Visual Perceptual Distortions Research Articles

Het Alice in Wonderland-syndroom en psychotische ervaringen: een differentiaaldiagnostische uitdaging

Alice in Wonderland syndrome and psychotic experiences: a challenging differential diagnosis Alice in Wonderland syndrome (AIWS) is an understudied condition associated with a variety of symptoms, from visual and somesthetic perceptual distortions to disturbances in time perception and symptoms in the psychotic spectrum. The syndrome is pathophysiologically associated with cortical dysfunction in sensory brain areas. When AIWS symptoms occur, possible underlying neurological conditions should be investigated as they may be amenable to treatment. From a psychiatric perspective, distinguishing it from disorders within the psychotic spectrum poses a challenge. This article aims to clearly describe the phenomenology and definition of AIWS and to explore whether a strict differential diagnosis with psychotic experiences is possible. To the best of the authors’ knowledge, psychiatric disorders have to this date only been associated with AIWS in adults. A case of a 14-year-old girl with depression and subclinical psychotic symptoms with an unclear origin of AIWS is presented. Presumably, there was a looping effect and the subclinical psychotic symptoms were mistakenly identified as AIWS symptoms. Due to substantial differences in prognosis and treatment, the authors want to emphasize the importance of differentiating AIWS from a (subclinical) psychotic syndrome. It is crucial to thoroughly examine each individual AIWS symptom phenomenologically in all its facets. Additionally, clinicians should be aware of the influence of the looping effect.

Reading skills in children with Irlen Syndrome

Visual perceptual distortions and physical discomfort that cause difficulties in reading are some of the characteristics of Irlen syndrome. This study examined if students with Irlen syndrome, assessed with different reading tasks, present differences in reading skills when compared to those without the condition. Participants were 110 fourth and fifth graders (mean age = 8.6 years), 55 with Irlen syndrome (ISG group) and 55 without the syndrome (control group). Researchers applied the Irlen Reading Perceptual Scale to evaluate the Irlen Syndrome and the PROLEC-R Test to assess reading processes. The results showed significant group differences in Word Reading, Pseudoword Reading, Punctuation Marks, Sentence, and Text Comprehension. Oral comprehension in the auditory modality was not significantly different, which would support the idea that Irlen syndrome seems to be related to visual sensory processes. In conclusion, participants with Irlen syndrome presented impaired reading processes that might affect overall visual comprehension but not oral reading comprehension.

Modality-Independent Effect of Gravity in Shaping the Internal Representation of 3D Space for Visual and Haptic Object Perception.

Visual and haptic perceptions of 3D shape are plagued by distortions, which are influenced by nonvisual factors, such as gravitational vestibular signals. Whether gravity acts directly on the visual or haptic systems or at a higher, modality-independent level of information processing remains unknown. To test these hypotheses, we examined visual and haptic 3D shape perception by asking male and female human subjects to perform a "squaring" task in upright and supine postures and in microgravity. Subjects adjusted one edge of a 3D object to match the length of another in each of the three canonical reference planes, and we recorded the matching errors to obtain a characterization of the perceived 3D shape. The results show opposing, body-centered patterns of errors for visual and haptic modalities, whose amplitudes are negatively correlated, suggesting that they arise in distinct, modality-specific representations that are nevertheless linked at some level. On the other hand, weightlessness significantly modulated both visual and haptic perceptual distortions in the same way, indicating a common, modality-independent origin for gravity's effects. Overall, our findings show a link between modality-specific visual and haptic perceptual distortions and demonstrate a role of gravity-related signals on a modality-independent internal representation of the body and peripersonal 3D space used to interpret incoming sensory inputs.

Poster Session: Visual System Assessment for Predicting a Transition to Psychosis.

