Irlen syndrome

Irlen syndrome also referred to as Meares-Irlen syndrome previously known as “scotopic sensitivity syndrome” or visual stress. is a condition characterized by reading difficulties that are mitigated by wearing colored filters of a specific tint ¹. Visual stress is one of the hallmarks of Irlen Syndrome. Visual stress in Irlen Syndrome has been defined as the inability to see comfortably without distortion and discomfort ². It is sensory in origin and is related to characteristics of the visual stimulus. This is in contrast to visual stress caused by visuo-motor deficits such as defects in accommodation or binocular vision. Because of the distinction, current researchers are terming the sensory type of visual stress, Pattern Related Visual Stress ³.

Irlen Syndrome is commonly defined as a perceptual processing disorder, suggesting that the brain is unable to properly process visual information from the eyes because of sensitivity to certain wavelengths of light. Symptoms are said to include poor concentration; difficulties with reading, writing and comprehension; glare sensitivity; headaches and poor depth perception. Meares ⁴ and later Irlen and Lass ⁵ described a syndrome involving visual distortion that can be alleviated with colored filters ⁶. However, Irlen syndrome is not recognized by the medical community or the World Health Organization (WHO) ⁷. This is in accordance with a joint statement issued in 1984, and reaffirmed in 2014, by the American Academy of Ophthalmology, the American Academy of Pediatrics, the American Association for Pediatric Ophthalmology and Strabismus and the American Association of Certified Orthoptists. The Royal Australian and New Zealand College of Ophthalmologists ⁷ has released a position statement explaining that there is no evidence that Irlen Syndrome exists and that there is no proof that supposed treatments, such as Irlen lenses, help those with reading difficulties. “The real concern with diagnoses of Irlen syndrome,” explains the Royal Australian and New Zealand College of Ophthalmologists spokesperson Prof Frank Martin, “is that it can distract from genuine diagnosis and treatment, such as a comprehensive evaluation by an educational psychologist followed by the appropriate remedial educational input. Any interventions that distract from and delay this evaluation could be detrimental to the effective treatment of any learning disabilities” ⁸.

The Royal Australian and New Zealand College of Ophthalmologists’ Irlen syndrome position statement states that “Despite Irlen Syndrome being first described in the early 1980s, there is still no sound theoretical basis or evidence that the condition actually exists ⁷. A diagnosis of Irlen Syndrome is based solely on symptoms with no quantitative physiological correlation” ⁷.

Treatments associated with Irlen syndrome such as colored lenses have not been proven to be any more effective in improving reading difficulties in children than in children assessed in a control group (without colored lenses and associated ‘treatments’) ⁷. The Royal Australian and New Zealand College of Ophthalmologists’ Irlen Syndrome position statement explains that there is no documented evidence to say that Irlen lenses are harmful, but the use of unproven methods may waste time and financial resources preventing a child from receiving the appropriate evidence-based educational remedies that could actually help with their learning development.

“Overwhelmingly the research shows no benefit from this treatment in children with reading difficulties and vulnerable parents are being exploited and having their children subjected to unnecessary screening practices,” said Prof Frank Martin ⁷.

Irlen Syndrome was defined by Helen Irlen in 1983 as not an optical problem, but a perceptual processing disorder, specifically that the brain is unable to properly process visual information transmitted from the eye because of sensitivity to certain wavelengths of light ⁹. This is said to lead to “visual stress” and “distortions” which result in diverse symptoms such as poor concentration, difficulties with reading, writing and comprehension, glare sensitivity, headaches and poor depth perception ¹⁰. Irlen syndrome tends to run in families and is not currently identified by other standardized educational or medical tests. Colored overlays and tinted lenses are purported to improve reading ability and visual perception, increase sustained reading time, and eliminate symptoms associated with reading, such as light sensitivity, eyestrain, headaches, blurring of print, loss of place, and watery eyes ¹¹.

