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Frequency of Visual Deficits in Children With Developmental Dyslexia
Raghuram A, Gowrisankaran S, Swanson E, Zurakowski D, Hunter D, Waber D. JAMA Ophthalmol 2018,136(10):1089-1095
Background: Developmental dyslexia (DD) is a specific learning disability of neurobiological origin whose core cognitive deficit is widely believed to involve language (phonological) processing. Although reading is also a visual task, the potential role of vision in DD has been controversial, and little is known about the integrity of visual function in individuals with DD.
Aim:  To assess the frequency of visual deficits (specifically vergence, accommodation, and ocular motor tracking) in children with DD compared with a control group of typically developing readers.
Method: A prospective, uncontrolled observational study was conducted from May 28 to October 17, 2016, in an outpatient ophthalmology ambulatory clinic among 29 children with DD and 33 typically developing (TD) children.Primary outcomes were frequencies of deficits in vergence (amplitude, fusional ranges, and facility), accommodation (amplitude, facility, and accuracy), and ocular motor tracking (Developmental Eye Movement test and Visagraph eye tracker).
Results:  Among the children with DD (10 girls and 19 boys; mean [SD] age, 10.3 [1.2] years) and the TD group (21 girls and 12 boys; mean [SD] age, 9.4 [1.4] years), accommodation deficits were more frequent in the DD group than the TD group (16 [55%] vs 3 [9%]; difference = 46%; 95% CI, 25%-67%; P < .001). For ocular motor tracking, 18 children in the DD group (62%) had scores in the impaired range (in the Developmental Eye Movement test, Visagraph, or both) vs 5 children in the TD group (15%) (difference, 47%; 95% CI, 25%-69%; P < .001). Vergence deficits occurred in 10 children in the DD group (34%) and 5 children in the TD group (15%) (difference, 19%; 95% CI, –2.2% to 41%; P = .08). In all, 23 children in the DD group (79%) and 11 children in the TD group (33%) had deficits in 1 or more domain of visual function (difference, 46%; 95% CI, 23%-69%; P < .001).
Conclusion:  These findings suggest that deficits in visual function are far more prevalent in school-aged children with DD than in TD readers, but the possible cause and clinical relevance of these deficits are uncertain. Further study is needed to determine the extent to which treating these deficits can improve visual symptoms and/or reading parameters.


Dyslexia and dyscalculia are characterized by common perception deficits.
Cheng D, Xiao Q, Chen Q, Cui J, Zhou X. Dev Neuropsychol 2018, 43(6):497-507
A number of studies have investigated the cognitive deficits underlying dyslexia and dyscalculia. Yet, it remains unclear as to whether dyslexia and dyscalculia are associated with the common perception deficits. The current investigation analyzed cognitive performance in children with dyslexia, dyscalculia, comorbidity, and typically developing subjects. The results showed that children with dyslexia, dyscalculia and comorbidity exhibited common deficits in numerosity processing and visual perception. Furthermore, visual perception deficits accounted for deficits in numerosity processing in all three groups. The results suggest that perception are a common cognitive deficit underlying both developmental dyslexia and dyscalculia.


Efficacy of vision therapy in children with learning disability and associated binocular vision anomalies.
Hussaindeen JR, Shah P, Ramani KK, Ramanujan L. J Optom 2018, 11(1):40-48
Purpose: To report the frequency of binocular (BV) in children with specific learning disorders (SLD) and to assess the efficacy of vision therapy (VT) in children with a non-strabismic binocular vision anomaly (NSBVA).
Method: The study was carried out at a centre for learning disability (LD). Comprehensive eye examination and binocular vision assessment was carried out for 94 children (mean (SD) age: 15 (2.2) years) diagnosed with specific learning disorder. BV assessment was done for children with best corrected visual acuity of ≥6/9 – N6, cooperative for examination and free from any ocular pathology. For children with a diagnosis of NSBVA (n=46), 24 children were randomized to VT and no intervention was provided to the other 22 children who served as experimental controls. At the end of 10 sessions of vision therapy, BV assessment was performed for both the intervention and non-intervention groups.
Results: Binocular vision anomalies were found in 59 children (62.8%) among which 22% (n=13) had strabismic binocular vision anomalies (SBVA) and 78% (n=46) had a NSBVA. Accommodative infacility (AIF) was the commonest of the NSBVA and found in 67%, followed by convergence insufficiency (CI) in 25%. Post-vision therapy, the intervention group showed significant improvement in all the BV parameters (Wilcoxon signed rank test, p<0.05) except negative fusional vergence.
Conclusion: Children with specific learning disorders have a high frequency of binocular vision disorders and vision therapy plays a significant role in improving the BV parameters. Children with SLD should be screened for BV anomalies as it could potentially be an added hindrance to the reading difficulty in this special population.


Vision screening outcomes of Grade 3 children in Australia: Differences in academic achievement.
White S, Wood J, Black A, Hopkins S. International Journal of Educational Research 2017,83: 154-159
Learning is multisensory, thus impaired vision may impact on classroom learning and subsequently, academic achievement. This research investigated the impact of impaired vision on academic achievement in a sample of 109 Grade 3 Australian children. Approximately 30% of the sample were identified as borderline or unsatisfactory by a vision screening and were referred for a full eye examination. Children who were referred at the vision screening scored significantly lower on national standardised tests of reading, grammar and punctuation, spelling and numeracy, when compared to their not referred peers. This research has important implications for teachers and eye health professionals, as the findings highlight the importance of early vision screening in identifying children who may be achieving below their potential.


The effects of visual attention span and phonological decoding in reading comprehension in dyslexia: A path analysis.
Chen C, Schneps M, Masyn K, Thomsor J. Dyslexia 2016, 22(4):322-344
Increasing evidence has shown visual attention span to be a factor, distinct from phonological skills, that explains single-word identification (pseudo-word/word reading) performance in dyslexia. Yet, little is known about how well visual attention span explains text comprehension. Observing reading comprehension in a sample of 105 high school students with dyslexia, we used a pathway analysis to examine the direct and indirect path between visual attention span and reading comprehension while controlling for other factors such as phonological awareness, letter identification, short-term memory, IQ and age. Integrating phonemic decoding efficiency skills in the analytic model, this study aimed to disentangle how visual attention span and phonological skills work together in reading comprehension for readers with dyslexia. We found visual attention span to have a significant direct effect on more difficult reading comprehension but not on an easier level. It also had a significant direct effect on pseudo-word identification but not on word identification. In addition, we found that visual attention span indirectly explains reading comprehension through pseudo-word reading and word reading skills. This study supports the hypothesis that at least part of the dyslexic profile can be explained by visual attention abilities.