Visual system assessments are seldom regarded as a viable way to predict a future psychotic disorder. Here, we argue that may be a missed opportunity. From a large literature, we identify a set of visual tests that have distinguished individuals prior to or near the first psychotic episode or that have shown group differences independently of illness duration. Such tests have revealed moderate-to-large patient differences unexplainable by medication or generalized deficits. For example, self-reported visual perceptual distortions have already longitudinally predicted impending psychosis in large samples. Possibly predictive psychophysical tests include contrast sensitivity, backward masking, collinear facilitation, stereoscopic depth perception, contour integration, visual shape completion, and restricted fixational patterns during free viewing. Possible brain based markers include visual thalamo-cortical hyperconnectivity, decreased gamma band power during visual detection, and reduced occipital P1 amplitudes (EEG) during passive viewing. Promising retinal markers include reduced cone a- and b-wave amplitudes and photopic negative response (ERG). The foregoing assessments are often brief, well-tolerated, simple to administer, and well-described mechanistically. Across all major levels of analysis-from phenomenology to behavior to brain and retinal functioning-visual system assessment could help identify individuals who go on to develop a psychotic disorder.

Spectral Overlays for Reading Difficulties: Oculomotor Function and Reading Efficiency Among Children and Adolescents With Visual Stress.

This study analyzed the effects of spectral overlays on ocular motility during reading among a clinical group of children and adolescents experiencing visual–perceptual distortions of text. We reviewed the records of 323 eye-hospital patients diagnosed with visual stress and divided this participant sample into two age-based cohorts: children ( n = 184; Mean [ M] age = 10.1, standard deviation [ SD] = 1.3 years) and adolescents ( n = 139; M age = 14.6, SD = 1.5 years). We used a Visagraph III Eye-Movement Recording System to record ocular motor efficiency while reading with and without spectral overlays, and we examined the following parameters: (a) Fixations, (b) Regressions, (c) Span of Recognition, (d) Reading Rate, (e) Relative Efficiency, and (f) Comprehension. Our results showed that using one or some combination of 10 participant-selected spectral overlays immediately and significantly ( p < .001) reduced the number of Fixations and Regressions per 100 words, while there were significant ( p < .001) gains in positive factors such as Span of Recognition, Reading Rate, Relative Efficiency, and Comprehension. Our findings indicate that spectral filtering can be an effective tool for helping many young patients who experience visual–perceptual distortions while reading. Future expanded research employing eye-tracking technology is clearly needed.

Propiedades psicométricas de la escala perceptual de Lectura Irlen en población infantil ecuatoriana

Los profesionales Irlen alrededor del mundo han venido utilizando la Escala Perceptual de Lectura Irlen (EPLI) como instrumento de valoración en la determinación de la presencia de Malestares Físicos al Leer (MFL) y Distorsiones Visuales Perceptuales (DVP) en diferentes poblaciones, sin embargo, se presentan varios cuestionamientos sobre su validez y fiabilidad. El objetivo principal de este estudio fue precisamente analizar las propiedades psicométricas de la sección 1 del EPLI por medio del análisis factorial y el alfa de Cronbach en una población infantil ecuatoriana. Los participantes fueron 409 escolares de 7 a 11 años de la zona urbana de Cuenca, Ecuador. Los resultados apuntan a que las dos dimensiones teóricas de MFL y DVP se comportan como cinco sub-dimensiones empíricas que respetan y se acomodan a estas dos dimensiones teóricas. Estos datos ayudan al mejoramiento tanto del diagnóstico del Síndrome Irlen (SI) como de la intervención en estos malestares y dificultades con el Método Irlen (MI).

A Delphi study to develop practical diagnostic guidelines for visual stress (pattern-related visual stress)

PurposeVisual stress (VS) is characterised by symptoms of visual perceptual distortions and eyestrain when viewing text, symptoms that are alleviated by individually prescribed coloured filters. A recent review supports the existence of VS and its treatment, but noted that controversy remains, in part due to inconsistencies in the diagnosis of the condition. The present paper reviews the diagnostic criteria for VS in the literature and reports a Delphi analysis of the criteria currently used in clinical practice. MethodsTwenty-six eyecare practitioners were invited to participate in a Delphi study. They were selected because they were frequent prescribers of precision tinted lenses. In the first round they were sent a list of the indicators for which there is literature to suggest a relevance in the diagnosis of VS. The practitioners were invited to rank the indicators and add any additional criteria they use in diagnosis. In the second round a revised list was circulated, including items added from the responses in the first round. ResultsThe respondents included optometrists, orthoptists and opticians. In the first round the response rate was 85%. Ninety-one percent of those who participated in the first round also responded in the second round. Strong indicators in the second round included the symptom of words moving when reading, voluntary use of an overlay for a prolonged period, improved performance of ≥15% with an overlay on the Wilkins Rate of Reading test, and an abnormally high score on the Pattern Glare Test. ConclusionsThe strongest diagnostic criteria are combined in a diagnostic tool. This is proposed as a guide for clinical practice and further research.