Irlen syndrome can affect many different areas, including ⁹:

• Academic and work performance
• Behavior
• Attention
• Ability to sit still
• Concentration

Irlen Syndrome can manifest itself differently for each individual. Irlen Syndrome is not remediable and is often a lifetime barrier to learning and performance. If you suffer from any of the following, Irlen syndrome might be your problem ⁹:

• Print looks different
• Environment looks different
• Slow or inefficient reading
• Poor comprehension
• Eye strain
• Fatigue
• Headaches
• Difficulty with math computation
• Difficulty copying
• Difficulty reading music
• Poor sports performance
• Poor depth-perception
• Low motivation
• Low self-esteem

However, the symptoms of Irlen syndrome should be differentially diagnosed from other ophthalmologic disorders such as refractive errors, exophoria and posterior subcapsular cataracts, which have similar non-specific visual symptoms to Irlen syndrome ¹².

How common is Irlen syndrome?

Prevalence rates differ widely in the literature and this is, at least partly, due to the criteria which requires individuals (often children) to self-report their symptoms. Irlen reports around 50% of children and adults with reading, learning, or attention problems have Irlen Syndrome ⁹. When combining information from multiple studies, Kriss and Evans ² suggest the point prevalence rate of Meares-Irlen Syndrome is approximately 20% in the general population. This figure is hard to ratify given the various figures touted in the literature. Smith and Wilkins ¹³ report that over 50% of children in mainstream education will report benefit from using filters. As only half of this group will sustain usage (a criterion for diagnosis) they state 25% of school children have Irlen Syndrome though not all will have reading difficulties ¹⁴. Singleton and Trotter ¹⁵ speculate that 12% of the general population have Irlen syndrome and estimate the prevalence amongst those with dyslexia is much higher, perhaps as great as 65%. Other proponents of Irlen syndrome quote that 12-15% of the general population is affected, and 45% of those with learning difficulties ¹⁶.

Irlen syndrome controversy

Lack of scientific evidence that Irlen syndrome exists as an entity

Despite Irlen syndrome being first described in the early 1980’s there is still no sound theoretical basis or evidence that the condition actually exists ⁷. A diagnosis of Irlen syndrome is based solely on symptoms with no quantitative physiological correlation. There remains a lack of clearly established criteria. In fact, the only defining criterion is a self-reported benefit of colored filters while reading ¹⁷. While the premise is “scotopic” sensitivity, it is the photopic system that is used for reading ¹⁸. Importantly, those with Irlen syndrome do not show any electrophysiological changes of retinal function compared to control groups ¹⁹. There is also a large disparity in prevalence rates which suggests a fundamental problem in definition ²⁰.

Lack of evidence that treatment for Irlen syndrome is effective

Consistently, systematic and critical reviews have shown no scientific basis for the benefit of tinted lenses in reading disorders ¹⁷, ²¹, ²², ²³.

There are no objective quantitative measurements available to assess or monitor treatment. The studies that have purported to show some benefit have generally suffered from poor methodology, selection bias, small sample numbers and lack of control groups. Often these are individual reports or testimonials, interviews or anecdotalevidence ¹⁷, ²², ²³.

Issues with lens choice

1. Each individual is required to indicate their preference for colored overlay/lenses. Not surprisingly a gender-based preference is often apparent with girls generally choosing pink or purple tints whereas the boys generally choose blue tints ²⁴.
2. Poor repeatability of color choices – proponents of Irlen syndrome and visual stress claim that a very precise color is needed and highly specific to the individual, which only they are able to provide. Furthermore, they claim that the useof an incorrect color would actually worsen the individual’s symptoms. It would therefore follow that there would be high repeatability in color choice, but recent studies have shown poor inter-test consistency and repeatability ²⁴.

Issues with self-reporting

There are obvious problems inherent in any practice which relies solely on a population to self-report their symptoms and/or respond to leading questions, and this is particularly so in children. Symptoms of Irlen syndrome are vague, non-specific and can be highly variable from day to day depending on external factors such as tiredness or illness. In addition, they frequently overlap with known ocular disorders e.g. convergence insufficiency, accommodation difficulties or refractive errors.

