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The role of the optometrist with underachieving children.

Optometrists *

Dispensing opticians ***

In this article, the author presents a series of cases of children that presented to his practice to identify potential visual factors influencing academic underachievement.


When children underachieve at school, parents or teachers may suspect a visual problem and consult an eyecare practitioner (ECP). A great deal of the information presented to children during their education is visual, and obviously visual problems could contribute to underachievement. In the UK, many visual problems go undetected, (1,2) and so it would seem advisable for children who underachieve to have a thorough optometric assessment. However, it is important to put the role of the ECP in perspective. The mainstream view of education experts is that there are two distinct forms of reading disorder: dyslexia; and reading comprehension disorder. (3) Dyslexia is caused by decoding difficulties, causing sufferers to experience poor understanding of the structure of sounds within words (phonemic awareness), letter-sound knowledge, and rapid automatised naming.

Research has identified visual correlates of dyslexia, most notably a magnocellular deficit (a sensory factor) and binocular instability (a motor condition); (4) which are associated with each other. (5) The evidence is that although these conditions are sometimes associated with letter or word confusions, (6-8) they are unlikely to be major causes of dyslexia. (5,9-11) It has been estimated that about 15% of people with dyslexia have binocular instability, and the condition is unlikely to require treatment in every case as it will not necessarily be associated with symptoms. (12) If symptoms are present--for example, words blurring or doubling (13)--in a dyslexic patient with binocular instability, (10) this does not mean that the binocular instability is causing the reading difficulty. Rather, the binocular instability is likely to be a co-occurring condition. Treatment should not be expected to cure the reading difficulty but may alleviate visual symptoms.

Visual stress (VS), also called Meares-Irlen syndrome, (14) is a more controversial condition. Recent controversy is at least in part attributable to some reviews, (15) including studies of populations that were not selected as having VS and with study designs unsuitable for evaluating VS.16 A systematic review (17) of studies of people with VS that used the 'intuitive system' (18-20) supports the existence of VS as a co-occurring factor affecting a minority of people (~20%) with dyslexia. Both sides of the controversy agree that a stronger evidence base is desirable, (15,17) as in many areas of optometric practice. (21) Recent progress in moving towards a standardised definition of VS is a useful step. (22)

It is clear from the above figures for the prevalence of binocular instability (15%) and VS (20%) in those with dyslexia that most people with dyslexia do not have visual problems. Other optometric conditions that are no more prevalent in dyslexia than in the general population, for example, refractive error, (9) can also be relevant. (23) Optometric anomalies that are present in a person with dyslexia require treatment only if they are causing symptoms or are likely to be contributing to the child's difficulties at school. The symptoms that are pertinent to the optometric conditions described above are non-specific, and therefore differential diagnosis by an ECP is required.

The purpose of this article is to present case studies illustrating this process. The case studies are presented 'as seen' in a busy community optometry practice, warts and all. The first case will be described in some detail, and the other cases more briefly.

Case 1


Case 1 (CI), a 16-year-old female student, consulted the author in January 2015 (see Figure 1, page 74). This case has been selected because many of the features are typical of VS. When CI first looked at a book (or, less frequently, a whiteboard), text appeared clear, but after reading a few lines it blurred, jumped, and doubled. These symptoms only occurred with text, which also caused sore and tired eyes. Studying caused headaches, which resolved when she took a break and did not occur on holidays. She found that holding text close alleviated the symptoms and first remembers noticing her symptoms in year seven when reading music.