Impaired oculomotor behaviour of children with developmental dyslexia in antisaccades and predictive saccades tasks.
Lukasova K, Silva I, Macedo E. Frontiers in Psychology 2016, 7:987
Analysis of eye movement patterns during tracking tasks represents a potential way to identify differences in the cognitive processing and motor mechanisms underlying reading in dyslexic children before the occurrence of school failure. The current study aimed to evaluate the pattern of eye movements in antisaccades, predictive saccades and visually guided saccades in typical readers and readers with developmental dyslexia. The study included 30 children (age M = 11; SD = 1.67), 15 diagnosed with developmental dyslexia (DG) and 15 regular readers (CG), matched by age, gender and school grade. Cognitive assessment was performed prior to the eye-tracking task during which both eyes were registered using the Tobii® 1750 eye-tracking device. The results demonstrated a lower correct antisaccades rate in dyslexic children compared to the controls (p < 0.001, DG = 25%, CC = 37%). Dyslexic children also made fewer saccades in predictive latency (p < 0.001, DG = 34%, CG = 46%, predictive latency within −300–120 ms with target as 0 point). No between-group difference was found for visually guided saccades. In this task, both groups showed shorter latency for right-side targets. The results indicated altered oculomotor behavior in dyslexic children, which has been reported in previous studies. We extend these findings by demonstrating impaired implicit learning of target’s time/position patterns in dyslexic children


The prevalence of poor ocular motilities in a mainstream school compared to two learning-disabled schools in Johannesburg: original research.
Metsing IT, Ferreira JT. African Vision and Eye Health 2016, 75(1):1-6
Background: Ocular motilities play a major role when reading for the continuous acquisition and updating of visually presented information. Accurate oculomotor control is required to be able to learn how to read and to efficiently read to learn. This process requires accurate decoding accomplished by precise oculomotor control.
Aim: A comparison of the prevalence of poor ocular motilities between mainstream and learning-disabled schools were explored from three different schools; one mainstream and two disabled schools. One hundred and ninety-two children, age range 8-13 years (mean = 10.30, s.d.: ± 0.999) in grades 3 and 4, with 112 children from the two learning-disabled schools and 80 children from the mainstream school participated in the study.
Method: The standardised direct observation test, using the Northeastern State University College of Optometry scoring criteria, was used to evaluate saccadic and pursuit eye movements. Fixation maintenance was evaluated using the Southern California College of Optometry scoring criteria. The Gulden fixation stick with a 6/24 letter E was used as a fixation target.
Results: The results showed that children from the learning-disabled schools appeared to have a higher incidence of poor saccadic accuracy compared with children from the mainstream school. No significant associations in both the mainstream and the learning-disabled children were found for head movements, pursuits and fixation ability. However, the results suggest a statistically significant association between poor saccadic accuracy and children from the learning-disabled schools.
Conclusion: This study provides further evidence for a link between poor saccadic accuracy and children from the school of the learning disabled.


Visual and auditory perception in preschool children at risk for dyslexia.
Ortiz R, Estevez A, Muneton M, Dominguez C. Research in Developmental Disabilities 2014, 35(11):2673-2680.
Recently, there has been renewed interest in perceptive problems of dyslexics. A polemic research issue in this area has been the nature of the perception deficit. Another issue is the causal role of this deficit in dyslexia. Most studies have been carried out in adult and child literates; consequently, the observed deficits may be the result rather than the cause of dyslexia. This study addresses these issues by examining visual and auditory perception in children at risk for dyslexia. We compared children from preschool with and without risk for dyslexia in auditory and visual temporal order judgment tasks and same–different discrimination tasks. Identical visual and auditory, linguistic and nonlinguistic stimuli were presented in both tasks. The results revealed that the visual as well as the auditory perception of children at risk for dyslexia is impaired. The comparison between groups in auditory and visual perception shows that the achievement of children at risk was lower than children without risk for dyslexia in the temporal tasks. There were no differences between groups in auditory discrimination tasks. The difficulties of children at risk in visual and auditory perceptive processing affected both linguistic and nonlinguistic stimuli. Our conclusions are that children at risk for dyslexia show auditory and visual perceptive deficits for linguistic and nonlinguistic stimuli. The auditory impairment may be explained by temporal processing problems and these problems are more serious for processing language than for processing other auditory stimuli. These visual and auditory perceptive deficits are not the consequence of failing to learn to read, thus, these findings support the theory of temporal processing deficit.


Spatial and temporal attention in developmental dyslexia.
Ruffino M, Gori S, Boccardi D, Molteni M, Facoetti A. Front Hum Neurosci. 2014, 8: 331.
Although the dominant view posits that developmental dyslexia (DD) arises from a deficit in phonological processing, emerging evidence suggest that DD could result from a more basic cross-modal letter-to-speech sound integration deficit. Letters have to be precisely selected from irrelevant and cluttering letters by rapid orienting of visual attention before the correct letter-to-speech sound integration applies. In the present study the time-course of spatial attention was investigated measuring target detection reaction times (RTs) in a cuing paradigm, while temporal attention was investigated by assessing impaired identification of the first of two sequentially presented masked visual objects. Spatial and temporal attention were slower in dyslexic children with a deficit in pseudoword reading (N = 14) compared to chronological age (N = 43) and to dyslexics without a deficit in pseudoword reading (N = 18), suggesting a direct link between visual attention efficiency and phonological decoding skills. Individual differences in these visual attention mechanisms were specifically related to pseudoword reading accuracy in dyslexics. The role of spatial and temporal attention in the graphemic parsing process might be related to a basic oscillatory “temporal sampling” dysfunction.