What do you say to parents who claim to see great improvement in their child’s reading with Irlen lenses?

There are several reasons why this may appear to be the case:

1. Placebo effect: Believing the lenses will help may give the impression of improvement. However, studies have shown improvements in reading with colored overlays and lenses are no greater than in control groups ²⁵, ²², ²⁶, ¹⁷.
2. Performance bias (Hawthorne effect): A person who realizes that they are being observed or tested tends to change their behavior to perform at their best.
3. Increased attention: A parent showing more interest and spending more time reading with a child is likely to have a beneficial effect on the child’s level of reading.
4. Concurrent remedial program: Many children are also in reading assistance programs which are likely to improve reading.
5. Natural development: Improvement in reading is a natural consequence of development and maturation. A child’s reading ability is likely to improve with age and practice regardless of whether Irlen lenses are used.

Irlen syndrome causes

Irlen syndrome or Meares-Irlen syndrome is considered a magnocellular system disorder that induces visual stress and distortion, causing reading difficulties by hyper-transmission of a specific light wave ²⁷. The use of color-filtered lenses is useful for improving visual symptoms ²⁸. Colored overlays and tinted lenses are purported to improve reading ability and visual perception and eliminate symptoms associated with reading, such as light sensitivity, eyestrain, headaches, blurring of print, loss of place, and watery eyes ¹¹.

Kim et al ²⁹ believe that the results of the fMRI suggest the possibility of the existence of Irlen syndrome and explain the effectiveness of color-tinted lenses in patients with Irlen syndrome. Further large studies on the activated region in Irlen syndrome are required to provide strong evidence for the existence of a physiological basis of Irlen syndrome and moreover, to provide an explanation for the improvements in reading with colored lenses.

Magnocellular theory

The magnocellular theory stems from an analysis of the visual system. The lateral geniculate nucleus (LGN) is the primary visual processing area for information received via the retina. The layers of the lateral geniculate nucleus are arranged in two major divisions. The upper division, which contains approximately 80% of the cells, is called the parvocellular or sustained system. This system is responsible for mediating colour vision and detecting fine spatial details and is responsible for more detailed visual perception ³⁰. The lower division of the lateral geniculate nucleus, containing approximately 10% of cells, is the magnocellular or transient system, which is responsible for locating objects in the field of vision, executing actions and responding to movement and form ³¹. Recently, a third layer has been discovered, the koniocellular layer which is believed to be responsible for colour vision though even the existence of this layer is questioned by some researchers ³⁰.

These visual fields interact with each other, each system receiving separate information from the retina and transmitting this to the visual cortex. The output from the three systems is subsequently combined in the visual cortex to form one unified perception ³⁰. The transient or magnocellular system provides information as to where objects are in space, whilst the sustained or parvocellular system answers the more basic visual question of “What is this?” ³². The sustained system is reported to receive information from the transient system to prevent image overlap or blurring and thus provide visual stability ³¹. Proponents of the theory of magnocellular deficit as a causal factor in Irlen Syndrome pinpoint magnocellular dysfunction as a possible reason for visual perceptual difficulties ³¹.

Reading as a task involves periods of eye fixation followed by periods of eye movement. In order to be a successful reader, sequential scanning of individual letters is required during each fixation period. As the magnocellular system is responsible for directing focal attention, any abnormalities in this system will therefore compromise the ability to read ³³.

The magnocellular system and dyslexia

Much has been made of links between magnocellular deficits and dyslexia. In fact, some suggest that magnocellular deficits occur in up to 70% of individuals with a diagnosis of dyslexia ³⁴. This, they believe, adds credence to the notion of this visual system being implicated in Irlen syndrome given the high reported prevalence of Irlen syndrome in the dyslexia population.

Deficits in the magnocellular or transient system indicate problems with visual motor processing. This has been noted in dyslexia, where poor eye movement control can be a feature ¹⁵.