A systematic review of controlled trials on visual stress using Intuitive Overlays or the Intuitive Colorimeter

Claims that coloured filters aid reading date back 200 years and remain controversial. Some claims, for example, that more than 10% of the general population and 50% of people with dyslexia would benefit from coloured filters lack sound evidence and face validity. Publications with such claims typically cite research using methods that have not been described in the scientific literature and lack a sound aetiological framework.Notwithstanding these criticisms, some researchers have used more rigorous selection criteria and methods of prescribing coloured filters that were developed at a UK Medical Research Council unit and which have been fully described in the scientific literature. We review this research and disconfirm many of the more extreme claims surrounding this topic. This literature indicates that a minority subset of dyslexics (circa 20%) may have a condition described as visual stress which most likely results from a hyperexcitability of the visual cortex. Visual stress is characterised by symptoms of visual perceptual distortions, headaches, and eyestrain when viewing repetitive patterns, including lines of text. This review indicates that visual stress is distinct from, although sometimes co-occurs with, dyslexia. Individually prescribed coloured filters have been shown to improve reading performance in people with visual stress, but are unlikely to influence the phonological and memory deficits associated with dyslexia and therefore are not a treatment for dyslexia.This review concludes that larger and rigorous randomised controlled trials of interventions for visual stress are required. Improvements in the diagnosis of the condition are also a priority.

The effect of viewing distance on responses to the pattern glare test

BackgroundWe investigated whether symptoms of pattern glare were affected by viewing distance, as distinct from spatial frequency, because of an association between symptoms and anomalies of accommodation and vergence.MethodsOne hundred young adults viewed gratings with spatial frequencies of 0.3, 2.3 and 9.4-cycles per degree (cpd) at four test distances (0.4, 0.8, 1.6 and 3.2 metres). Participants were asked to grade the presence of 15 symptoms of visual perceptual distortions and discomfort, on a scale from zero (no symptoms) to 10 (maximum perceptual and somatic symptoms).ResultsThe viewing distance did not affect the nature and strength of symptoms, when viewing gratings with similar spatial frequencies. The symptoms increased with spatial frequency (p < 0.008 for all comparisons).ConclusionsThe symptoms from the Pattern Glare Test do not appear to be modulated by the changes in accommodation and vergence associated with viewing distance, at least in an unselected sample of students. The highest spatial frequency of the current Pattern Glare Test was 9.4-cpd at 0.4 metre and this is insufficiently high to measure the reduction in symptoms at high spatial frequencies. If assessing relative aversion to gratings of different spatial frequencies, it may be useful to increase the testing distance to 0.6 metre so as to increase the spatial frequency of the third grating to 14.2-cpd.