The role of visual processing speed in reading speed development.
Lobier M, Dubois M, Valdois S. PLoS ONE 2013, 8(4).
A steady increase in reading speed is the hallmark of normal reading acquisition. However, little is known of the influence of visual attention capacity on children’s reading speed. The number of distinct visual elements that can be simultaneously processed at a glance (dubbed the visual attention span), predicts single-word reading speed in both normal reading and dyslexic children. However, the exact processes that account for the relationship between the visual attention span and reading speed remain to be specified. We used the Theory of Visual Attention to estimate visual processing speed and visual short-term memory capacity from a multiple letter report task in eight and nine year old children. The visual attention span and text reading speed were also assessed. Results showed that visual processing speed and visual short term memory capacity predicted the visual attention span. Furthermore, visual processing speed predicted reading speed, but visual short term memory capacity did not. Finally, the visual attention span mediated the effect of visual processing speed on reading speed. These results suggest that visual attention capacity could constrain reading speed in elementary school.


A causal link between visual spatial attention and reading acquisition.
Franceshini S, Gori S, Ruffino M, Pedrolli K, Facoetti A. Current Biology 2012, 22(9):814-819.
Reading is a unique, cognitive human skill crucial to life in modern societies, but, for about 10% of the children, learning to read is extremely difficult. They are affected by a neurodevelopmental disorder called dyslexia. Although impaired auditory and speech sound processing is widely assumed to characterize dyslexic individuals, emerging evidence suggests that dyslexia could arise from a more basic cross-modal letter-to-speech sound integration deficit. Letters have to be precisely selected from irrelevant and cluttering letters by rapid orienting of visual attention before the correct letter-to-speech sound integration applies. Here we ask whether prereading visual parietal-attention functioning may explain future reading emergence and development. The present 3 year longitudinal study shows that prereading attentional orienting—assessed by serial search performance and spatial cueing facilitation—captures future reading acquisition skills in grades 1 and 2 after controlling for age, nonverbal IQ, speech-sound processing, and nonalphabetic cross-modal mapping. Our findings provide the first evidence that visual spatial attention in preschoolers specifically predicts future reading acquisition, suggesting new approaches for early identification and efficient prevention of dyslexia.


Relating vision status to academic achievment among year-2 school children in Malaysia.
Chen A, Bleything W, Lim Y. J Am Optom Assoc. 2011 May;82(5):267-273.
Background: Vision affects daily activities, but of particular importance is the impact upon the learning process. Many studies have been conducted to establish the relationship between vision problems and academic performance. The results are varied, however, and suggest additional research is needed with particular care given to study design.
Methods: This study included 1,103 year-2 school children enrolled in 7 public schools in the Klang Valley region of Malaysia. There were an equal proportion of males (50.6%) and females (49.4%). The testing battery was designed to assess visual acuity, ocular muscle balance, visual analysis skills, visual-spatial skills, and visual-motor integration skills.
Results: Children with average and above-average achievement showed a different visual performance profile from those children with low academic achievement. They had a statistically significant better pass rate in physical aspects (visual acuity), physiological aspects (ocular motor balance), and perceptual aspects (visual-motor integration/visual-spatial and visual-analysis skills).
Conclusion: Children with low academic achievement are more likely to exhibit problems in visual acuity, ocular motor balance, visual-motor integration and most all components of visual analysis skills. This finding supports the concept that visual performance is key to learning and therefore of chief concern as to school achievement.


Visual spatial attention and speech segmentation are both impaired in preschoolers at familial risk for developmental dyslexia.
Facoetti A, Trussardi AN, Ruffino M, Gori S, Zorzi M. Dyslexia 2010, 16(3):226-3.
Phonological skills are foundational of reading acquisition and impaired phonological processing is widely assumed to characterize dyslexic individuals. However, reading by phonological decoding also requires rapid selection of sublexical orthographic units through serial attentional orienting, and recent studies have shown that visual spatial attention is impaired in dyslexic children. Our study investigated these different neurocognitive dysfunctions, before reading acquisition, in a sample of preschoolers including children with (N=20) and without (N=67) familial risk for developmental dyslexia. Children were tested on phonological skills, rapid automatized naming, and visual spatial attention. At-risk children presented deficits in both visual spatial attention and syllabic segmentation at the group level. Moreover, the combination of visual spatial attention and syllabic segmentation scores was more reliable than either single measure for the identification of at-risk children. These findings suggest that both visuo-attentional and perisylvian-auditory dysfunctions might adversely affect reading acquisition, and may offer a new approach for early identification and remediation of developmental dyslexia.

Dyslexia: a deficit in visuo-spatial attention, not in phonological processing.
Vidyasagar TR, Pammer K. Trends Cogn Sci. 2010, Feb;14(2):57-63.
Developmental dyslexia affects up to 10 per cent of the population and it is important to understand its causes. It is widely assumed that phonological deficits, that is, deficits in how words are sounded out, cause the reading difficulties in dyslexia. However, there is emerging evidence that phonological problems and the reading impairment both arise from poor visual (i.e., orthographic) coding. We argue that attentional mechanisms controlled by the dorsal visual stream help in serial scanning of letters and any deficits in this process will cause a cascade of effects, including impairments in visual processing of graphemes, their translation into phonemes and the development of phonemic awareness. This view of dyslexia localizes the core deficit within the visual system and paves the way for new strategies for early diagnosis and treatment.

Influence of the visual attention span on child reading performance: a cross sectional study.
Bosse M, Vladois S. Journal of Research in Reading 2009, 32(2):230-253.
The visual attention (VA) span deficit hypothesis was found successfully to account for variability in developmental dyslexia (Bosse, Tainturier & Valdois, 2007). We conducted a cross-sectional study on 417 typically developing children from first, third and fifth grades examining the role of VA span on the development of reading skills. A battery including reading, phoneme awareness and VA span tasks was administered. Results show that VA span predicts variations in learning to read independent of the influence of phoneme awareness. Moreover, whereas the specific influence of VA span on pseudoword reading declines from first to third grade, VA span has a significant and sustained influence across grades for the irregular words. In addition to phoneme awareness, the VA span contributes to reading performance from the beginning of literacy instruction, suggesting that it might have a long-term influence on specific orthographic knowledge acquisition.

