By Alessandro Toschino, Optician and Optometrist
and student of the Master in Clinical Optometry and Vision Therapy
This study aims, through a review of the literature, to consider the main components of a protocol of an eye and vision examination for school-age children with dyslexia or reading problems. A comparison was made between the guideline proposed by the American Optometric Association (AOA) and other studies in which the optometric values significant in the evaluation of this category of children were sought. These are the accommodation amplitude, the accommodation facility and fusional vergence ranges. In addition, the importance of an evaluation of aspects that link vision to learning was stressed: the assessment of visual information processing skills acquires crucial importance for children with dyslexia or reading problems. A new approach to the problem is proposed, expanding the field of research of the optometrist and recommending a multidisciplinary work for a correct and complete visual examination for these children.
Key words: Optometry, Protocol, Vision examination, School-age children, Dyslexic children
Eyes represent the window to the world, so their health and good functioning are elements not to understimate. It is important to understand that in every age of our life, the eyes are not the same of the previous examination and they will change before the next one. Specially in the first age of our life the eyes, as other parts of our body, are in evolution and medical evaluation is crucial in order to avoid disorders that can lead to problems during the child’s normal development. From the point of view of optometry, it is important to distinguish between child and adult evaluation: due to different age, development, interests, comprehension and participation, the conduction of the examination and the tests used could not be the same and with the same results.
For this reason, the American Optometric Association (AOA) published in 2017 the Evidence-Based Practice Guideline for the Comprehensive Paediatric Eye and Vision Examination that describes procedures for evaluation for the eye health and vision status of infants and children.
The objectives of this Guideline are:
– Recommend an optimal timetable from newborn to 18 years old of age
– Suggest appropriate procedures of eye and vision examination
– Reduce the risks and adverse effects of eye and vision problems
– Inform and educate about the importance of prevention
The choice of this guideline was made because this is one of the most recent and complete documents in which it is analyzed the field of paediatric eye and vision examination.
In the guideline it is made an important differentiation from different ages of children:
– Infants and toodlers (newborn to 2 years of age)
– Preschool children (3 years to 5 years of age)
– School-age children (6 to 18 years of age)
This distinction is important because even if there arefew years of differencebetween these groups, there are different child’s developmental ages and specific capabilities. For this reason, in the AOA guideline there are explained different examination procedures for the three categories. But in general terms, the goals of the comprehensive eye and vision examination are:
– Evaluation of refractive, binocular and accommodative status
– Evaluation of ocular health
– Treatment and management plan
– Recommendations for prevention, treatment, management and future care
Focusing on the category of school-age children, in which the examination is more similar to the adult one, the guideline suggests these potential components of the comprehensive eye and vision examination:
– Patient history: nature and history of the presenting problem, visual and ocular history, general health history, medication reconciliation, family eye and medical histories, developmental history, school performance history, daily activities
– Visual acuity: Snellen or ETDRS
– Refraction: static retinoscopy, autorefraction, eventual cycloplegic retinoscopy, sujective refraction
– Binocular vision, ocular motility and accommodation: ocular alignment assessment at distance and at near vision (cover test, Hirschberg test, Krimsky test, Von Graefe phoria, Modified Thorington, Maddox Rod); ocular motility assessment (fixation, saccades, smooth pursuit); near point of convergence; stereopsis; positive and negative fusional vergence ranges; accommodation (amplitude, facility, response, positive and negative relative accommodation)
– Color vision testing
– Ocular and systemic health assessment: pupillary response, visual field, ocular anterior segment and adnexa, ocular posterior segment, intraocular pressure
– Supplement testing: electrodiagnostic testing; imaging (ultrasonography, optical coherence topography, scanning laser ophtalmoscopy, fundus photography, corneal topography, computerized tomography, Scheimpflug camera for anterior segment tomography); testing for learning-related vision problems (more extensive accommodation testing, binocular vision, eye movements, assessment of visual information processing skills)
This last part about supplementing testing and in particular those concerning learning-related vision problems can be an important subject of interest for a study in order to define what could be the possible good eye and vision examination for the school-age children that present these problems.
Among different learning-related vision problems, it is important to underline the reading problems and in particular dyslexia.
Dyslexia is a reading disability characterized by difficulties with decoding, fluent word recognition, reading-comprehension skills, impairment in spelling and writing. Maybe we can deal with poor readers, that are anyone not reading as well as other children of the same age, but other aspects of their education are not affected; among these children there may be dyslexic ones or not.
