Eye Exams and Eye Tests for Dyslexia
Binocular vision problems with eye teaming coordination and/or focusing often occur with or can be mistaken for dyslexia. These symptoms can be successfully treated with vision therapy eye exercises, so a comprehensive binocular eye exam is recommended before making the diagnosis of dyslexia or providing other treatments, such as colored lenses.
Optometric Assessment and
Management of Dyslexia
Frank Eperjesi BSc, PhD, MCOptom, FAAO
Dyslexia has been described as a language coding problem1 and can be considered to be synonymous with the term specific reading problem. It is not related
to social, emotional, economic or obvious disease (e.g. Down's syndrome) problems and can only be diagnosed by an educational or child psychologist. There may be a difficulty with reading, spelling, understanding Language that is heard, and clear expression when speaking or writing. Some sufferers may have
difficulty with speaking clearly or with handwriting. Others have difficulty with right and Left or the concept of before and after. Others may have less severe or even mild difficulty in one or two other areas such as organising. Some have additional problems such as attentional deficits. No two dyslexics are alike: each has individual strengths and weaknesses2.
An unexpected gap exists between the potential for learning and school achievement. i.e. their academic skills are 'out of step' with their general ability. It is important to remember that not all have problems with reading 3. It is a medical problem and is considered to be caused by a 'minimal brain dysfunction', also described as a differential brain function. Rosen et al4 noted that there can be one or more (up to fifty) affected sites or Lesions in the brain, in which small cortical areas have abnormally arranged cells.
Research has indicated that up to 15% of the population may be dyslexic and that fewer than one in ten will actually be identified as needing help and be able to receive formal diagnosis. A proportion will overcome early difficulties but for the majority learning difficulties are likely to persist and to have deleterious consequences on their later careers2.
People are born with dyslexia and often other members of the family are dyslexic or have a difficulty learning to read and spell. Dyslexia is not out grown, although most dyslexics develop coping strategies (e.g. avoiding reading). Dyslexics may have a wide range of talents, for example in art, drama, maths and sports, yet they may have difficulty remembering things or organising themselves2.
This article will concentrate on the optometric assessment and management of those who have dyslexia but the techniques described are equally valid for anyone who is under achieving at school or work whether they are formerly diagnosed as dyslexic or not.
Vision has been defined as a continuous and integrative process that can be divided into three components: (1) visual acuity, including refractive status; (2) visual efficiency, which is composed of oculomotor, accommodative and binocular vision skills; and (3) visual perceptual-motor skills, which represent the ability to recognise and discriminate visual stimuli and interpret them correctly in the light of previous experience3. While it is recognised that all of these components are equally important the emphasis will be placed on visual efficiency
Vision problems and dyslexia
A useful model has been put forward in an attempt to relate vision problems, dyslexia and other general problems1 (Figure 1). A general reading problem due mainly to vision problems, such as high, uncorrected hyperopic astigmatism would fall into circle 1. An individual with dyslexia and a concurrent vision problem would fall into area 4. From the diagram it can be seen that optometric evaluation would be useful for those people who fall into circle l and in particular areas indicated by and in particular areas indicated in Figure 1 by 4, 5 and 7.
Visual disorders such as hyperopia, convergence insufficiency, poor fusional vergence reserves, fixation disparity, hyperphoria, anisometropia, accommodative dysfunctions. among other dysfunctions have been shown to adversely affect reading performance and sustainability23.
This article will focus on the assessment of vergence and accommodative ability and the management of vergence and accommodative dysfunction. The assessment techniques and management strategies described below are not intended to be prescriptive or in any way describe a gold standard; there will be other tests and management lines that practitioners will use and consider better than those described here. The protocol described here was learnt and adopted by the author by combining experience obtained from the Specific Learning Difficulties Clinic at the Institute of Optometry, from general optometric practice and from information obtained from the literature (see below for a List of useful texts). Information on the assessment and management of saccadic and pursuit eye movements and fixation can be obtained from Griffin et al1.
Visual perceptual distortions and symptoms
Some children and adults, who have difficulty with reading, experience visual perceptual distortion and complain of asthenopic symptoms when viewing a page of print. The Letters may appear to move, jumble or to blur; white paper may glare and cause eyestrain or headaches. The resulting visual and physical discomfort is very likely to interfere with reading, and often attention and concentration are reduced. These distortions can be caused by a conventional optometric anomaly such as hyperopic astigmatism, a deficit in the binocular vision system (reduced visual efficiency), by Meares-Irlen Syndrome or a combination of some or all of these. Lightstone and Evans5 have suggested a sequential assessment and management plan to determine the cause of these signs and symptoms.