Developmental dyslexia: the visual attention span deficit hypothesis.
Bosse ML, Tainturier MJ, Valdois S. Cognition. 2007, Aug;104(2):198-230.
The visual attention (VA) span is defined as the amount of distinct visual elements which can be processed in parallel in a multi-element array. Both recent empirical data and theoretical accounts suggest that a VA span deficit might contribute to developmental dyslexia, independently of a phonological disorder. In this study, this hypothesis was assessed in two large samples of French and British dyslexic children whose performance was compared to that of chronological-age matched control children. Results of the French study show that the VA span capacities account for a substantial amount of unique variance in reading, as do phonological skills. The British study replicates this finding and further reveals that the contribution of the VA span to reading performance remains even after controlling IQ, verbal fluency, vocabulary and single letter identification skills, in addition to phoneme awareness. In both studies, most dyslexic children exhibit a selective phonological or VA span disorder. Overall, these findings support a multi-factorial view of developmental dyslexia. In many cases, developmental reading disorders do not seem to be phonological disorders. We propose that a VA span deficit is a likely alternative underlying cognitive deficit in dyslexia.


Is there a common linkage among reading comprehension, visual attention, and magnocellular processing?
Solan HA, Shelley-Tremblay JF, Hansen PC, Larson S. J Learn Disabil. 2007, 40(3):270-8.
The authors examined the relationships between reading comprehension, visual attention, and magnocellular processing in 42 Grade 7 students. The goal was to quantify the sensitivity of visual attention and magnocellular visual processing as concomitants of poor reading comprehension in the absence of either vision therapy or cognitive intervention. Nineteen good readers (M = grade equivalent of 11.2) and 23 poor readers (M = grade equivalent of 3.5) were identified. Participants were tested for visual attention skills (Cognitive Assessment System: CAS) and magnocellular integrity (Coherent Motion Threshold: CM). Individual and combined correlations of dependent variables with reading were significant at the 0.01 level. When combined, the two tests (CAS + CM) accounted for 61% of the variance in reading comprehension. Logistic regression analysis measured sensitivity of the two diagnostic tests. Attention tests correctly classified 95.7% of poor readers, and coherent motion correctly classified 78.3% of poor readers. When the data were combined, 91.3% of poor readers were correctly classified. The research reinforces the notion that a common linkage exists between reading comprehension, visual attention, and magnocellular processing. Diagnostic test batteries for students who have been identified as reading disabled should include magnocellular and visual attention tests. Procedures to diagnose and ameliorate these disabilities are discussed.


Vision, Visual-Information Processing, and Academic Performance Among Seventh-Grade Schoolchildren: A More Significant Relationship Than We Thought?
Goldstand S, Koslowe K, Parush S. American Journal of Occupational Therapy, 2005, 59 (4): 377-389.
Objective: To compare visual and visual-information processing skills between children with and without mild reading and academic problems and examine the incidence of visual deficits among them.
Method: Seventy-one seventh graders classified as proficient (n = 46) and nonproficient (n = 25) readers were compared with respect to scores on an accepted vision screening, on tests of visual-perception, visual-motor integration, and academic performance. Further, academic performance and visual-information processing were compared between children who failed and passed the vision screening.
Results: Visual deficits were found in 68% of the participants, and among significantly more boys than girls. Nonproficient readers had significantly poorer academic performance and vision-screening scores than the proficient readers. Participants who passed the visual screening performed significantly better in visual perception than those who failed.
Conclusion: Visual function significantly distinguishes between children with and without mild academic problems, as well as on visual-perception scores. The high occurrence of visual deficits among participants warrants consideration of vision deficits among schoolchildren with academic performance difficulties.


Does a visual-orthographic deficit contribute to reading disability?
Badian N. Annals of Dyslexia 2005,55(1):28-52.
In this study, visual-orthographic skills were defined as the ability to recognize whether letters and numerals are correctly oriented. Aims were to investigate whether visual-orthographic skills would contribute independent variance to reading, and whether children with a visual-orthographic deficit would be more impaired readers than similar children without this deficit. Participants were 207 children, aged 8 to 10 years, who attended school in a small suburban community. Because of the evidence that phonological awareness and naming speed are strongly related to reading, visual-orthographic skills were entered into hierarchical regression analyses following these variables. With age, verbal IQ, and verbal short-term memory also controlled, visual-orthographic skills accounted for significant independent variance in all reading measures. When children with a visual- orthographic deficit (29% of the sample) were compared with those without this deficit, they were significantly lower on all reading variables. At 8 to 10 years of age, reading progress of some children continues to be hampered by a problem in orthographic memory for the orientation of letters and numerals. Such children will require special attention, but their problems may be overlooked. As recommended by Willows and Terepocki (1993), there is need for further research on the phenomenon of letter reversals when they occur among children beyond first grade.


Voluntary control of saccadic and smooth-pursuit eye movements in children with learning disorders.
Fukushima J, Tanaka S, Williams JD, Fukushima K. Brain and Development 2005, 27(8): 579-588.
Eye movement is crucial to humans in allowing them to aim the foveae at objects of interest. We examined the voluntary control of saccadic and smooth-pursuit eye movements in 18 subjects with learning disorders (LDs) (aged 8-16) and 22 normal controls (aged 7-15). The subjects were assigned visually guided, memory-guided, and anti-saccade tasks, and smooth-pursuit eye movements (SPEM). Although, the LD subjects showed normal results in the visually guided saccade task, they showed more errors in the memory-guided saccade task (e.g. they were unable to stop themselves reflexively looking at the cue) and longer latencies, even when they performed correctly. They also showed longer latencies than the controls in the anti-saccade task. These results suggest that they find it difficult to voluntarily suppress reflexive saccades and initiate voluntary saccades when a target is invisible. In SPEM using step-ramp stimuli, the LD subjects showed lower open- and closed-loop gains. These results suggest disturbances of both acceleration of eye movement in the initial state and maintenance of velocity in minimizing retinal slip in the steady state. Recent anatomical studies in LD subjects have suggested abnormalities in the structure of certain brain areas such as the frontal cortex. Frontal eye movement-related areas such as the frontal eye fields and supplementary eye fields may be involved in these disturbances of voluntary control of eye movement in LDs.