Theories that postulate a link between magnocellular system deficits and dyslexia rest on the already established link between magnocelluar deficit and binocular instability. Such instability is theorized to potentially cue visual distortions during reading activities ³⁴. Genetic research has also posited a link, suggesting that defects on chromosome 6 which have been linked to dyslexia are also implicated in the development of the magnocellular system ³³.

Though early functional magnetic resonance imaging studies showed support for the link between dyslexia and transient system deficits ³⁵, recent research raises doubts about the causality of such defects and suggests that because not all individuals with dyslexia have such problems, magnocellular deficits may simply be a correlate of reading problems ³⁶.

The effect of color on the magnocellular system

In magnocellular theory, the use of color is thought to boost magnocellular activity and therefore remediate defects in this visual system ³⁷. Research suggests that cells in the magnocellular system are suppressed in red light; therefore, it would make sense to assume that the color blue used as an overlay would be more effective in reducing the relative contribution of the other, parvocellular pathway, thereby restoring the balance between the two systems ³⁸.

Yellow has also been implicated as a color beneficial to those with magnocellular deficits. Ludlow and colleagues ³⁷ suggest that it is the blue pathway that needs to be inhibited. Yellow is able to do this by boosting red and green cone input to the magnocellular visual system. Both yellow and blue filters and overlays have been found to help children diagnosed with Irlen Syndrome overcome reading difficulties ³⁷.

In a recent study, Smith and Wilkins ¹³ compared a new range of colored overlays called “Reading Rulers” with their Intuitive Coloured Overlay system. The Reading Rulers have a restricted color range that includes blue and yellow overlays to align with the magnocellular theory. The study showed that yellow and blue overlays did not appear to be sufficiently able to benefit all children in the study with regard to reading speed. Other researchers have found that blue overlays have had no effect on rate of reading and red overlays did not compromise performance as would be expected according to magnocellular theory ³⁹.

Whilst these explanations do provide support for the effectiveness of yellow and blue overlays or filters, they do not adequately explain the large individual difference in the choice of and effect of colored overlays which are individually selected from an array of differing hues and intensities ³⁶.

Irlen syndrome symptoms

Common symptoms of Pattern Related Visual Stress reported across the Irlen syndrome literature include ²¹:

• Light sensitivity
• Headache when reading
• Watery eyes
• Excessive blinking
• Fatigue
• Inability to sustain attention
• Poor visual focus

Visual perceptual distortions noted in this population include ²¹:

• Blurring of print
• Movement of print
• Missing lines and individual words
• Losing one’s place when reading
• Difficulty copying and evenly spacing words
• Doubling of text
• Pattern glare from multiple lines per page

Although these characteristics are documented by some researchers, there are other viewpoints that discount the groupings of these characteristics as a specific syndrome and instead view these as idiosyncratic characteristics peculiar to individuals rather than symptomatic of a particular population (e.g. American Optometric Association) ⁴⁰.

Irlen syndrome symptoms as shown on Irlen.com website

Light Sensitivity ⁹:

• Bothered by glare, fluorescent lights, bright lights, sunlight and sometimes lights at night
• Some individuals experience physical symptoms and feel tired, sleepy, dizzy, anxious, or irritable. Others experience headaches, mood changes, restlessness or have difficulty staying focused, especially with bright or fluorescent lights.

Reading problems ⁹:

• Poor comprehension
• Misreads words
• Problems tracking from line to line
• Reads in dim light
• Skips words or lines
• Reads slowly or hesitantly
• Takes breaks
• Loses place
• Avoids reading

Discomfort ⁹:

• Strain and fatigue
• Tired or sleepy
• Headaches or nausea
• Fidgety or restless
• Eyes that hurt or become watery

Attention and concentration problems ⁹:

• Problems with concentration when reading and doing academic tasks
• Often people can appear to have other conditions, such as attention deficit disorder, and are given medication unnecessarily.