In this study, we will focus on a specific category of children with learning-related problems: children with reading problems (dyslexic and poor readers). We will analyze some different studies in which there is the optometric evaluation of school-age children with problems concerning reading. The goal is to understand what could be the aspects on which to focus more in an eye and vision examination for a correct assessment in children with reading problems.
In this literature review there was made a research of some studies about the results of eye and vision examination in children with dyslexia or poor readers. Through the comparison of these results with ones from control groups of normal readers, there was made a reflection about what could be the most important optometric tests useful for a comprehensive eye and vision examination of dyslexic children, in comparison also with the indications of the AOA guideline.
There were also analyzed some researches about the link between learning disabilities, dyslexia and vision in order to understand the importance of the eye and vision examination in the evaluation of dyslexia.
The source from which to obtain the studies has been the database Pubmed. There were used some key words for research such as “optometry”, “children”, “reading test”, “dyslexia”, “vision”.
There were used inclusion and exclusion criteria regarding the type of studies reviewed: there were chosen articles in which there were tested school-age children (from 6 to 14 years) with reading problems (dyslexia or poor readers). This selection is attributable to the fact that in the age of entry into school and therefore with the first interactions with reading and writing, it may be important an assessment made by optometrist so that a problem can be found in this type of activity useful for the development of the child.
In the study of Eden, Stein, Wood and Wood (1994) there were evaluated 93 children with age between 10.2 and 12.6 years. Of these, 39 were normal readers, 26 reading disabled, 12 backward readers and 16 miscellaneous readers. The assessment for each child included intellectual quotient(IQ), reading skills (word identification, comprehension), eye movements, phonological test, questionnaire about symptoms of reading problems and standard eye examination. The results show that dyslexic children have reduced fixation stability and vergence amplitude, fixation instability at the end of saccades, poor smooth pursuit, particularly from distance to near vision and reduced phonological awareness. In addiction, backward readers have similar results: so these deficiencies are not specific to dyslexics. An important statement is also that deficits in the control of eye movements are not caused by language problems alone.
Feizabadi, Jafarzadehpur and Akrami (2018) studied the near point of convergence (NPC), the near point of accommodation (NPA) and the stereoacuity in 27 dyslexic children compared to 40 control children (age, sex, social class-matched) with an age between 7 and 13 years old. The first two data were tested with the push-up method, while the stereoacuity was tested with Titmus stereotest. The results demonstrated that monocular and binocular NPA in dyslexics are reduced towards monocular and binocular NPA in non-dyslexic children; instead, there were no differencies in NPC and stereopsis between the two groups.
Palomo-Alvarez and Puell have performed three different studies in which they have estimated some elements related to reading in poor readers children without dyslexia. In a first study, Palomo-Alvarez and Puell (2009), did an optometric exam and in particular an assessment of oculomotor scanning and reading in 81 poor readers without dyslexia with ages between 8 and 11 years. In the examination there were evaluated: accommodative function, binocular vision, perception and reading abilities, and particular attention has been given to the Developmental Eye Movement (DEM) test. The results refer to the DEM test indeed: there was found that in poor readers the horizontal time is less than the one of normal readers. For this reason, also reading speed is reduced.
In the second study, Palomo-Alvarez and Puell (2010),87 poor readers children without dyslexia were compared with 32 control group (age-matched normal readers children) with age from 8 to 13 years. In the eye and vision examinations for the two groups, some elements were studied: distance and near horizontal heterophoria (with Von Graefe), distance and near horizontal fusional vergence ranges (with Risley prisms), AC/A ratio (gradient method), NPC (push-up method) and stereoacuity (with Randot stereotest).Results demonstrated that in poor readersthe values of distance base in (BI) ranges were reduced with respect of the normal readers; but distance base out (BO) ranges, distance and near horizontal heterophoria, near horizontal fusional vergence, AC/A ratio, NPC and stereoacuity present no differencies between the two groups.
In the third study, Palomo-Alvarez and Puell (2008), did a study similar to the precedent comparing87 poor readers children without dyslexia with 32 control group (age-matched normal readers children), with age from 8 to 13 years. The eye and vision examination were conducted focusing more on accommodation: in fact, there were studied positive relative accommodation (PRA) and negative relative accommodation(NRA), monocular accommodative amplitude (with minus lens method) and accommodative facility (with ± 2,00D flipper). Results showed that in poor readers the values of monocular accommodative amplitude (AA) and binocular accommodative facility were reduced with respect of to normal readers; instead, for values of NRA and PRA there were no differencies between the two groups of children.