Spatial load factor in prediction of reading performance.
Larter SC, Herse PR, Naduvilath TJ, Dain SJ. Ophthalmic Physiol Opt 2004, 24(5):440-449.
This study investigated whether there is a relationship between reading age and clinical optometric tests that have varying degrees of spatial loading in their design. Spatial loading in this context is the demand on the visual system to process information about the relative position and orientation of stimuli. A total of 112 children aged 8-11 years were assessed using saccadic eye movement and rapid naming tasks with varying spatial loads. All were subtests of Garzia’s Developmental Eye Movement test and Liubinas’ SeeRite Reading Diagnostic Programme. Variability in load was achieved by comparing rapid naming of numerals vs the spatially loaded letters p, d, b, q; and by comparing the speed of reading numerals presented in increasingly complex arrays. Reading Age was assessed independently and results were analysed by multiple logistic regression. Spatially loaded naming tasks performed at speed exposed a Spatial Loading Factor which clearly differentiates children at risk with reading.


Deficient saccadic inhibition in Asperger’s disorder and the social-emotional processing disorder.
Manoach DS, Lindgren KA, Barton JJS. Journal of Neurology and Neurosurgery and Psychiatry 2004, 75:1719-1726.
Background: Both Asperger’s disorder and the social-emotional processing disorder (SEPD), a form of non-verbal learning disability, are associated with executive function deficits. SEPD has been shown to be associated with deficient saccadic inhibition.
Objective: To study two executive functions in Asperger’s disorder and SEPD, inhibition and task switching, using a single saccadic paradigm.
Methods: 22 control subjects and 27 subjects with developmental social processing disorders-SEPD, Asperger’s disorder, or both syndromes-performed random sequences of prosaccades and antisaccades. This design resulted in four trial types, prosaccades and antisaccades, that were either repeated or switched. The design allowed the performance costs of inhibition and task switching to be isolated.
Results: Subjects with both Asperger’s disorder and SEPD showed deficient inhibition, as indicated by increased antisaccade errors and a disproportionate increase in latency for antisaccades relative to prosaccades. In contrast, task switching error and latency costs were normal and unrelated to the costs of inhibition.
Conclusion: This study replicates the finding of deficient saccadic inhibition in SEPD, extends it to Asperger’s disorder, and implicates prefrontal cortex dysfunction in these syndromes. The finding of intact task switching shows that executive function deficits in Asperger’s disorder and SEPD are selective and suggests that inhibition and task switching are mediated by distinct neural networks.


Are the results of the Berry-Buktenica Development test of visual-motor integration and its subtests related to academic achievement test scores?
Sortor JM, Kulp MT. Optom Vis Sci 2003, 80(11):758-763.
Purpose: Although visual analysis, motor coordination, and visual-motor integration can each affect performance on a test of visual motor integration, previous studies have not reported the relative importance of these components to the relation between visual motor integration and learning readiness, reading, and math. This investigation relates academic achievement in reading and math to performance on the Beery-Buktenica Developmental Test of Visual-Motor Integration (VMI) and its subtests, Visual Perception and Motor Coordination.
Methods: The VMI was administered to 155 children in second through fourth grades (7 to 10 years of age; mean, 8.4 +/- 1.0 years). The Otis-Lennon School Ability Test and Stanford Achievement Test were administered by the school.
Results: A significant difference was found in performance on the VMI and Visual Perception and Motor Coordination subtests between children in the upper and lower quartiles in reading (p = 0.020, p < 0.001, and p = 0.027, respectively) and math achievement (p = 0.004, p < 0.001, and p = 0.01, respectively). The VMI standard score was significantly correlated with Stanford total math standard score (p = 0.001) and a trend toward significance was found for Stanford reading score (p = 0.050) while partially controlling for verbal school ability and age. In addition, Visual Perception and Motor Coordination standard scores were significantly related to Stanford math (p < 0.001 and p = 0.005, respectively) and reading score (p = 0.008 and p = 0.027, respectively) after partially controlling for verbal school ability and age. Multiple linear regressions controlling for performance on the VMI and each subtest, as well as age and verbal cognitive ability, showed a significant relation between the Visual Perception subtest score and math achievement.
Conclusion: Visual perceptual ability should be assessed in children with poor math and/or reading achievement


Clock drawing in developmental dyslexia.
Eden GF, Wood FB, Stein JF. Journal of Learning Disabilities 2003, 36(3):216-228.
Although developmental dyslexia is often defined as a language-based reading impairment not attributable to low intelligence or educational or socioeconomic limitations, the behavioral manifestations of dyslexia are not restricted to the realm of language. Functional brain imaging studies have shed light on physiological differences associated with poor reading both inside and outside the classical language areas of the brain. Concurrently, clinically useful tests that elicit these nonlinguistic deficits are few. Specifically, the integrity of the dorsal visual pathway, which predominantly projects to the parietal cortex, remains underinvestigated, lacking easily administered tests. Here we present the Clock Drawing Test (CDT), used to test the visuoconstructive ability of children with and without dyslexia and garden-variety poor readers. Compared to typically reading children, many children with dyslexia and some garden-variety poor readers showed significant left neglect, as measured by the distribution of figures drawn on the left clock face. In the poor readers with dyslexia, we observed spatial construction deficits like those of patients with acquired right-hemisphere lesions. The results suggest that in some children with dyslexia, right-hemisphere dysfunction may compound the phonological processing deficits attributed to the left hemisphere. The CDT provides an easy opportunity to assess skills known to be associated with right-hemisphere parietal function. This test can be easily administered to children for both clinical and research purposes.