There is no significant refractive error and unaided vision, binocular vision tests, stereoacuity, and accommodative function are all within normal limits. In the pattern glare test (PGT), (see Figure 2) patients first view a control grating (Pattern 1) and report whether they experience any of the symptoms listed, which are summed. The same procedure is followed for Pattern 2. Pattern 1 is a control grating to check for suggestibility, because most people experience few symptoms on viewing such a low spatial frequency grating. C1 reported two symptoms on viewing this grating (recorded as PGT 1-2). People with VS typically experience quite marked symptoms on viewing Pattern 2, including aversion. (24) The author records this as a grade of 1 to 5, where 1 is a mild aversion and 5 represents a patient who tries to look away and exclaims that it is unpleasant to view. The record annotation (2-5-4) indicates, on viewing Pattern 2, a marked aversion (grade 5) and report of 4 of the symptoms listed on Figure 2, which research indicates is suggestive of VS. (24,25)

The Intuitive Overlays test18 starts with asking the patient about any symptoms on viewing crowded text, and CI reported that this text appeared to blur, move (shimmer), and words appeared too close together. When tested with 30 combinations of overlays she preferred a single blue, showing a consistent response, and reported that the overlay improved her symptoms. The effect of the overlay was assessed with the Wilkins rate of reading test (WRRT) (19) and the result (recorded under 'CV Test's) was that CI read slowly without the overlay (89 words per minute; mean of two results) and with the overlay 62% faster (144 words per minute; mean of two results). The latest recommendation (26) is that an increase in reading speed of 15% or more with filters is likely to indicate an improvement that exceeds any due to random variation, so 62% is a marked improvement.

Primary diagnosis

A recent paper used a Delphi method to discover the approach taken to diagnose VS from some of the most experienced practitioners in the UK. (22) The outcome of this study was to suggest the diagnostic algorithm in Figure 3. C1 was examined before the results of the Delphi study were known, and at that time the author did not always ask all the questions listed in Figure 3. However, CI does meet the clinical signs in Figure 3, being positive for the WRRT and PGT criteria.

Alternative diagnoses or explanations

Symptoms of headaches, text blurring moving, and doubling could be caused by a binocular vision anomaly. (13) However, there was no movement seen on cover testing minimal deviations on dissociation tests, Mallett fixation disparity test results were within normal limits, (13) and Evans' algorithm for detecting decompensated heterophoria (13,27-29) was passed. In the author's opinion, the small distance esophoria on Maddox rod is not significant and the patient's symptoms mostly related to near vision. Vergence facility and accommodative facility are additional tests that some practitioners would have completed, but there were no reports of difficulty changing focus. C1's report that holding text close alleviated symptoms, is not suggestive of a binocular or accommodative anomaly.
Figure 3 Putative diagnostic indicators for VS22

At least three of the following six typical symptoms:

1. Words move

2. Words merge

3. Patterns or shadows in text (eg, 'rivers')

4. Text seems to stand out in 3D above the page

5. Words or letters fade or darken

6. Discomfort with certain artificial lights and flicker


At least two of the following three signs from investigations:

1. Voluntary unprompted use of an overlay for three months or more

2. Overlay improves performance at the WRRT by
[greater than or equal to] 15%

3. PGT result >3 with mid-spatial frequency grating

A benefit from coloured filters could, conceivably, be attributable to latent hyperopia or accommodative dysfunction (see Figure 4, page 76), with longitudinal chromatic aberration (LCA) causing the patient to choose a blue overlay, in the way that an uncorrected hyperope finds green clearer on the duochrome test. However, the amplitude of accommodation is good and the accommodative lag within normal limits. Additionally, research shows that uncorrected hyperopia in pre-presbyopes has a minimal effect on performance of the WRRT. (30)

It is possible that somebody had suggested the symptoms of VS to CI and she manifested these in response. Similarly, the overlay could have been selected for one of the non-clinical confounding factors in Figure 4. Although a 62% improvement at the WRRT indicates a powerful effect, this does not exclude a placebo effect. (31) However, a placebo effect or the other putative alternative diagnoses in this section would not explain the PGT result.