Boundaries of the Psychosis Phenotype

Since Emil Kraepelin classified psychosis into 3 major categories (organic, affective, and schizophrenic) in the late 19th century, the unitary concept of psychosis was abandoned. This categorical conceptualization of psychosis was more or less accepted by clinicians through the 20th century with some refinements. During my residency training, teachers would highlight qualitative differences in reality distortions across disorders; for instance, unusual visual perceptual distortions associated with substance abuse or the affective tone of delusional thinking in psychosis associated with bipolar illness. Such observations were used to support the categorical view of psychosis and stress phenomenological and biological differences in psychosis across various major psychotic disorders. In the past several years, extensive epidemiological and clinical research has yielded information that challenges the categorical models of psychosis. Epidemiological studies of self-reported psychotic symptoms of hallucinations and delusions show that about a quarter of the general population endorse such symptoms. Multivariate taxometric analyses of these epidemiological survey data suggest a dimensional rather than taxonomic structure for these psychotic experiences.1 Within this dimensional model of psychosis, symptoms vary in severity with most persistent and severe psychosis needing treatment (see Jim van Os and Richard Linscott in the current issue2). There is no discontinuity of psychosis across major psychotic disorders such as schizophrenia and bipolar disorders, although the frequency of symptoms and severity may vary. Less severe symptoms may indicate vulnerability to develop schizophrenia or bipolar disorder or even the prodromal phase particularly in individuals with a family history of these disorders. The dimensional model further posits that the underlying biological underpinnings are uniform. This thesis is supported by neurocognitive and neurophysiological findings in individuals with schizotypal personality disorders, with magical thinking, perceptual distortions, and rare hallucinations indicating the lower end of the psychosis dimension. Furthermore, the dimensional model would suggest that psychotic symptoms occurring in different psychiatric disorders such schizophrenia and bipolar disorder share the same neurobiology and etiological factors. The hypothesis of an extensive overlap in the phenomenology and etiopathophysiology of psychosis occurring across different disorders is a fundamental challenge to the Kraepelinian conceptualization of major psychotic disorders. Several lines of evidence support this hypothesis: phenomenological similarities in psychosis across disorders are frequently observed in clinical practice. Slight qualitative differences in reality distortions can easily be due to the modulating effects of the other features of the disorder. For instance, depressed or elated mood may modulate the expression of psychotic symptoms in affective illness. Studies have extensively compared brain function and structure in order to define the underlying neurobiology of psychosis in different conditions. Findings suggest a large overlap in cognitive impairments in schizophrenia and psychotic affective disorders.3 Similarly, sensory gating, sensory-motor gating, eye tracking, and other information processing impairments known to mark schizophrenia liability are frequently observed in other psychotic disorders.4 Brain imaging studies show some overlap but there are significant differences brain structure between schizophrenia and bipolar disorder.5 Most of these findings come from studies in patient cohorts that support the notion of shared neurobiology, but very few studies compare neurobiology among nonill relatives of psychotic disorders. Similar neurobiological findings in relatives of probands with different psychotic disorders would implicate shared etiological, likely genetic, factors. The Bipolar and Schizophrenia Network on Intermediate Phenotypes (B-SNIP) was organized specifically to address this issue. The consortium has recruited about a thousand families of schizophrenia and bipolar disorder with psychosis probands and administered a comprehensive battery that includes cognitive, neurophysiological, and brain imaging measures. Findings from this project will clarify the extent of overlap in the etiopathophysiology of psychosis in schizophrenia and bipolar disorders. Previous genetic studies have identified several linkage “hot-spots” (such as 18p11, 22q11, 13q32, 10p14, and 1q32) and candidate genes (such as DISC1, NRG1, Dysbindin, NOS1, GRM4, and G30/G72) that are implicated both in schizophrenia and bipolar disorder.6 Together, these data suggest psychotic symptoms that occur in different conditions are in most part similar in phenomenology, neurobiology, and etiology. However, studies have also found significant differences in brain function and structure between schizophrenia and bipolar disorder cohorts. These findings may be driven by unique aspects of each of these disorders. For instance, neurobiology associated with the affective component of the bipolar disorder, or the primary negative symptoms in schizophrenia, may explain the differences found in neurobiology between the 2 disorders. Studies similar to the B-SNIP project that also include families of probands with nonpsychotic bipolar and schizoid disorders are needed to clarify to what extent the neurobiology of psychosis is uniform across disorders.