Altered control of visual fixation and saccadic eye movements in attention-deficit hyperactivity disorder.
Munoz DP, Armstrong IT, Hampton KA, Moore KD. Neurophyisol 2003, 10:1152.
Attention-deficit hyperactivity disorder (ADHD) is characterized by the overt symptoms of impulsiveness, hyperactivity, and inattention. A frontostriatal pathophysiology has been hypothesized to produce these symptoms and lead to reduced ability to inhibit unnecessary or inappropriate behavioral responses. Oculomotor tasks can be designed to probe the ability of subjects to generate or inhibit reflexive and voluntary responses. Because regions of the frontal cortex and basal ganglia have been identified in the control of voluntary responses and saccadic suppression, we hypothesized that children and adults diagnosed with ADHD may have specific difficulties in oculomotor tasks requiring the suppression of reflexive or unwanted saccadic eye movements. To test this hypothesis, we measured eye movement performance in pro- and anti-saccade tasks of 114 ADHD and 180 control participants ranging in age from 6 to 59 yr. In the pro-saccade task, participants were instructed to look from a central fixation point toward an eccentric visual target. In the anti-saccade task, stimulus presentation was identical, but participants were instructed to suppress the saccade to the stimulus and instead look from the central fixation point to the side opposite the target. The state of fixation was manipulated by presenting the target either when the central fixation point was illuminated (overlap condition) or at some time after it disappeared (gap condition). In the pro-saccade task, ADHD participants had longer reaction times, greater intra-subject variance, and their saccades had reduced peak velocities and increased durations. In the anti-saccade task, ADHD participants had greater difficulty suppressing reflexive pro-saccades toward the eccentric target, increased reaction times for correct anti-saccades, and greater intra-subject variance. In a third task requiring prolonged fixation, ADHD participants generated more intrusive saccades during periods when they were required to maintain steady fixation. The results suggest that ADHD participants have reduced ability to suppress unwanted saccades and control their fixation behavior voluntarily, a finding that is consistent with a fronto-striatal pathophysiology. The findings are discussed in the context of recent neurophysiological data from nonhuman primates that have identified important control signals for saccade suppression that emanate from frontostriatal circuits.


On the relationship between dynamic visual and auditory processing and literacy skills; results from a large primary-school study.
Talcott JB, Witton C, Hebb GS, Stoodley CJ, Westwood EA, France SJ, Hansen PC, Stein JF. Dyslexia. 2002, 8(4): 204-25.
Three hundred and fifty randomly selected primary school children completed a psychometric and psychophysical test battery to ascertain relationships between reading ability and sensitivity to dynamic visual and auditory stimuli. The first analysis examined whether sensitivity to visual coherent motion and auditory frequency resolution differed between groups of children with different literacy and cognitive skills. For both tasks, a main effect of literacy group was found in the absence of a main effect for intelligence or an interaction between these factors. To assess the potential confounding effects of attention, a second analysis of the frequency discrimination data was conducted with performance on catch trials entered as a covariate. Significant effects for both the covariate and literacy skill was found, but again there was no main effect of intelligence, nor was there an interaction between intelligence and literacy skill. Regression analyses were conducted to determine the magnitude of the relationship between sensory and literacy skills in the entire sample. Both visual motion sensitivity and auditory sensitivity to frequency differences were robust predictors of children’s literacy skills and their orthographic and phonological skills.

The incidence and nature of letter orientation errors in reading disability.
Terepocki M, Kruk RS, Willows DM. J Learn Disabil 2002, 35(3):214-233.
Letter orientation confusions (reversals) in the reading and writing of 10-year-old children with and without reading disability were investigated to determine whether reading disability is associated with letter orientation errors and to identify the nature of the errors. In a variety of tasks measuring letter orientation confusions in reception (reversal detection and recognition) and production (controlled writing, copying), individuals with reading disability made more orientation confusions than average readers. Orientation errors were more frequent for reversible than for nonreversible items in tasks involving long-term memory processes. The results did not appear to be related to group differences in attention or speed of motor responding. Possible sources of orientation confusions, including deficient magnocellular system processing, mislabeling, and overreliance on visual strategies, are discussed.


Oculomotor abnormalities in attention deficit hyperactivity disorder. A preliminary study.
Mostofsky SH, Lasker AG, Cutting LE, Denckla MB, Zee DS. Neurology 2001, 57:423-430.
Background: Prevailing hypotheses suggest that attention deficit hyperactivity disorder (ADHD) is secondary to dysfunction of motor intentional systems mediated by prefrontal circuitry. Oculomotor paradigms provide a mechanism for examining and localizing dysfunction at the interface between movement and cognition.
Objective: Three different saccade tasks (reflexive or prosaccades, antisaccades, and memory-guided saccades) were used to examine functions necessary for the planning and the execution of eye movements, including motor response preparation, response inhibition, and working memory.
Methods: The study included 19 children with ADHD, divided into two groups: a group of 8 children on methylphenidate at the time of testing and a group of 11 children not taking any psychoactive medication. Results from the two groups were compared with those from 25 age- and gender-matched normal control children.
Results: Both groups of children with ADHD made significantly more directional errors than did controls on the antisaccade task and significantly more anticipatory errors than did controls on the memory-guided saccade task, findings that are consistent with deficits in response inhibition. There were no significant differences in prosaccade latency, although unmedicated children with ADHD showed significantly greater variability in latency on the prosaccade task than did controls. On the memory-guided saccade task there were no significant differences in saccade accuracy; however, unmedicated children with ADHD showed longer saccade latency than did either controls or medicated children with ADHD.
Conclusion: Oculomotor findings suggest that deficits in prefrontal functions, in particular response inhibition, contribute to behavioral abnormalities observed in ADHD. Findings also suggest that the administration of methylphenidate is associated with improvements in the consistency of motor response. Although there were no observed improvements in response inhibition with methylphenidate, conclusions await a design in which subjects complete testing both on and off medication.