Writing problems ⁹:

• Trouble copying
• Unequal spacing
• Unequal letter size
• Writing up or downhill
• Inconsistent spelling

Other characteristics ⁹:

• Strain or fatigue from computer use
• Difficulty reading music
• Sloppy, careless math errors
• Misaligned numbers in columns
• Ineffective use of study time
• Lack of motivation
• Grades do not reflect the amount of effort

Depth perception ⁹:

• Clumsiness
• Difficulty catching balls
• Difficulty judging distances
• Additional caution necessary while driving

Distortions ⁹:

• Words on the page lack clarity or stability; i.e., may appear to be blurry, moving, or disappear

Irlen syndrome diagnosis

It is generally accepted that the presence of Irlen syndrome is confirmed through either one of the two following criterion ³⁶:

• The sustained use of a coloured overlay or filters; or,
• An improvement in the rate of reading by more than 5% when using colored overlay or filters.

Hence, although symptomology is assessed, it is treatment response that dictates diagnosis.

A number of different protocols have been developed to diagnose Irlen syndrome many of which include substantial self-report. Caution has been advised when ascertaining the veracity of child self report on Irlen syndrome screening questionnaires leading to identification of false negatives ². There is some concern that children may not recognise symptoms of Irlen syndrome because of a process of normalization. Others may exaggerate or “fake good” to gain approval. Because of this, some clinicians have suggested that the response to colored overlays is the real diagnostic test for Irlen syndrome ². However, response to overlays is also determined by the self-report of the child. It could also be argued that self report regarding the effectiveness of overlays may lead to false positives through both habituation (to the testing materials) and the Hawthorne effect, given the students know they are undergoing an assessment.

Assessment tools and procedures in common usage in the literature are:

1. Irlen Reading Perceptual Scale®
2. Intuitive Colored Overlays®
3. Assessments of Visual Stress
4. Wilkins Rate of Reading Test

Irlen Reading Perceptual Scale

This original Irlen syndrome protocol was developed by the Irlen Institute that trains and certifies Irlen Screeners and Irlen Diagnosticians who are then able to practice with the endorsement of the Irlen Institute. The assessment instrument used is called the Irlen Reading Perceptual Scale® which consists of four parts including:

• questionnaires to ascertain reading efficiency, strain and fatigue;
• tasks that are considered to immediately create conditions of visual stress and fatigue;
• use of overlays to determine whether reading improves with the application of color;
• and finally, a series of distortion pages to ascertain individual visual perceptual distortions ⁴¹.

Intuitive Colored Overlays

Intuitive Colored Overlays® have been developed by Arnold Wilkins at the Visual Perception Unit at the University of Essex. According to Kriss and Evans ² these are the “gold standard” instruments used to determine a diagnosis of Irlen Syndrome.

The Intuitive Colored Overlays® are a set of nine coloured acetate overlays plus one grey overlay. By using the overlays singularly or in combination, a total of 27 colors can be sampled which represent the chromaticities found in the CIE 1976 UCS diagram. This means that the saturation level is similar for all colours. Pairing colors of neighbouring chromaticity enables sampling of higher levels of saturation ¹³.

A protocol has been developed for use of the overlays that involves presentation of two identical passages of randomly ordered words to an individual suspected of having Irlen syndrome. These two pieces of text are placed side by side and the overlays are then systematically placed over the text and the reader asked a standard set of questions regarding symptoms of visual stress and visual perceptual distortions. The reader then chooses which overlay (or no overlay) improves the reading experience. By a process of elimination, a favored color (from the 9 + 1) is selected for the individual. If an overlay is chosen but does not remove all symptoms, more saturated colors are obtained through adding combinatory overlays ¹³.

A competitor has recently entered the market for provision of overlays with the development of the “Reading Rulers”. According to the Wilkins team, the limited color range in the Reading Rulers (five only) limits their utility ¹³. Other than this study by the Wilkins group, no other literature has been found relating to the efficacy of the Reading Rulers.

Assessments of Visual Stress

Although most assessment of Irlen Syndrome is conducted by a process of measuring the subjective response to presentation of different colored overlays, there are those who advocate for a more objective measure to be used ³.