Wahlberg-Ramsay, Nordstrom, Salkic and Brautaset (2012), analyzed in their study 63 dyslexic children and compared them to a control group of 60 children (age-matched normal reader children), with age from 10 to 16. The assessment included visual acuity (VA), refraction, near point of convergence (with push-up), monocular and binocular accommodative amplitude (AA), stereoacuity (with Random dot stereotest), heterophoria and heterotropia. From the data it can be assumed that in dyslexics monocular and binocular AA were reduced, while monocular and binocular VA, refractive error, NPC, stereopsis, phorias, fusional reserves present no differences between dyslexic and normal readers. It could be also said that binocular deficits in dyslexic children are probably a result of phonological deficit.
Niechwieij-Szwedo, Alramis and Christian (2017) focused on 19 children with identified reading problems and 19 for the control group (age-matched normal readers children) of age between 5.58 and 11.92 years. There were made an assessment of visual acuity, stereoacuity (with Random stereotest), horizontal fusional reserves (with prism bars), monocular and binocular accommodative facility (with ± 2,00D flipper), accommodative amplitude (with push-up method), and also an assessment of fine motor skills with two practical tests: bead-threading task (10 beads placed on a blunt, vertically-mounted needle) and peg-board task (9 pegs placed on a custom-made wooden board). Tests showed that in the case of children with reading difficulties bead-threading was significantly worse. It is important to remember that accommodative facility is significantly associated with motor performance.
Christian, Nandakumar, Hrynchak and Irving (2018) have analyzed 121 children identified with reading problems with age from 6 to 14 years. They have paid attention to different elements of eye and vision examination: visual acuity, distance and near heterophoria and heterotropia (with cover test and Hirschberg test), saccades, ocular motility (with Broad-H test), stereoacuity (with Randot stereotest), accommodative amplitude, near point of convergence (with push-up method), monocular and binocular accommodative facility (with ± 2,00D flipper), accommodative response (MEM), static retinoscopy, distance and near fusional vergence ranges (with prism bars). The following results could be the most relevant from this study:
– 68% had NPC <5cm
– 50% had normal fusional vergence ranges, but 46% abnormal base out (BO) break
– 91% had normal binocular facility
– 70% had normal accommodative amplitude.
From these, it has been thought that NPC, accommodative facility, accommodative amplitude and fusional ranges could be the recommended tests for an assessment of children with a reading problem.
Making a comparison between the studies presented allows to evaluate which tests can be more important for a more accurate assessment of dyslexic children.In the following table (Table 1) there are reported the most valuable tests from every study.
Table 1. Most valuable tests of the studies
Most valuable tests
Eden, Stein, Wood and Wood (1994)
Ocular motility, distance and near horizontal fusional vergence ranges
Feizabadi, Jafarzadehpur and Akrami (2018)
Monocular and binocular near point of accommodation (NPA)
Palomo-Alvarez and Puell (2009)
DEM test (in particular, horizontal time and reading speed)
Palomo-Alvarez and Puell (2010)
Distance horizontal base in (BI) vergence
Palomo-Alvarez and Puell (2008)
Monocular accommodative amplitude (AA) and binocular accommodative facility
Wahlberg-Ramsay, Nordstrom, Salkic and Brautaset (2012)
Monocular and binocular accommodative amplitude (AA)
Niechwieij-Szwedo, Alramis and Christian (2017)
Bead-threading task (fine motor skill), accommodative facility
Christian, Nandakumar, Hrynchak and Irving (2018)
Near point of convergence (NPC), accommodative facility, accommodative amplitude, fusional ranges
From the guideline of AOA, the components of the right eye and vision examination for school-age children represents general tests to do for every children of these age and not an specific case of dyslexia or reading problems. Only in the part of “supplement testing” there were mentioned tests to be submitted in case of children with learning-related vision problems such as dyslexia. These tests are a more extensive assessment of accommodation, binocular vision, eye movements, and visual information processing skills.