Voluntary saccadic control in dyslexia.
Biscaldi M, Fischer B, Hartnegg K. Perception 2000, 29:509-521.
The role of eye-movement control in dyslexia is still unclear. Recent studies, however, confirmed that dyslexics show poor saccadic control in single and sequential target tasks. In the present study we investigated whether dyslexic subjects are impaired on an antisaccade task requiring saccades against the direction of a stimulus. Altogether, 620 subjects between the ages of 7 and 17 years were classified as dyslexics (N = 506) or control subjects (N = 114) on the grounds of the discrepancy between their intellectual abilities and reading/spelling achievements. All subjects performed an overlap prosaccade and a gap antisaccade task with 100 trials to each side of stimulation in random order. Variables analysed were the overall saccadic reaction time of both tasks; and from the antisaccade task the number of errors (prosaccades), the number of corrected errors, and the number of trials in which the subjects still failed to reach the side opposite the stimulus even after two saccades. An analysis of variance was carried out taking into account the development of saccadic behaviour with age and the differences between the groups. The results confirm development of saccade control with age, especially in the voluntary component (a frontal-lobe function) for both groups, but indicate that the antisaccade task performance, as measured by the error and the correction rate, is significantly worse in the dyslexic group at ages above 8 years. Up to 50% of the dyslexics performed the antisaccade task 1.5 standard deviations below the mean of the controls.


Smooth pursuit eye movements are associated with phonological awareness in preschool children.
Callu D, Giannopulu I, Escolano S, Cusin F, Jacquier-Roux M, Dellatolas G. Brain and Cognition 2000, 58:217-225.
Phonological awareness is strongly related to reading ability, but reports are more conflicting concerning the association of high level oculomotor skills with reading. Here, we show that phonological awareness is specifically associated with the ability to perform smooth pursuit eye movements in preschool children. Two large independent samples of preschool children (n=838 and n=732) aged 5-6.4 years, without history of neurological disorder, were examined by school medical doctors for visual and oculomotor problems. Nineteen percent of the children in the first sample and 14% in the second failed at the clinical evaluation of smooth pursuit eye movements, and 17 and 15%, respectively, presented another visual or oculomotor problem. Ten short cognitive tests were performed by the same children. Visual and oculomotor problems other than a failure on smooth pursuit were not consistently related to the cognitive tasks, with one exception, the visual recognition of letters. Children who failed at smooth pursuit obtained lower scores at a number of cognitive tasks, and especially phonological awareness tasks and copy of visually presented trajectories. Poor working memory and/or failure of anticipation during the tracking of a visual or auditory stimulus related to frontal cortex immaturity may explain these associations in preschool children.

Relationship between visual motor integration skill and academic performance in kindergarten through third grade.
Taylor Kulp M, Schmidt P. Optometry and Vision Science 1999, 76(3): 159-163.
Purpose: The objective of this study was to examine the relationship between visual motor integration skill and academic performance in kindergarten through third grade.
Methods: One hundred ninety-one (N = 191) children in kindergarten through third grade (mean age = 7.78 years; 52% male) from an upper-middle class, suburban, primarily Caucasian, elementary school near Cleveland, Ohio were included in this investigation. Visual analysis and visual motor integration skill were assessed with the Beery Developmental Test of Visual Motor Integration (VMI) long form because it is a commonly used test in both optometric and educational practice and has a detailed scoring system. The relationship between performance on the VMI and teachers’ ratings of academic achievement was analyzed because teachers’ grades are a primary means of assessing school performance. The children’s regular classroom teachers rated the children with respect to reading, math, and writing ability. Second and third grade children (N = 98) were also rated on spelling ability. Only experienced teachers were included in the investigation and the validity of the teachers’ ratings was substantiated by significant correlations with standardized test scores. Teachers were masked to performance on the VMI until the rating was completed. The Stanford Diagnostic Reading test, 4th edition, was also used as a measure of reading ability in the first graders and the Otis-Lennon School Ability test (OLSAT), 6th edition, was also used as a measure of school-related cognitive ability in the second graders.
Results: Performance on the VMI was found to be significantly related to teachers’ ratings of the children’s reading (p = 0.0001), math (p = 0.0001), writing (p = 0.0001) and spelling (p = 0.0118) ability. An analysis by age group revealed that performance on the VMI was significantly correlated with reading achievement ratings in the 7- and 8- year-olds (p<0.001 and p = 0.002, respectively), with math and writing achievement ratings in the 7-, 8-, and 9-year-olds (math: p<0.001, p = 0.004, and p = 0.003, respectively; writing: p<0.001, p = 0.008, and p = 0.016, respectively), and with spelling achievement ratings in the 8- and 9-year-olds (p = 0.040 and p = 0.007, respectively). VMI scores were also significantly related to performance on the Stanford Reading test in the first graders (p = 0.003) and to performance on the OLSAT in the second graders (verbal score: p = 0.005, nonverbal score: p = 0.002, and total score: p<0.001). In order to partially control for mathematical ability, an additional analysis was performed with children who were identified by the OLSAT as having either below average, average, or above average verbal reasoning scores ability (the verbal reasoning score consists of aural and arithmetic reasoning). This analysis again revealed a significant correlation between the VMI and teachers’ achievement ratings in math (p = 0.007 among second grade students with average ability). Finally, in order to partially control for cognitive ability related to writing, an additional analysis was performed with children who were identified by the OLSAT as having either below average, average, or above average nonverbal cluster OLSAT scores. (The nonverbal cluster consists of pictorial and figural reasoning.) This analysis again revealed a significant correlation between the VMI and teachers’ achievement ratings in writing (p = 0.001 among average second grade students).
Conclusion: Performance on a visual analysis and visual motor integration task is significantly related to academic performance in 7-, 8- and 9-year-olds.


Magnocellular visual function and children’s single word reading.
Cornelissen PL, Hansen PC, Hutton JL, Evangelinou V, Stein JF. Vision Res. 1998, 38(3):471-82.
Recent research has shown that reading disabled children find it unusually difficult to detect flickering or moving visual stimuli, consistent with impaired processing in the magnocellular visual stream. Yet, it remains controversial to suggest that reduced visual sensitivity of this kind might affect children’s reading. Here we suggest that when children read, impaired magnocellular function may degrade information about where letters are positioned with respect to each other, leading to reading errors which contain sounds not represented in the printed word. We call these orthographically inconsistent nonsense errors “letter” errors. To test this idea we assessed magnocellular function in a sample of 58 unselected children by using a coherent motion detection task. We then gave these children a single word reading task and found that their “letter” errors were best explained by independent contributions from motion detection (i.e., magnocellular function) and phonological awareness (assessed by a spoonerism task). This result held even when chronological age, reading ability, and IQ were controlled for. These findings suggest that impaired magnocellular visual function, as well as phonological deficits may affect how children read.