Creating effective focus cues in multi-plane 3D displays

Focus cues are incorrect in conventional stereoscopic displays. This causes a dissociation of vergence and accommodation, which leads to visual fatigue and perceptual distortions. Multi-plane displays can minimize these problems by creating nearly correct focus cues. But to create the appearance of continuous depth in a multi-plane display, one needs to use depth-weighted blending: i.e., distribute light intensity between adjacent planes. Akeley et al. [ACM Trans. Graph. 23, 804 (2004)] and Liu and Hua [Opt. Express 18, 11562 (2009)] described rather different rules for depth-weighted blending. We examined the effectiveness of those and other rules using a model of a typical human eye and biologically plausible metrics for image quality. We find that the linear blending rule proposed by Akeley and colleagues [ACM Trans. Graph. 23, 804 (2004)] is the best solution for natural stimuli.

Educational implications of Meares-Irlen syndrome

Meares-Irlen syndrome can be defined as the inability to see comfortably due to visual perceptual distortions. The condition is also known as visual stress or scotopic sensitivity syndrome. The condition is difficult to diagnose as the child or young person is often unaware of it. However, it can have serious consequences on educational achievement and it is crucial that educationalists and school nurses are aware of the symptoms.

Analysis of the multidimensionality of hallucination-like experiences in clinical and nonclinical Spanish samples and their relation to clinical symptoms: Implications for the model of continuity

Numerous studies have found that hallucinatory experiences occur in the general population. But to date, few studies have been conducted to compare clinical and nonclinical groups across a broad array of clinical symptoms that may co-occur with hallucinations. Likewise, hallucination-like experiences are measured as a multidimensional construct, with clinical and subclinical components related to vivid daydreams, intrusive thoughts, perceptual disturbance, and clinical hallucinatory experiences. Nevertheless, these individual subcomponents have not been examined across a broad spectrum of clinically disordered and nonclinical groups. The goal of the present study was to analyze the differences and similarities in the distribution of responses to hallucination-like experience in clinical and nonclinical populations and to determine the relation of these hallucination-like experiences with various clinical symptoms. These groups included patients with schizophrenia, non-psychotic clinically disordered patients, and a group of individuals with no psychiatric diagnoses. The results revealed that hallucination-like experiences are related to various clinical symptoms across diverse groups of individuals. Regression analysis found that the Psychoticism dimension of the Symptom Check List (SCL-90-R) was the most important predictor of hallucination-like experiences. Additionally, increased auditory and visual hallucination was the only subcomponent that differentiated schizophrenic patients from other groups. This distribution of responses in the dimensions of hallucination-like experiences suggests that not all the dimensions are characteristic of people hearing voices. Vivid daydreams, intrusive thoughts, and auditory distortions and visual perceptual distortions may represent a state of general vulnerability that does not denote a specific risk for clinical hallucinations. Overall, these results support the notion that hallucination-like experiences are closer to a quasi-continuum approach and that total scores on these scales explain a state of vulnerability to general perceptual disturbance.

Posterior visual space perceptual distortions in ecological applications

Posterior visual space perceptual distortions in ecological applications

The Pattern Glare Test: a review and determination of normative values

Pattern glare is characterised by symptoms of visual perceptual distortions and visual stress on viewing striped patterns. People with migraine or Meares-Irlen syndrome (visual stress) are especially prone to pattern glare. The literature on pattern glare is reviewed, and the goal of this study was to develop clinical norms for the Wilkins and Evans Pattern Glare Test. This comprises three test plates of square wave patterns of spatial frequency 0.5, 3 and 12 cycles per degree (cpd). Patients are shown the 0.5 cpd grating and the number of distortions that are reported in response to a list of questions is recorded. This is repeated for the other patterns. People who are prone to pattern glare experience visual perceptual distortions on viewing the 3 cpd grating, and pattern glare can be quantified as either the sum of distortions reported with the 3 cpd pattern or as the difference between the number of distortions with the 3 and 12 cpd gratings, the '3-12 cpd difference'. In study 1, 100 patients consulting an optometrist performed the Pattern Glare Test and the 95th percentile of responses was calculated as the limit of the normal range. The normal range for the number of distortions was found to be <4 on the 3 cpd grating and <2 for the 3-12 cpd difference. Pattern glare was similar in both genders but decreased with age. In study 2, 30 additional participants were given the test in the reverse of the usual testing order and were compared with a sub-group from study 1, matched for age and gender. Participants experienced more distortions with the 12 cpd grating if it was presented after the 3 cpd grating. However, the order did not influence the two key measures of pattern glare. In study 3, 30 further participants who reported a medical diagnosis of migraine were compared with a sub-group of the participants in study 1 who did not report migraine or frequent headaches, matched for age and gender. The migraine group reported more symptoms on viewing all gratings, particularly the 3 cpd grating. The only variable to be significantly different between the groups was the 3-12 cpd difference. In conclusion, people have an abnormal degree of pattern glare if they have a Pattern Glare Test score of >3 on the 3 cpd grating or a score of >1 on the 3-12 cpd difference. The literature suggests that these people are likely to have visual stress in everyday life and may therefore benefit from interventions designed to alleviate visual stress, such as precision tinted lenses.