Instead, as reported in Table 1, in the studies used for the review there were an indication about what are the optometric values that present a difference between children with reading problems and normal readers. These optometric values are: ocular motility, fusional vergence ranges, monocular and binocular NPA, DEM test, accommodative amplitude, accommodative facility, fine motor skills and NPC.
Among these, the most frequent are fusional vergence ranges, accommodative amplitude and accommodative facility.
In the literature, there are not a lot of studies that define the relation between dyslexia and vision. And in this scarcity of sources there is also much controversy about this link and the cause-effect relationship that there can be between these two elements.
For instance, Beauchamp (1987) states that there is the same incidence of ocular abnormalities between dyslexic and normal people, and also that there is no evidence of improving by visual training, use of glasses or neurologic organizational training. He argues also that dyslexia and related disabilities maybe are linked to genetic, biochemical and/or structural brain changes.
Wright (2007) says that dyslexia is a difficulty in reading with impairment in spelling and writing. He affirms that dyslexic people have different eye movements and deficits in visual processing within the cortical and extra-striate visual systems; but these elements are not causal factors of the defect, but only corollary ones.
The Committee on Children With Disabilities American Academy of Pediatrics (AAP) and American Academy of Ophthalmology (AAO), American Association for Pediatric Ophthalmology and Strabismus (AAPOS) (1998) say that learning disabilities have multifactorial etiology and also there are no evidence that correction of visual defects alter the brain’s processing; so there is no relation between vision and dyslexia.
But the study of Bowan (2002) is in contrast to the precedent study because the authors ignored relevant literature that argues a relation between vision and academic performance and not a single organization within the optometry field believes vision is the only responsible for dyslexia and learning disabilities. It also states that there is a deficit in oculomotor abilities in reading disabled/dyslexic students.
Handler, Firson from the Section on Ophthalmology and Council on Children with Disabilities, American Academy of Ophthalmology, American Association for Pediatric Ophthalmology and Strabismus, American Association of Certified Orthoptists (2011) report on the reading disability or dyslexia:
– It is a receptive language-based difficulty in decoding, fluent word recognition, reading comprehension skills
– It is a deficit in the phonologic component of language
– Vision problems can interfere in it, but they are not the cause: in fact, children wth or without it have the same visual function and ocular health
– It is probably caused by neurologic differences in brain structure and function: storage, process and communication of information are affected
Some studies found an important correlation between dyslexia and visual processing.
Ygge and Lennerstrand (1997) argue that dyslexia is caused by visual processing abnormalities: magnocellular visual pathway abnormality and deficit in contrast sensitivity of transient system.
Vidyasagar and Pammer (2009) claim that dyslexia refers to poor inputs in the regions mediating grapheme-phoneme correspondance and, in general, to every temporal provcessing deficit. And from this derives an impairment in phonemic awareness.
Despite these controversies in the theoretical relationship between dyslexia and vision, some studies seek a more practical correlation and are based on optometric tests.
Because the goal of this work is to understand what the guideline of a visual examination for the evaluation of school-age children with dyslexia may be, we can affirm that the most significant element of the above mentioned studies is the fact that dyslexia is linked to a problem in visual information processing.
This reflects the indications of the AOA guideline, in which we remind that among the supplement testing is mentioned the evaluation of visual information processing skills.
Even if in the studies mentioned in this review there were not a defined procedure to use in the assessment of school-age children with dyslexia or reading-problems in general, there were some indications about what can be the areas of vision evaluation in which the results could change in the presence of reading problems compared with normal readers. From this point of view, we could be able to advise on the main tests of visual examination on which to focus attention in case we are faced with a child with reading problems.
So, it might be right to maintain the structure of the visual examination proposed by the guideline focusing, in the case of a dyslexic child, on those visual areas and those tests reported in the studies examined that could give significant results for a proper assessment.
As reported previously, evaluation of accommodation and binocular vision are very important for every examination and in particular for dyslexic children.
About the evaluation of accommodation, the most important tests to be administered are:
– Amplitude of accommodation: monocular and binocular, with the push-up method, expected value from the Hofstetter’s formula (AA = 15 – ¼*age); normally, values are reduced in dyslexic children
– Accommodation facility: monocular and binocular, with ± 2,00D flipper, expected values in Table 2, reliability since 7 years old; normally, values are reduced in dyslexic children
Table 2. Expected values of accommodative facility
5.5 ± 2.5
3 ± 2.5
6.5 ± 2.5
3.5 ± 2.5
7 ± 2.5
5 ± 2.5
About the evaluation of binocular vision, the most important test to be administered is:
– Fusional vergence ranges: with prism bars or loose prisms, expected values in Table 3, no indication of blur because it is difficult to explain to the child and understand by him or her; normally, values are reduced in dyslexic children.