Effect of oculomotor and other visual skills on reading performance: A literature review.
Taylor Kulp M, Schmidt P. Optometry and Vision Science 1996, 73 (4): 283-292.
Reading disability is a multifaceted problem, which requires an interdisciplinary approach. Many visual difficulties have been shown to be related to reading ability. Efficient reading requires accurate eye movements and continuous integration of the information obtained from each fixation by the brain. A relation between oculomotor efficiency and reading skill has been shown in the literature. Frequently, these visual difficulties can be treated successfully with vision therapy.


The Vision Screening of Academically & Behaviorally At-Risk Pupils
Johnson R, Nottingham D, Stratton R, Zaba J. Journal of Behavioral Optometry 1996, 7(2):39.
The New York State Optometric Association Vision Screening Battery (NYSOA) was administered to 81 at-risk elementary, middle school, and high school students in order to rule out vision difficulties as contributing to academic difficulties and/or as to various determinations of attention deficit disorder (ADD), attention deficit hyperactivity disorder (ADHD), dyslexia or dyslexic, or oppositional-defiant behavior, etc. Thirty-three were classified as both academically and behaviorally at-risk. Ninety-seven percent of the students with behavioral problems failed at least one of the NYSOA subtests. A chi-square statistical analysis revealed that students who were academically at risk or behaviorally at risk scored significantly lower on the tracking, stereopsis, hyperopia, and color vision subtests. The results of this screening were also compared to several measures of academic achievement and subjective visual and academic assessment questionnaires.


Verbal and visual problems in reading disability.
Eden G, Stein J, Wood M, Wood F. Journal of Learning Disabilities 1995, 28 (5): 272-290.
In a preliminary study (Eden, Stein & Wood 1993), we showed that visuospatial and oculomotor tests can be used to differentiate children with reading disabilities from nondisabled children. In the present study, we investigated a larger sample of children to see if these findings held true. Using 93 children from the Bowman Gray Learning Disability Project (mean age = 11.3 years: 54 boys, 39 girls), we compared the phonological and visuospatial abilities of nondisabled children (children whose reading at fifth grade rated a Woodcock-Johnson reading standardized score between 85 and 115), and children with reading disability (whose reading standardized score was below 85 on the Woodcock-Johnson). In addition to performing poorly on verbal tests, the children with reading disability were significantly worse than nondisabled children at many visual and eye movement tasks. A high proportion of the variance (68%) in reading ability of both the nondisabled children and those with reading disability could be predicted 3 by combining visual and phonological scores in a multiple regression. These results provide further support for the hypothesis that reading disability may, to some extent, result from dysfunction of the visual and oculomotor systems.


Differences in eye movements and reading problems in dyslexic and normal children.
Eden G, Stein JF, Wood HM, Wood FB. Vision Research 1994, 34 (10): 1345-1358.
It has been suggested that eye movement abnormalities seen in dyslexics are attributable to their language problems. In order to investigate this claim, we studied eye movements in dyslexic children during several non-reading tasks. Dyslexic children were compared to normal and backward readers on measures of fixation, vergence amplitude, saccade and smooth pursuit. The results were compared to the children’s phonological ability. Dyslexic children (n = 26) had significantly worse eye movement stability during fixation of small targets than normal children (n = 30). Vergence amplitudes were lower for dyslexics than for controls. A qualitative assessment of saccadic eye movements revealed that dyslexics exhibit fixation instability at the end of saccades. Assessment of smooth pursuit revealed poor smooth pursuit in the dyslexic group, particularly when pursuing a target moving from left to right. Dyslexic children also performed significantly worse than normal children on a test of phonological awareness (Pig Latin). Eye movement results were studied in the light of the findings on phonological awareness: dyslexics with small vergence amplitudes also always have poor phonemic awareness. However, poor fixation control is found in dyslexics with or without poor phonological ability. The backward reading children performed similar to the dyslexics on all tests, suggesting that the deficiencies observed in this study are not specific to children with dyslexia. The problems experienced by the children (revealed by a questionnaire) are in agreement with those measured in terms of eye movement recording sand phonemic awareness. Sex, handedness, IQ or the presence of attention deficit disorder (ADD) did not appear to influence the children’s performances on any of the eye movement tasks. The presence of oculomotor abnormalities in a nonreading task strongly suggest that the underlying deficit in the control of eye movements seen in dyslexics is not caused by language problems alone.


Visuo-spatial discrimination and mirror image letter reversals in reading.
McMonnies CW. J Am Optom Assoc 1992, 63(10):698-704.
This review compares visuo-spatial and linguistic mechanisms for discriminating between mirror image letters. The conclusion is drawn that both processes play a role in efficient reading, their relative contributions varying with reading experience and ability. It is shown that arguments used to reject visuo-spatial theories in mirror image letter reversals are flawed. Attention is drawn to the importance of visuo-spatial discrimination of mirror image letters, based on confident left/right body awareness, for beginning readers and for older children who are deficient in compensatory linguistic skills. When confused left/right body awareness is found in association with reversal problems, there is an indication to provide remediatio
n that includes the promotion of mirror image letter discrimination based on confident left/right body awareness. Early intervention (pre-school and infants class) programs that teach left/right body awareness as a pre-reading skill are justified when the progress of beginning readers is facilitated and the need for remedial intervention is reduced in later years.


Jordan Left-Right Reversal Test: An analysis of visual reversals in children and significance for reading problems.
Jordan BT, Jordan SG. Child Psychiatry Hum Dev. 1990, 21(1):65-73.
The Jordan Left-Right Reversal Test (JLRRT) was first published in 1974 (1) as a convenient measure of symbol reversals in children. A current revision of the test, based on 3,000 children, showed error scores to be inversely related to age and sex.


Learning disabled children and a group of below average readers made significantly more errors, indicating that visual reversals are dysfunctional for reading skills.

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