The relationship between dyslexia and Meares‐Irlen Syndrome

Meares‐Irlen Syndrome (MIS) is characterised by symptoms of visual stress and visual perceptual distortions that are alleviated by using individually prescribed coloured filters. Coloured overlays (sheets of transparent plastic that are placed upon the page) are used to screen for the condition. MIS is diagnosed on the basis of either the sustained voluntary use of an overlay or an immediate improvement (typically of more than 5%) on the Wilkins Rate of Reading Test (WRRT). Various studies are reviewed suggesting a prevalence of 20–34% using these criteria. Stricter criteria give a lower prevalence: for example, 5% of the population read more than 25% faster with an overlay. It has been alleged that MIS is more common in dyslexia, but this has not been systematically investigated. We compared a group of 32 dyslexic with 32 control children aged 7–12 years, matched for age, gender and socio‐economic background. Participants were tested with Intuitive Overlays, and those demonstrating a preference had their rate of reading tested using the WRRT with and without their preferred overlay. Both groups read faster with the overlay, and more so in the dyslexic group. ANOVA revealed no significant effect of group, but a significant improvement in WRRT with overlay (p=0.009) and a significant interaction between group and overlay (p=0.031). We found a similar prevalence of MIS in the general population to that in previous studies and a prevalence in the dyslexic group that was a little higher (odds ratio for &gt;5% criterion: 2.6, 95% confidence limit 0.9–7.3). The difference in prevalence in the two groups did not reach statistical significance. We conclude that MIS is prevalent in the general population and possibly a little more common in dyslexia. Children with dyslexia seem to benefit more from coloured overlays than non‐dyslexic children. MIS and dyslexia are separate entities and are detected and treated in different ways. If a child has both problems then they are likely to be markedly disadvantaged and they should receive prompt treatments appropriate to the two conditions. It is recommended that education professionals as well as eye‐care professionals are alert to the symptoms of MIS and that children are screened for this condition, as well as for other visual anomalies.

The need for optometric investigation in suspected Meares–Irlen syndrome or visual stress

Meares-Irlen syndrome is characterised by symptoms of eye strain, headaches and visual perceptual distortions when viewing text. The symptoms are alleviated with individually prescribed coloured filters, such as precision tinted lenses. Meares-Irlen syndrome, and the related condition of visual stress, are likely to result from hyperexcitability of the visual cortex, which can also occur in migraine. The symptoms of Meares-Irlen syndrome and visual stress are non-specific and the condition needs to be differentially diagnosed from other optometric conditions, such as refractive error, binocular vision anomalies, and accommodative anomalies. Three case reports are described of patients who consulted the author with suspected Meares-Irlen syndrome but were found to have other causes for their symptoms: posterior sub-capsular cataract, high uncorrected astigmatism, and decompensated convergence weakness exophoria. These cases highlight the need for professional eye care for people with suspected Meares-Irlen syndrome. Although this advice is stressed in literature on the well-established MRC/Wilkins Intuitive Colorimeter system, it is not always stressed in literature about other systems. This may be a cause for concern.

The effect of coloured filters on the rate of reading in an adult student population.