C1 was dispensed with an overlay of her preferred colour to try for one month. The Delphi study recommends a longer trial of three months, although it is questionable whether a trial is necessary with adults. (12-32) C1 returned in February 2015 after using her overlay and reported that it was helping, alleviating the symptom of words merging and reducing the frequency of headaches. It is noteworthy that C1 had not reported text merging at the initial appointment; sometimes, patients do not initially report a symptom to which they are habituated. C1 was tested with the Intuitive Colorimeter. (12,20) This test starts with asking the patient about their symptoms when they view crowded text with white light. Then, the practitioner compares a range of colours (hue angles) with white (in pseudo-random order) and records the effect these colours have on symptoms, using the fan chart on Figure 5, page 76. Colours are represented in a circle, and a classic response is to show complementarity: an area where the symptoms are greatly reduced (recorded as +2), an area opposite where the symptoms are exacerbated (-2), with colours between these two having less effect on symptoms (0, +1, -1). A minority of patients, including CI, have a different pattern, demonstrating two loci of benefit. With CI, the two areas that alleviate symptoms are centred on 0[degrees] hue angle (a red colour) and 180[degrees] to 210[degrees] (a blue colour). The latter area was associated with the most marked reduction in symptoms, and so this was selected for more detailed testing using the target chart. At this stage, the saturation is tuned, then the hue, again the saturation, then hue, to find the optimum colour. The precision of the required colour (illustrated with the arrows in Figure 5) varies from one person to another. (33,34)

After colorimetry, the final preferred colorimeter setting (hue 190[degrees], saturation 30, no attenuator, consistent response judged as 8/10) is converted to a precision tinted lens specification12 and the optimal colour is checked using precision tinted trial lenses. In patients showing greatest precision, this stage allows the practitioner to check the required colour using lighting conditions and tasks that mimic the patient's everyday activities. Following this, CI was dispensed with piano precision tinted spectacle lenses.

C1 returned in November 2016, aged 17 years, reporting that the precision tinted lenses had helped 'a lot,' improving perception of text and reducing the frequency of headaches. She returned because the headaches were now increasing in frequency. The optometric findings were unchanged, and colorimetry revealed a change in the colour of tint required, as shown in the lens transmission curves (see Figure 6, page 77).

Discussion of case 1

It is interesting that previous optometrists had prescribed CI with spectacles and eye exercises. It is not surprising that ECPs, faced with a highly symptomatic patient, try conventional optometric approaches. However, the optometric findings when the author saw CI were normal and the patient reported a major instant effect of colour on her symptoms, unlike previous interventions.

VS has been attributed to a hyperexcitability of the visual cortex. High contrast patterns with spatial frequency near the peak of the contrast sensitivity function (see Figure 2, right panel) are likely to trigger symptoms in such patients. (34-35) Lines of text form a striped pattern that can be problematic for some individuals. (36) Any intervention that will reduce the strength of the signal to the visual cortex is likely to be helpful, and coloured filters are a way of filtering the signal without adversely affecting the visibility of text. It is, therefore, quite possible that in some cases coloured filters will not completely alleviate the symptoms of VS, and this concurs with the author's clinical experience.

The finding that different people need individually prescribed colours, and the colour sometimes needs to be defined with some precision, is harder to explain. One possibility is that hyperexcitability within the visual cortex is localised and, by virtue of the topographic encoding of chromaticity, (37) the optimal colour may reduce excitation in hyperexcitable areas. (34,35)

There has recently been a debate about the precision required for colorimetry, and clinicians who use the intuitive colorimeter will be familiar with variations in precision between patients. Uncommon patients, like C1, who report two loci of benefit may have an impact on research on precision. Some patients report that one colour alleviates certain symptoms, while another improves different symptoms. The patient initially may choose the colour that helps the symptom that they then find most bothersome and then, over time, another symptom predominates resulting in a change in colour. This could account for changes in colour, or these could be attributable to developmental changes or confounding factors (see Figure 4). Colour changes are much less common in adults than children. Preliminary evidence suggests that VS may be more prevalent in dyslexia than in good readers (38) or that VS only has a significant effect on reading speed in individuals with dyslexia. (39) Any relationship with dyslexia may be explained by a genuine association between pattern glare and dyslexia (33) (although not in profound dyslexia), (40) by poor readers being more distracted by the symptoms of VS on a page because the meaning of text is less apparent to them, (33) or because the greater concentration they require during reading increases cortical hyperexcitability.

As noted in the introduction, optometric factors are not likely to cause dyslexia and people who underachieve at reading and have visual symptoms require both an examination by an ECP and an assessment for dyslexia, for example, by an educational psychologist. The author recommended the latter for CI.

