Ophthalmic Abnormalities and Reading Impairment Available to Purchase

Dear Editor

We are pleased that our paper has generated interest and happy to reply to the correspondents on the subject. We share with those authors, and with the many other people who contacted us, the concern that this important problem is researched and discussed. It is evident from the publicity occasioned by our paper and from communications we received that there are many different perceptions of what "dyslexia" or "reading impairment" or "vision problems" might mean.

To clarify our own position - we regard "routine vision checks" - as we stated were recommended for all children including those with severe reading impairment (SRI) - as including the provision of glasses for distant or near viewing as needed and the correction of symptomatic or psychosocial problems such as amblyopia, strabismus or convergence insufficiency. We also are aware that many developmental conditions involve a cluster of visual and cognitive impairments that can impair reading, such as cerebral palsy, extreme prematurity or cerebral visual impairment due to a variety of causes - and we interpreted the DSM V definition of SRI as excluding these other primary causes. If present, these conditions affect many domains of a child's life and need managing in a holistic way. Any conclusions drawn in our paper do not encompass these children.

We presented both the available data from a large epidemiological study and our own interpretation of them. As Professor Evans points out, interpretations can differ, and this illustrates the importance of presenting clearly and separately the data, the analysis and the conclusions. Our data were observations of a large number of children. The advantage of analysis using population based data such as ALSPAC is that these children do not have the selection bias inherent in clinic- based samples and so we can gain an overview of the frequency of problems within the whole population as well as in a subset.

The use of overlays for SRI has received much attention but was not included in our study, as there were not available concurrent data on the features that have been reported as indicating "visual stress", for example symptoms of headache, tiredness, distortion of certain images or improvement in reading with coloured overlays. However, other vision-based therapies such as interventions to improve binocular functions have been trialled as potentially useful for children with low literacy, with few beneficial effects (1). Such reports are congruent with our finding of very few abnormalities in binocularity amongst children with SRI and therefore with there being no need for additional orthotic or optometric therapies as long as normal vision care is available. There is disagreement in the literature about the use of overlays and recent evidence suggesting no effect against placebo (2). In contrast, there are also many personal accounts of individuals who do feel they have benefitted from their use of overlays. Whilst further research is needed to understand the divergence of views, our results do not suggest that manipulation of visual input would be likely to help children with SRI.

We all agree this is an important topic and one with many differences of opinion. We are grateful to the journal for the opportunity to share our data and promote discussion on this topic. Further sharing of data and discussion between parents, teachers, therapists, medical and vision practitioners are needed to identify the best practice for helping children with SRI. Ideally this may result in guidelines based on all the available evidence, that families and educationalists can use to help them decide on how best to help children with SRI.

(1)Ponsonby AL, Williamson E, Smith K, Bridge D, Carmichael A, Jacobs A, Burrill J, Ollington N, Keeffe J, Dwyer T. Children with low literacy and poor stereoacuity: an evaluation of complex interventions in a community-based randomized trial. Ophthalmic Epidemiol. 2009 Sep- Oct;16(5):311-21.

(2)Effectiveness of Treatment Approaches for Children and Adolescents with Reading Disabilities: A Meta-Analysis of Randomized Controlled Trials. Katharina Galuschka, Elena Ise, Kathrin Krick, Gerd Schulte-Korne. PLoS One 2014. February 2014 | Volume 9 | Issue 2 | e89900

Conflict of Interest:

None declared

Dyslexia is not a consequence of a refractive deficit.

Dyslexia is a consequence of a visual perception trouble. The visual parameter to be studied is the visospatial egocentric localization.The opthtalmic treatment to correct this abnormality immediatly is active prisms. This kind of prisms are not prescribed to compensate eye deviation, because this is not the case in the dyslexic patients. They are used to induce a new spatial information and to produce a reaction of the oculomotor system.The neurological pathway is the retinoculicular pathway (not the retinocortical pathway). Dyslexic children are improving the reading quality and the reading speed. Results of active prisms are wonderful but you must see to confirm.The physiological action includes proprioceptive system and this not very well known. No significant progresses has been made after Shering publication one century ago. I just can tell you it is possible to check brain modification afeter active prisms by brain mapping. It is an the low frequency areas absolutb power may pass from 1000 mv2 to 300mva in a few seconds. >

To find evidences that vision-based treatment will be useful to help children with SRI, authors must start by doing the following tests.

1-Visuospatial egocentric localization tests. Dyslexic children present usualy a wrong visuospatial localization test.