Visual perceptual distortions and asthenopic symptoms alleviated by individually prescribed coloured filters are considered to be due to Meares-Irlen Syndrome6. These distortions and symptoms can occur quite independently of any eye problem in people whose sight is otherwise perfect. Meares-Irlen Syndrome may be due to pattern glare, which has been described as an over sensitivity to the stripy line pattern that dark print makes on a white page7. This can occur in a person with or without dyslexia and probably does not cause dyslexia but can however, hinder educational rehabilitation. Some people with specific reading and learning difficulties may not voluntarily report experiencing these visual distortions and symptoms, and it is therefore important to remember that it may take detailed and sensitive questioning from an experienced practitioner to elicit these problems.
Binocular vision (visual efficiency) evaluation
The two main binocular vision related problems that occur are vergence and accommodative disorders. The vergence and accommodative mechanisms must be functioning efficiently to facilitate accurate sustained and reading. These two anomalies can occur together or independently and are amenable to treatment with lenses or eye exercises. These are varied and are chosen to match the individuals age and specific problem.
Vergence disorders are very common in non-presbyopic subjects and can result in ocular discomfort, headaches, diplopia, blurred vision and fatigue during reading and other near point tasks. Some subjects do not have asthenopia because they avoid near-point tasks.
There is now no doubt that vision problems and in particular binocular vision anomalies can seriously affect the ability to learn to read although it is also readily accepted that vision problems are not a direct cause of true dyslexia. ALL children and adults who are reading or learning underachievers, whether a formal diagnosis of dyslexia has been made or not, require a detailed evaluation of visual function, especially of the binocular vision system, at an early stage in their remediation.
- Griffin et al. (1997). Optometric Management of Reading Dysfunction. Butterworth-Heinemann, Newton.
- Prior, M. (1996). Understanding Specific Learning Difficulties. Psychology Press, Hove.
- Garzia, R. P. (1996) Vision and Reading. Mosby, St Louis.
- Rosen, G. D., Sherman, G. F.and Galaburda, A. M. (1993). Dyslexia and Brain Pathology: Experimental Animal Models in Dyslexia and Development: Neurological Aspects of Extraordinary Brains (ed.) A. M. Galaburda. Harvard College, Boston.
- Lightstone, A. and Evans, B. J.W. (1995). A new protocol for the optometric management of patients with reading difficulties. Ophthalmic and Physiological Optics. 15, 507-512.
- Evans, B. J. W., Wilkins, A. J., Brown, J., Busby, A., Wingfield, A. E., Jeanes, R., and Bald, J. (1994). A preliminary investigation into the aetiology of Meares-Irlen Syndrome. Ophthalmic and Physiological Optics. 14, 365-370.
- Wilkins, A. J (1995). Visual Stress. Oxford Science Publications, Oxford.
- Simons, H. D. and Grisham, J. D. (1987). Binocular anomalies and reading problems. Journal of the American Optometric Association. 58, 578-87.
- Evans, B. J. W. (1997). Pickwell's Binocular Vision Anomalies: Investigation and Treatment. Butterworth-Heinemann, Oxford.
- Evans, B. J. W, Drasdo, N, and Richards, I. L. (1994). Investigation of accommodative and binocular function in dyslexia. Ophthalmic and Physiological Optics. 1, 5-19.
- O'Grady, J. (1984). The relationship between vision and educational performance: a study of year 2 children in Tasmania. Australian Journal of Optometry. 64, 126-40.
- Griffin, J. R. and Gn'sham, J. D. (1995) Binocular Anomalies: Diagnosis and Vision Therapy (3rd ed). Butterworth-Heinemann. Boston.
- Mallett, R. F.J. (1964). The investigation of heterophoria at near and a new fixation disparity technique. The Optician. 148, 547551.
- Hoffman, L. G. and Rouse, M.W. (1980) Referral recommendations for binocular function and/or developmental perceptual deficiencies. Journal of the American Optometric Association. 51. 119-125. 15.
- Rundström. M. M. personal communication. 1995.
- Adler, P.Instructions accompanying dinosaur card.
- Evans B. J. W. (2000) Decompensated exophoria at near, convergence insufficiency and binocular instability. Optician. 219, 20-28.
- Scheiman, M. et al. (1996) Vergence facility establishment of clinical norms in a padiatric population. Supplement to Optometry and Vision Science. 73. 135.
- Optometric Management of Reading Dysfunction. Griffin. et al. (1997). Butterworth-Heinemann. ISBN 0-7506-9516-1 2.
- Optometric Management of Learning-Related Vision Problems. (1995) Schieman and Rouse. Mosby. ISBN 0-8151-6385-7.
- Visual Stress. A.J. Wilkins. (1995). Oxford Science Publications , Oxford. ISBN O 19 852 174 X.
- Pickwell's Binocular Vision Anomalies: Investigation and Treatment. (1997). B. J. W. Evans. Butterworth-Heinemann, Oxford. ISBN O 7506 2062 5
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