Because of the universal acceptability of visual stress as a measurable component of Irlen syndrome, some researchers have advocated for the use of a specific assessment of visual stress as part of a battery of measures to inform diagnosis of Irlen syndrome ³. Allen and colleagues ³, suggest that both state and trait measures should be investigated and verified before diagnosis is made. Their assessment protocol includes questionnaires and interviews regarding symptom presence and significance as a trait measure and propose the use of a specific visual test such as reaction to square wave gratings to directly assess the presence of pattern related visual stress. Singleton and Henderson ³⁶ have also tried this approach, using a computerized visual stress screener. However, to date this search for objective validation does not appear to have gained great momentum by others in the field.

Wilkins Rate of Reading Test

Given the agreed upon diagnostic criteria for Irlen Syndrome includes the sustained use of overlays or a subsequent improvement in reading, the secondary part of assessment usually includes gauging performance on a test of reading.

Because most reading tests are designed to measure linguistic function or comprehension, they are not necessarily suited for Irlen screening purposes ⁴². Such tests are reported to often be printed in large text, which can mask any visual perceptual difficulties. The Wilkins group have developed a reading test designed specifically for use in screening for Irlen syndrome called the Wilkins Rate of Reading Test ³⁸. The Wilkins Rate of Reading Test was specifically designed to challenge readers with visual difficulties. The text is small and there is minimal spacing between words. The words themselves are chosen for their linguistic ease and strung together in a meaningless manner, meaning comprehension is not required nor assessed ⁴³.

When reading from standard texts, researchers have noted that there is a time delay before the benefit of overlays is demonstrated. This is thought to be due to deterioration in performance when fatigue sets in as visual stress begins to manifest ³⁸. The alleged benefit of the Wilkins Rate of Reading Test is the discovery that this test can show the benefit of overlays in as little as one minute because the test mimics visually stressful conditions ⁴³.

Irlen syndrome treatment

The standard treatment for Irlen Syndrome is utilization of an individually prescribed colored overlay or lenses (commonly referred to as Irlen filters®). Part of the diagnostic protocol includes the proviso that the condition must be alleviated by application of color through individually prescribed overlays, lenses or filters. The benefits are stated to be both specific and idiosyncratic to the individual ².

Although originally, colored overlays were the only form of treatment available, a further refinement of the process has reportedly occurred with the development (also by Wilkins) of the Intuitive Colorimeter®. The Intuitive Colorimeter® is a piece of equipment similar to that used by optometrists in standard visual examinations but instead of looking through prescription lenses, the Intuitive Colorimeter® allows the perceptual effects of color to be ascertained while the eyes are concurrently adapted to color ⁴⁴. From the results of the assessment with the Intuitive Colorimeter®, tints are able to be prescribed in the form of lenses (used interchangeably with the term “filters’ in the literature). The color that is prescribed through use of the Intuitive Colored Overlays is reportedly never the same as the color prescribed as filters because of the differing wavelength of light involved ⁴⁵.

The Irlen Institute ⁴⁶ also note that the use of overlays is only an intermediate step in
the treatment of Irlen syndrome. They advocate for the use of Irlen Filters® (glasses with colored tints) as they believe that the use of such filters enables greater benefit because of their portability, flexibility and utility. They note that with filters, the color is not perceived when looking through the glasses and also highlight the fact that filters are not the same color as overlays due to the differing light wavelengths involved. In order to receive Irlen Filters®, clients are required to undertake a diagnostic procedure with an Irlen certified diagnostician. As the Irlen Institute holds proprietary ownership of the Irlen protocols, there does not appear to be a large volume of independently published literature documenting clinical trials of the procedures ⁴¹.

The mechanism of treatment success appears to be the premise that the application of color decreases visual stress and increases visual comfort, thus supporting extended periods of reading and enabling decoding techniques and other reading strategies to be applied. It is important to realise that whilst reduction of visual stress appears to affect visual processing ease, it does not teach reading skills ⁴⁷.

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