine can be a more extreme version of this type of headache and is very successfully treated using visual techniques in a high proportion of cases.

Hot sandy eyes dry eyes respond well to treatment if inappropriate visual stimulus is the cause of the problem. Hearing can be helped using visual techniques and both the tonal quality and volume can be modified. The ability to filter out background noise is enhanced in significant numbers of people.


Inappropriate lighting (lighting is particularly bad in many schools) and presentation of text may predispose a child to these problems. A child will usually rub their eyes and may complain of discomfort. They often suffer from frontal headaches, migraines, hearing problems and stomach aches.


Spatial problems


Spatial awareness problems are common and may be due to a number of causes. Areas in the eyes that should be coincident may be displaced or distorted. This inevitably leads to problems with proprioceptive development and may result in symptoms. The most common symptoms that may be found at school are


            Inability to catch a ball

            Turning the book or page to an angle when reading

            Closing one eye when reading


            Double vision

            Postural changes e.g. head tilt


Treatment depends on the cause and may include spectacles or contact lenses (or a combination of both), exercises, prisms, colour and modification of the visual field.


Visual plane variations


In many children their visual planes are distorted. This means that if a child looks at a book it will appear as though it is tilted, horizontally, vertically or both. The angle of tilt can be significant (40 degrees plus). The floor and other vertical or horizontal objects appear to slope. This slope changes with the angle of gaze.

A high proportion of dyspraxic children will suffer from this problem and as a consequence will find their ability to develop spatial awareness difficult. Children may describe the words "falling off the page". The words may also compress at one end leading to inability to see the end of the word or the letters may overlap. The child may guess the ends of the words.

Treatment would normally aim to restore the visual plane to normal. This may be done by optical or colour methods.









Central vision (Parvocellular)


When looking at a word it is necessary to be able to discriminate small changes in shape and size for accurate decoding of the word. This enables whole word or phonic deciphering to be applied. However, a high proportion of those with reading or other processing problems are not able to see some words accurately. This means that it is essential that this problem is ruled out as soon as possible in a child with reading difficulties as all teaching methods will be flawed or reduced in efficacy.

There are a number of different types of central visual problems and they require expert analysis. The perceptual problems that are most common are

            Changes in letter shape or orientation

            Central visual field loss

            Multiple images

            Change of colour

            Reversal of black to white and vice versa


The most common symptoms are seeing words in different areas of the page, parts of words disappearing (a common effect), central area disappearance or movement (may be dependant on gaze), amblyopia (lazy eye).



Peripheral vision (magnocellular)


The peripheral visual system responds optimally to flicker and edges or stripes. In many with visual processing problems it may be a significant factor in causing symptoms.

Flicker is often implicated in migraine, epilepsy, agoraphobia, asthenopia (frontal headaches and discomfort around the temple area), dry eyes, hearing problems, sick-building syndrome and computer problems. Flickering lights e.g fluorescent lights often cause significant problems.

Light flicker is usually a problem to the visual system in frequencies below 35Hz but some susceptible individuals may be sensitive to 120Hz. The greater the modulation i.e. the difference between the on cycle and the off cycle in the light source, the more the effect. The colour emission of the light source will also have an effect (sometimes disastrously).

Flicker can also be increased by the use of computer screens or televisions. Eye movement over striped surfaces or print may also produce flickering effects.

Movement in the peripheral visual field e.g. during driving may also cause similar effects.

The same type of effect is also caused by pattern. The effect is determined by the contrast between the pattern (or print), the size of the pattern or font, the area covered by the pattern or print, the amount of convergence, the colour of the font and background.

The effects of flicker are cumulative and produce very unpleasant symptoms.


The whole rational of classroom and office design should be considered and the health and safety implications considered.

Symptoms found in the classroom of flicker related problems are


            Eye rubbing

            Difficulty with concentration

            Watery eyes

            Unstable print

            Abnormal pupil size

            Balance problems

            Difficulties with hearing or filtering out background information

Treatments reduce the input stimulus by changing the flicker, the colour, the pattern spaces, the convergence (occlusion / partial occlusion using contact lenses/ prisms)

The peripheral vision can also shut down during suppression or during reading. The effect of is to make the background appear to become black. In some cases it can also happen looking at a television. This can be debilitating and can be treated using colour.


Mid line crossing difficulties


Children with reading difficulties often experience problems that differ depending on the position of gaze. The mid line plays an important role in determining the ability of the child to track along the line. Expert advice is necessary.


Fusional difficulties


Fusional problems are often present in children with processing difficulties. These include squint, muscle balance problems, lazy eye. Treatment of the visual processing difficulty can have significant effects and may alleviate the problem in some cases.