Table 3. Expected values of fusional vergence ranges
BO, positive fusional vergence (cm)
BI, negative fusional vergence (cm)
These tests are the ones to focus on when we are in presence of a dyslexic child, according to the studies analysed in the review.
Surely, the assessment of oculomotricity is also important because particularly saccades and fixation are movements very used during the reading.
Pavlidis (1985) says that in dyslexics there are erratic movements: excessive number of regressions and fixations, primarily due to brain malfunctions. These results, along with those of Palomo-Alvarez and Puell (2009) about DEM test and Eden, Stein, Wood and Wood (1994)about eye movements in general, suggest that the assessment of this area of vision is crucial in an eye and vision examination for school-age children with dyslexia.
It is important to remember that throughout visual examination, if children haveproblems in recognizing the grapheme-phoneme relationship being dyslexic, it is necessary to use in all those tests where reading is required, such as visual acuity, or refraction, or the accommodative amplitude, eye charts with signs or images, to prevent the child from finding himself in difficulty and unable to complete the task.
At the end of this debate about the optometric tests used in the eye and vision examination for dyslexic children, it is important to fix the main features of the optometrist’s approach to the exam for children with reading problems. In fact, the latter no longer consists of a series of tests that assess only the functionality of the visual system, but there are added multidisciplinary assessments related to the perceptual and cognitive aspect of vision.
The College of Optometrists in Vision Development, the American Optometric Association, the American Academy of Optometry (1997) state that the areas of visual function are:
– visual integrity (eye health, refractive status)
– visual efficiency (accommodation, binocular vision, eye movements)
– visual information processing (identification and discrimination, spatial awareness, memory, integration with other senses)
So the eye and visual examination, principally for dyslexic children, should evaluate all these three areas for a comprehensive analysis of the visual function.
Wesson (1993) propose a model for the identification and management of reading problems in the primary care optometry. Further the optometric assessment, there are useful having a visual motor skills and spatial analysis, an auditory skills analysis, a visual motor (short term) memory recall, with specific intelligence and dyslexic testing. We cannot specify tests for these analysis because they are outside the scope of this study.
Surely, the importance of visual information processingis of high profile in the evaluation of dyslexic children. Through assessment of visual discrimination and shape recognition, visual memory, figure-shape perception and visuo-motor integration, we could understand how the child analyzes and interprets what he sees. The evaluation of other specialists not related to the eye and vision could help the optometristto reach a more complete evaluation regarding visual-auditory integration, the relationship with the mouth and speech, the postural evaluation that involves the whole body. Figures such as psychologists, osteopaths, physiotherapists, audiometricians, orthodontists, speech therapistsshould work side by side with optometrists to evaluate children with dyslexia and reading problems.
We can say the guideline of comprehensive eye and vision examination of the AOA give us a complete protocol useful to assess school-age children with dyslexia or reading problems.The indications that we find regarding supplement testing aimed precisely at learning disorders, namely in-depth analysis of tests for accommodation, binocular vision, eye movements and visual information processing skills, already provide an excellent basis for our purpose. Certainly, in such a generic guide, it was not possible to analyze which tests have more relevance among those included in the areas of vision just mentioned. From the other studies analyzed we were therefore able to define the importance of optometric values such as accommodative amplitude, accommodative facility, fusional vergence ranges, fixation and saccades.At the beginning of the examination, it is advisable to have a complete case history of the academic path and an analysis of the child’s work, documents and testimonials from teachers and those who accompany him in the school and any reports of other professionals, as well as information on symptoms and signs.Also, the visual information processing skills play a fundamental role in the evaluation of this kind of children, but it goes beyond what is the basic preparation of an optometrist and it is therefore necessary to deepen the knowledge of the latter and the support of other professionals such as psychologists, osteopaths, physiotherapists, audiometricians, orthodontists, speech therapists. Despite all this, as Leslie (2004) also states, the role of the optometrist towards those who have problems in reading is precisely that of offering a competent examination and subsequent aids to solve the impediment, referring to others for more specialised optometric investigation.