Case 2

Case 2 (C2), an 11-year-old girl, was referred to the author in July 2015 because she was a reluctant reader. This case is considered in brief, because the main point illustrated is that many patients with reading difficulties require no optometric intervention.

Examination (see Figure 7) revealed a marginal degree of myopia, but the minimal improvement in VA and a +1.00D test indicated that the right eye subjective refraction was slightly over-minused. Glasses were not prescribed but a check in six months was recommended to monitor the low myopia and optic discs, which showed borderline signs of drusen by routine OCT, but looked normal by ophthalmoscopy.

The tests of binocular co-ordination and accommodation (described in more detail for CI) were all within normal limits. C2 did not have the characteristic symptoms of VS and did not manifest any of the clinical signs of VS. As explained in the introduction, most patients reporting underachievement at school have no optometric problems and need no optometric treatment. The role of the ECP in these cases is to reassure the patient and parents, recommend routine eyecare at appropriate intervals, avoid prescribing unnecessary optometric interventions, and signpost the parents to other professionals who can assess and address the child's academic underachievement.

Case 3

Case 3 (C3), a nine-year-old girl, consulted the author for the first time in March 2018. There was a history of intermittent right esotropia seen solely by the mother at age one to two years, which resolved. This was not investigated at the time, but at subsequent eye examinations, including one six months before she saw the author, the family was told that no abnormalities were present. Retinoscopy (see Figure 8, page 78) revealed a suspicious degree of hyperopia and at one point the author observed a markedly more hyperopic reflex. During subjective refraction there were also signs of latent hyperopia, and a cycloplegic refraction revealed a marked degree of hyperopia.

It seems likely that the significant hyperopia was the cause of the intermittent esotropia observed in the preschool years. It is not clear why this deviation resolved; nonetheless, the marked hyperopia clearly puts the patient at risk of esotropia (Percival's criterion is failed), (13,41) and it seems likely that either now or before long the hyperopia could present a barrier to comfortable and accurate reading. (42-45)

There are at least three dilemmas in this case. The first is deciding what prescription to give, and the author was reluctant to correct too much of the hyperopia for several reasons: the patient had good acuities and few symptoms; a higher prescription might have caused spectacle non-tolerance as the child was used to accommodating for distance vision; and the child was close to orthophoric and had a high AC / A ratio (5A/D), so a higher prescription could have caused a decompensated exo-deviation. The author decided to correct about half the hyperopia initially but counselled the mother that the prescription was likely to increase. The second controversy is when spectacles should be worn. The author recommended for concentrated vision (schoolwork and homework), but some practitioners would recommend full-time wear. A third uncertainty is whether the patient had anisometropia, which was indicated by non-cycloplegic retinoscopy (1.50D aniso) and subjective (1.00D), and amplitude of accommodation (Acc, measured at the beginning of the examination without refractive correction); but not supported by the retinoscopy (monocular estimate method (MEM)) findings. Cycloplegic refraction revealed 0.25D anisometropia. Some practitioners would have adhered rigidly to the degree of anisometropia found by cycloplegic, but in view of the other findings the author corrected 0.75D, planning to review in three months. The symptoms were not strongly indicative of VS, the pattern glare test was negative and although an overlay was preferred, C3 only reported a minimal effect on symptoms. Therefore, an overlay was not prescribed.

General discussion

Visual factors are not the main cause of educational underachievement, although visual problems may contribute to underachievement in some cases. The WRRT is designed to be sensitive to visual factors and to be minimally influenced by reading skill. (19) Therefore, a marked improvement at this test with an optometric intervention does not necessarily indicate that there will be such a large impact on normal reading, although a benefit is likely.

The cases presented in this article support the contention that children who underachieve educationally should undergo a thorough optometric assessment. The cases highlight the need for an assessment for refractive error and VS. A previous series of cases highlight other conditions that can be mistaken as VS, including astigmatism, decompensated heterophoria, and (exceptionally) ocular pathology. (23) A recommended routine for a full optometric investigation of children who underachieve (12) includes tests that are beyond the GOS sight test. In some areas, NHS enhanced services may fund these tests whereas in others they may need to be privately funded.