The eyes converge when they rotate so that they both look at a near point or word. In those with reading difficulties it is common to find that the eyes cannot converge to a point close enough to read. This means that a child cannot hold fixation, cannot concentrate, gets double vision, is uncomfortable and will inevitably find reading difficult. In some children this fixation problem only occurs at one side of the mid line and it may be masked by head turning or covering one eye when reading. Sometimes the child will hold a book very close and suppress one eye. Other symptoms found in the classroom include

            Eye rubbing

            Abnormal reading position

            Fixation problems

Treatment is often very successful. The treatments include colour, prisms and exercises. 




Accommodation is the ability of the eyes to change their focus to a close point. There is a predictable drop in accommodative ability throughout life and age can be predicted from it. This does not apply with those with reading difficulties and their age measured this way often is significantly different to that predicted. Colour can restore the accommodation to that predicted from the age of the child. Small refractive corrections may also restore accommodation to a significantly greater effect than expected. Reading additions may also be prescribed to mask the symptoms.   


Auditory processing difficulties


Visual processing problems are linked with auditory processing problems. In some children their vision can be enhanced by sorting out auditory difficulties. Speech difficulties often indicate that sensory integration problems may be present. It is prudent to assume that all children with a visual processing problem have an auditory processing problem and vice versa until shown otherwise. Children with autism are particularly sensitive to auditory and visual processing difficulties and should be routinely assessed.


Memory access problems


When a child reads there are a number of potential areas in which the processing may be a problem. The child may use only the visual system and produce pictures in his mind, instead of making the words into sounds. Comprehension can be a problem as the picture that the child has in the imagination will be used to answer any questions. The child may not use the sight lexicon for recognition of whole words and only read by decoding phonetically every word. There are numerous strategies for teacher in this area to enable a child to make the most of his memory.




Although Synesthesia is often described as a rare condition it is in fact commonly found in those with reading problems. It can be described as a wiring problem in which sensory inputs are confused in the brain. This means that some children see numbers or words as colours, smells as colours, people as flowers or food (I am a chocolate cake!) etc.













Assessment tools for teachers




The best method for screening in the classroom is observation. If a child is below the standard expected a close watch by the class teacher is essential. Visual processing problems should be one of the options considered. It is a good idea to conduct a screening test for visual problems such as the Basic Screening Test by the author, published by desktop publications.


More advanced tests


There are a number of more advanced tests available for the teacher. Training is essential if a teacher wants to perform a more in depth assessment.

A minimum of one day formal training should be undertaken by a specialist teacher with those with a special interest in assessment and recognition taking at least three days. A psychological assessment or eye test does NOT perform the tests required to an adequate level for diagnosis and treatment strategies to be prescribed. Costs can be high BUT the costs of not performing the correct tests can be far higher, both in educational terms, potential damages from litigation and in the impoverishment of the future life of the child. Prison populations have far too many that society has failed with an estimated 70% of inmates dyslexic.


A good way of formalizing the test is to use the interactive cd rom "Visual Dyslexia assessment module" as this asks the relevant questions and prints out a referral letter. It is essential that a clear referral letter is sent and records are properly kept. If you do not write it down - it hasn't been done!

The tests a teacher should ideally undertake in a formal assessment

            A pattern glare test such as the pattern glare screening test is of value in determining the degree of disturbance due to the printed word in the peripheral vision.


A central vision test such as the reversal and inversion test is invaluable for assessing central vision anomalies that cause so much distress in reading.


            An occlusion test i.e. covering one eye and comparing reading monocularly or binocularly. If reading is better with one eye than both there is some sort of visual or visual processing problem.


The optimeyes is essential for assessment and in some cases treatment of children with reading difficulties. There can be no excuse for not assessing a child on this specialised light if necessary.

            The visual tracking magnifier test involves stabilizing print, fixation, reversals and inversions and pattern glare symptoms. It is useful early readers and children with profound visual dyslexia. Every primary class teacher should have one of these inexpensive implements for testing and also to help some children.  


All teachers should have basic knowledge of visual dyslexia; it must become part of their initial training. If ten percent of children do not process adequately visually it is essential that they can deal with these children.














Visual dyslexia is an extremely complex condition that is common and it is essential that teachers are trained and have the tools to deal with it.

Parents should now ask their school "how do you assess visual dyslexia?"

To pretend it does not exist is futile. It does exist and schools have a responsibility of care to ensure that their children are given adequate assessment and treatment. Visual dyslexia is a hidden handicap.

Teaching techniques often provoke symptoms albeit inadvertently, teachers have to be trained to take appropriate action.

Children have an absolute right that society acts to prevent them having a miserable education, underachievement and loss of prospects. Teachers can only act if the political will allows them to, the costs of stopping this problem have to be borne by society. The optical and psychological professions must be obliged to train in this area to enable all children to have access to the most appropriate treatments. Visual dyslexia is not the same as language based dyslexia, language based strategies are inappropriate unless there is a language problem too. Early intervention is essential; children should not have to wait for years to be seen. As soon as the problem is suspected in a child there should be proper assessment and intervention.

Visual dyslexia is an unnecessary luxury; we cannot afford it to continue.