Meares-Irlen Syndrome is characterised by visual stress (visual discomfort) and visual perceptual distortions that can be alleviated by individually prescribed coloured filters. The benefit from coloured filters can be demonstrated with the Wilkins Rate of Reading Test (WRRT). Previous research using individually prescribed coloured overlays (sheets of plastic placed on a page) found that between one-fifth and one-third of unselected school-children show a significant (> 5%) improvement in their rate of reading with their chosen overlay. This 5% cut-off has good sensitivity and specificity for predicting those children who will continue to voluntarily use their overlay for a sustained period. Previous research has concentrated on children, and we sought to investigate the immediate effect of overlays on rate of reading in an adult population. Subjects were 113 unselected university students who answered a symptom questionnaire and were tested with the Wilkins Intuitive Overlays and WRRT. Some symptoms were common: 73% reported sore or tired eyes when reading and 40% reported four to 12 headaches a year. One hundred of the subjects chose an overlay as improving their immediate perception of text. These subjects were significantly more likely to report perceptual distortions and visual discomfort on viewing text than subjects who did not choose an overlay. The 100 subjects read 3.8% faster with the overlay than without any overlay (p < 0.00001), whereas the 13 subjects who did not choose an overlay read 1.7% slower with a placebo overlay than without (p = 0.37). Of the subjects who chose an overlay, 38% read more than 5% faster with the overlay and 2% read more than 25% faster. These results are comparable with those obtained for children. We conclude that Meares-Irlen Syndrome is likely to be as common in adults as it is in children.

Optometric correlates of Meares—Irlen Syndrome: a matched group study

People who report visual perceptual distortions, typically when reading, that are alleviated by using coloured filters are described as suffering from ‘Meares—Irlen Syndrome’. A recent double-masked placebo-controlled trial showed that this condition cannot be solely explained as a placebo effect and that the beneficial filter is idiosyncratic and sometimes needs to be highly specific. Several mechanisms have been suggested for Meares—Irlen Syndrome including ocular motor (binocular and accommodative) anomalies, a sensitivity to patterned stimuli (pattern glare), and a deficit of the transient visual sub-system. We investigated these hypotheses by comparing 16 children, who reported the symptoms described above and who showed a sustained benefit from coloured filters, with 25 control children who came from the same school and were matched for age, reading performance and intelligence. The ‘Meares—Irlen Syndrome’ group had slightly, but significantly, reduced vergence and accommodative amplitudes and stereo-acuity; they also demonstrated significantly more pattern glare. The two groups did not differ significantly in their visual acuities, refractive error, dissociated or associated heterophoria, AC/A ratio, or ability to perceive 20 Hz flicker. It appears that certain ocular motor factors are correlates of Meares—Irlen Syndrome, rather than the primary underlying cause of the symptoms. The results support the hypothesis that pattern glare may be involved in the mechanism of Meares—Irlen Syndrome.

Optometric correlates of Meares–Irlen Syndrome: a matched group study

People who report visual perceptual distortions, typically when reading, that are alleviated by using coloured filters are described as suffering from 'Meares-Irlen Syndrome'. A recent double-masked placebo-controlled trial showed that this condition cannot be solely explained as a placebo effect and that the beneficial filter is idiosyncratic and sometimes needs to be highly specific. Several mechanisms have been suggested for Meares-Irlen Syndrome including ocular motor (binocular and accommodative) anomalies, a sensitivity to patterned stimuli (pattern glare), and a deficit of the transient visual sub-system. We investigated these hypotheses by comparing 16 children, who reported the symptoms described above and who showed a sustained benefit from coloured filters, with 25 control children who came from the same school and were matched for age, reading performance and intelligence. The 'Meares-Irlen Syndrome' group had slightly, but significantly, reduced vergence and accommodative amplitudes and stereo-acuity; they also demonstrated significantly more pattern glare. The two groups did not differ significantly in their visual acuities, refractive error, dissociated or associated heterophoria, AC/A ratio, or ability to perceive 20 Hz flicker. It appears that certain ocular motor factors are correlates of Meares-Irlen Syndrome, rather than the primary underlying cause of the symptoms. The results support the hypothesis that pattern glare may be involved in the mechanism of Meares-Irlen Syndrome.