It is difficult to create a unique protocol that could be useful in every case and for every children because every case is different from each other. However, it is important to give guidelines to follow in the face of cases of this type, and this is the case of the AOA guideline which is already complete. With some more elements derived from this work surely it could be reached a common line that all optometrists attentive to these types of cases can take as a reference for their daily work and for the health of children. Other subsequent studies will certainly have to be carried out to expand the field of research with a number of studies even greater than those used here.
American Optometric Association (AOA) Evidence-Based Optometry Guideline Development Group (2017). Comprehensive Pediatric Eye and Vision Examination.
Beauchamp, G. R. (1987). Background Information: Learning Disabilities, Dyslexia and Vision. Journal of Learning Disabilities, 20(7), 411-413.
Bowan, M. D. (2002). Learning disabilities, dyslexia, and vision: a subject review – A rebuttal, literature review, and commentary. Public Health, 73(9), 553-575.
Christian, L. W., Nandakumar, K., Hrynchak, P. K. and Irving, E. L. (2018). Visual and binocular status in elementary school children with reading problems. Journal of Optometry, 11, 160-166.
College of Optometrists in Vision Development, American Optometric Association, the American Academy of Optometry (1997). Vision, learning and dyslexia.
Committee on Children With Disabilities American Academy of Pediatrics (AAP), American Academy of Ophthalmology (AAO) and American Association for Pediatric Ophthalmology and Strabismus (AAPOS) (1998). Learning Disabilities, Dyslexia, and Vision: A Subject Review. Pediatrics, 102(5), 1217-1219.
Eden, G. F., Stein, J. F., Wood, H. M. and Wood, F. B. (1994). Differencies in Eye Movements and Reading Problems in Dyslexic and Normal Children. Vision Research, 34(10), 1345-1358.
Feizabadi, M., Jafarzadephur, E. and Akrami, M. (2018). Accommodation, convergence, and stereopsis in dyslexic schoolchilden. Middle East AfricanJournal of Ophtalmology, 25, 14-18.
Handler, S. M., Firson W. M., Section on Ophthalmology and Council on Children with Disabilities, American Academy of Ophthalmology, American Association for Pediatric Ophthalmology and Strabismus and American Association of Certified Orthoptists (2011), Joint Technical Report – Learning Disabilities, Dyslexia, and Vision. Pediatrics, 127(3), e818-e856.
Leslie, S. (2004). The optometrist’s role in learning difficulties and dyslexia. Clinical and Experimental Optometry, 87(1), 1-3
Niechwiej-Szwedo, E., Almaris, F. and Christian, L. W. (2017). Association between fine motor skills and binocular visual function in children with reading difficulties. Human Movement Science, 56, 1-10.
Palomo-Alvarez, C. and Puell, M. C. (2008). Accommodative function in school children with reading difficulties. Graefe’s Archive for Clinical and Experimental Ophtalmology, 246, 1769-1774.
Palomo-Alvarez, C. and Puell, M. C. (2009). Relationship between oculomotor scanning determined by the DEM test and a contextual reading test in schoolchildren with reading difficulties. Graefe’s Archive for Clinical and Experimental Ophtalmology, 247, 1243-1249.
Palomo-Alvarez, C. and Puell, M. C. (2010). Binocular function in school children with reading difficulties. Graefe’s Archive for Clinical and Experimental Ophtalmology, 248, 885-892.
Pavlidis, G. T. (1985). Eye Movements in Dyslexia: Their Diagnostic Significance. Journal of Learning Disabilities, 18(1), 42-50.
Vidyasagar, T. R. and Pammer, K. (2009). Dyslexia: a deficit in visuo-spatial attention, not in phonological processing. Trends in Cognitive Sciences, 14(2), 57-63.
Wahlberg-Ramsay, M., Nordstrom, M., Salkic, J. and Brautaset R. (2012). Evaluation of Aspects of Binocular Vision in Children With Dyslexia. Strabismus, 20(4), 139-144.
Wesson, M. D. (1993). Diagnosis and Management of Reading Dysfunction for the Primary Care Optometrist. Optometry and Vision Science, 357-368.
Wright, C. (2007). Learning disorders, dyslexia and vision. Australian Family Physician, 36(10), 843-845.
Ygge, J. and Lennerstrand, G. (1997). Visual impairment and dyslexia in childhood. Current Opinion in Ophtalmology, 8(5), 40-44.