2-REY Test. This test is a visuoperceptive test: Dyslexic children present usually wrong visuoperceptive abnormalities.

3-Brain mapping registration. In Dislexic children brain mappings are showing excess of absolut power but just in the low frequencies (Delta and Teta frequencies)

After this, authors must prescribe active prisms and repeat the same above tests.

They will find that both visuospatialegocentric localization test and Rey test become normal or approche to normal parameters. In Brain Mapping Registration They will verify the originary excess of absolut power in brain mapping become normal. Figures may pass from 1000 mv2 to 300 mv2.

Authors can also verify that readind quality and reading speed become normal or almost normal after de use of active prisms.

Active prisms are not prisms to compensate ocular deviation as passive prismes are doing (this is not the case of dyslexic children, they are not heterophoric usualy, so they don?t need passive prisms ) Active prisms are low powered pismatic lenses to stimulate the brain by a slight modification of the wrong space localization ,using the retinoculicular pathway. There are precise rules to prescribe this kind of active prisms.

Doing this, authors will find vision-based evidendences for the treatment of reading inpairment.

Conflict of Interest:

None declared

Dear Editor

We read with some disquiet the paper by Creavin & colleagues on ophthalmic factors in children with reading impairment (RI). We welcome new research on this topic but the authors' choice of tests included few of those recommended to investigate the visual correlates of RI (1). Despite commenting on coloured filters the authors did not investigate Visual Stress, the condition whose symptoms are alleviated by coloured filters (2) and which co-occurs in about one third of cases of dyslexia (3). Specifically, Creavin et al did not test for Visual Stress or for the effect of coloured filters so would not have detected Visual Stress (1;2). The authors wrongly assume that conventional tests of vision are sufficient to measure the complex visual and visuo-perceptual function involved in reading. The literature review is incomplete; Uccula et al provide a more balanced review of the use of coloured filters (4).

Creavin et al. make no attempt to discover their participants' symptoms. Previous work has shown that subtle binocular vision and accommodative anomalies are associated with symptoms (5). Whilst these optometric factors are unlikely to be major causes of RI, if the anomalies cause blurred or double vision, eyestrain, or headaches then they will be additional burdens, and treatment may take away one component of the child's difficulties. With the exception of amblyopia, Creavin et al also fail to report on their participants' ocular history. It is not clear how many in their sample had received prior treatment of visual problems.

For several tests, Creavin et al obtain a continuous variable and then, rather than comparing the group means (e.g., by t-test), they reduce the data to a normal/abnormal dichotomy. This reduces the power of the analysis to detect change. Often the division seems arbitrary, lacking any rationale for the cut-off selected. For some variables (e.g., accommodation, convergence) the authors fail to state where the cut-off was set.

Considering the coarse tests that the authors used, it is noteworthy that they found abnormal ophthalmic function in 1 in 5 children with RI. For example, the RI group were 3 times more likely to "fail" the stereotest, even with the cut-off that the authors used. The authors go on to hypothesise that the reduced binocular functions could be the result of dyslexia although they present no data to support this conjecture. Indeed, previous research found that the visual correlates of dyslexia are not secondary to the poor reading (5). The authors go on to say that treatments will not help; but no treatments were evaluated.

We agree that the visual correlates of dyslexia are subtle and not likely to be major causes of RI (1), but we take issue with Creavin et al's simplistic agenda that visual factors are irrelevant in RI. In a few cases, visual factors co-occur with RI and then a visual treatment (e.g., glasses, eye exercises, coloured filters) will give the child better access to the extra teaching that they will no doubt also need. Creavin et al find evidence to support this view, despite the conclusions they draw.

Reference List

(1) Allen PM, Evans BJW, Wilkins AJ. Vision and Reading Difficulties. London: Ten Alps; 2010.

(2) Monger L, Wilkins A, Allen P. Identifying visual stress during a routine eye examination. J Optom 2014 Nov 11.

(3) Kriss I, Evans BJW. The relationship between dyslexia and Meares -Irlen Syndrome. J Res Reading 2005;28(3):350-64.

(4) Uccula A, Enna M, Mulatti C. Colors, colored overlays, and reading skills. Frontiers in Psychology 2014;5.

(5) Evans BJW, Drasdo N, Richards IL. Investigation of accommodative and binocular function in dyslexia. Ophthal Physiol Opt 1994;14(1):5-19.

Conflict of Interest:

AJW receives an Award to Inventors from the Medical Research Council based on a proportion of royalties on sales of the Intuitive Colorimeter, the Wilkins Rate of Reading Test, and (until recently) the Intuitive Overlays.