This article has not dwelt on the issue of dyslexia as its diagnosis is not highly relevant to the ECP. Any child who is underachieving, whatever the educational diagnosis, could have a co-occurring visual factor, but it was noted in the introduction that most children who underachieve do not. For example, although visual symptoms have a higher than usual prevalence in dyslexia, (10) most people with dyslexia do not have visual symptoms. (46) Those with visual symptoms are more likely to be referred to ECPs; this referral bias might lead ECPs to over-estimate the prevalence of visual problems.

Exam questions and references

Under the enhanced CET rules of the GOC, MCQs for this exam appear online at Please complete online by midnight on 6 July 2018. CET points will be uploaded to the GOC within 10 working days. Visit www., and click on the 'Related CET article' title to view the article and accompanying 'references' in full.

Prof Bruce Evans BSc, PhD, FCOptom, FAAO, FEAOO, FBCLA, DipCLP, DipOrth

About the author

* Professor Bruce Evans works as a community optometrist in Essex, is director of research at the Institute of Optometry, and a visiting professor at City, University London and London South Bank University.

* Acknowledgement and disclosures The author is grateful to several colleagues for helpful comments on drafts of this article. Prof Evans receives honoraria for lectures on this topic and is an unpaid committee member and secretary of the notfor-profit Society for Coloured Lens Prescribers (www.s4clp. org). The Institute of Optometry receives donations from i.O.O. Sales Ltd which sells, among other products, Intuitive Overlays, the Pattern Glare Test, and the Wilkins Rate of Reading Test.

Learning objectives

* Be able to elicit relevant detail from children who are underachieving academically (Group 1.1.2)

* Understand the range of assessments required to assess children who are underachieving academically (Group 7.1.3)

* Understand the importance of undertaking a careful binocular vision assessment in children who are underachieving academically (Group 8.1.1)

* Be able to elicit relevant detail from children who are underachieving academically (Group 1.1.2)

* Understand the range of assessments required to assess children who are underachieving academically (Group 7.1.1)

Caption: Figure 1 Functional tests of Case 1. Ocular examination, including ophthalmoscopy, is not shown on this screenshot and was within normal limits, with no flare in the anterior chamber by biomicroscopy. The Presenting Complaint box overflowed, and the complete text is reproduced above. Special invest, special investigation of visual function; Spx, spectacles; LEE, last eye examination; HA, headaches; VS, visual stress; fus res, fusional reserves; text, symptoms reported in the Intuitive Overlays test;'8 c, with (except in stereopsis test when refers to Randot 2 circles subtest); s, without (except in Randot 2 stereopsis test when refers to random dot shapes subtest); PGT, pattern glare test (see brelow); MEM, monocular estimate method of retinoscopy to assess accommodative lag

Caption: Figure 2 Pattern glare test (a third pattern provides limited information and the author no longer uses this) (c) AJ Wilkins & BJW Evans 2001, 2012

Caption: Figure 4 Schematic diagram to illustrate potential reasons why children might choose a coloured filter on first testing. LCA, longitudinal chromatic aberration. The lower three boxes may be considered non-clinical confounding factors. Reproduced from Evans and Allen (17)

Caption: Figure 5 Intuitive colorimeter first test result for C1

Caption: Figure 6 C1 precision tinted iens specification from February 2015 (top) and November 2016 (bottom)

Caption: Figure 7 Functional tests of C2, Ocular examination, including ophthalmoscopy, is not shown on this screenshot and was within normal limits, except for possible very mild optic nerve drusen by OCT. For key see Figure 1

Caption: Figure 8 Functional tests of C3 Ocular examination, including ophthalmoscopy, is not shown on this screenshot and was within normal limits. For key see Figure 1

Optometrists *

Therapeutic opticians **

Dispensing opticians ***

Contact lens opticians ****
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Title Annotation:Learning difficulties
Author:Evans, Bruce
Publication:Optometry Today
Date:Jun 1, 2018
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