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The role of the optometrist with underachieving children and visual stress: This article outlines case presentations of children underachieving academically as seen in clinical practice.

Optometrists ****

Dispensing opticians **



In a previous article in Optometry Today, (1) it was noted that the mainstream view of education experts is that visual factors are not major causes of academic underachievement. (2) Visual correlates of dyslexia have been identified and include, magnocellular deficit and binocular instability. (3,4) These factors can be associated with letter or word confusions, (5-7) but are unlikely to be major causes of dyslexia. (4,8-10) Around 15% of those with dyslexia will have binocular instability although the condition may not necessarily be associated with symptoms or other difficulties and, therefore, is unlikely to require treatment in every case. (11)

Visual stress (VS) also termed Meares-Irlen syndrome (12) is a condition not without controversy, which is at least in part attributable to some reviews (13) including studies of populations that were not selected as having VS and unsuitable study designs. (14) A systematic review (15) of studies of people with VS that used the 'Intuitive system' (16-18) 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, (13,15) as is the case in many areas of Optometrie practice. (19) Recent progress in moving towards a standardised definition of VS is a useful step. (20)

The purpose of this article is to present new case studies illustrating the role of the optometrist in assisting patients with academic underachievement and /or visual stress. The case studies are presented 'as seen' in a busy community optometry practice.

Case 1


Case 1 (C1) first consulted the author in February 2016 when she was a 17-year-old A-level student, hoping to study for an allied healthcare career at university (see Figure 1). This case has been selected because many of the features are typical of VS. When C1 first looked at a book, text appeared clear, but after a while she experienced anomalous visual effects (text appeared to blur and swirl on the page) and headache. The main trigger for her headaches was reading but they could also be triggered by exercise, computers, or bright light. C1 has anisometropia and was first prescribed glasses in 2014, which in 2016 she had started wearing again. C1 reported that the glasses improved the clarity of text but did not resolve the anomalous visual effects.

There was no significant change in refractive error and corrected visual acuities, colour vision, visual fields, and ophthalmoscopy (not shown) were all within normal limits. All the accommodative, binocular vision (except motility), pattern glare, and overlay tests were carried out with refractive correction. C1 has some marginal signs of binocular instability (fusional vergence dysfunction) in that both the convergent and divergent near fusional reserves (N FR) are low. (21) However, the lack of any movement on cover test, low dissociated deviation ('muscle balance', assessed by Maddox rod and Maddox wing), and negligible aligning prism on the Mallett unit all indicate that the subtle binocular instability is unlikely to be causing problems. Similarly, the finding of 2.5[degrees] in-cyclotorsion on the Maddox wing is more likely to reflect a good observer than a significant anomaly. The amplitude of accommodation is lower than average, but more than adequate for typical viewing distances and accommodative lag is within normal limits.

In the pattern glare test (PGT) (see Figure 2, page 62), patients first view a control grating (Pattern 1) and report whether they experience any of the symptoms listed; which are then summed. The same procedure is followed for Pattern 2. Pattern 1 is a control grating to check for suggestibility: most people experience few symptoms on viewing such a low spatial frequency grating. CI 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. (22) The author records aversion 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 (2-3-6) indicates, on viewing Pattern 2, a definite aversion (grade 3) and reports of six of the symptoms listed, which is indicative of VS. (22,23)

The Intuitive Overlays test16 was carried out while wearing spectacles and starts by asking the patient about any symptoms on viewing crowded text. CI reported that this text appeared to 'spin', blur, and caused discomfort. Text appearing to move, flicker, or shimmer is often reported in VS. (24,25) The symptom of text appearing to 'spin' is a less common, but nonetheless recognised, (26) symptom of VS.

An alternative hypothesis to visual stress, that the symptoms could result from binocular instability, was investigated by occluding each eye in turn, but occlusion worsened the perception of text. Contrastingly, coloured overlays had a marked effect on symptoms when viewing text, with a double blue combination significantly reducing symptoms. The effect of the overlay was assessed with the Wilkins rate of reading test (WRRT) (17) and the result (recorded under 'CV Test') was that CI read 25.5% faster with the overlays. The latest recommendation 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. (27)

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. (20) The outcome of this study was to suggest the diagnostic algorithm in Figure 3, page 62. CI was examined before the results of the Delphi study were known, and at that time the author did not ask all the questions listed in Figure 3. However, C1 does meet the clinical signs in Figure 3, being positive for the WRRT and PGT criteria.

Alternative diagnoses or explanations

Latent hyperopia is a possibility and the difference between the retinoscopy and subjective result, slightly reduced accommodative amplitude, and stereoacuity results made the author consider undertaking a cycloplegic refraction. However, the equality of amplitude of accommodation in each eye, good and reasonably balanced monocular estimate method (MEM) retinoscopy result, lack of significant eso-deviation, and patient age, offered reassurance that a cycloplegic was unlikely to be useful. The results at the next two eye examinations (2017 and 2018) supported this decision.

As noted above, symptoms of headaches, and text blurring and moving could be caused by a binocular vision anomaly. (21) However, the clinical findings were mostly within normal limits and the effects of monocular occlusion do not support this hypothesis.

Nonetheless, as a precaution C1 was asked to return in six months for the binocular vision and accommodation to be monitored.

It is possible that somebody had suggested the symptoms of VS to C1 and she manifested these in response. Similarly, the overlay could have been selected for one of the non-clinical confounding factors in Figure 4, for example, placebo effect. However, such effects would not explain the PGT result.

Figure 3 Putative diagnostic indicators for VS20
Figure 3

At least three of the following six typical symptoms:

1. Words move

2. Words merge

3. Patterns or shadows in text (for example, "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 investigation:

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


C1 was dispensed with an overlay of her optimal colour to try for one month. Nowadays, the Delphi study recommendation of a longer trial of three months would be followed, although it is questionable whether a trial is necessary with adults. (11,28) C1 returned in March 2016 reporting that: 'Overlay helping stops words spinning and blurring, so can read easier. No headache recently.'

C1 was tested with the Intuitive Colorimeter, (11,18) as described elsewhere. (1) The precision of the required colour varies from one person to another, (29,30) and with C1 there were several colours initially that were preferred to white (see Figure 5, page 64). The final choice was near the centre of a fairly wide range of colours, illustrated with the arrows in Figure 5.

After colorimetry, the final preferred colorimeter setting (hue 130[degrees], saturation 30, no attenuator, consistent response judged as 8/10) is converted to a precision tinted lens (PTL) specification11 and the optimal colour is checked using precision tinted trial lenses. Following this, C1 was dispensed with prescription PTLs for studying indoors.

C1 returned eight months after the initial eye examination and reported that: 'PTL help, stop words moving and blurring and stop swirling patterns; has definitely helped school performance.' Colorimetry was not checked at this appointment (as only six months had elapsed) but interestingly when wearing the PTL there was an improvement in amplitude of accommodation (R12D, L11D) and Randot stereoacuity (shapes 125," circles 40"). It is tempting to attribute the improvement to the PTL, although other explanations are also possible, for example, regression toward the mean, placebo effect, practice effect. (31) Other test results were similar to before.

In April 2017, CI returned for a repeat eye examination and colorimetry. She was still using the PTL as before and finding them helpful, but reported that white surfaces appeared slightly pink for a little while after removing them. This may be attributable to colour adaptation. The refractive error had only changed marginally, and tests of binocular vision and accommodation were within normal limits. The Intuitive Colorimeter and PTL testing indicated a change in hue (from a combination of turquoise and green dyes to a combination of turquoise and blue) and a lighter colour was accepted. In view of the symptom, the PTL were changed. At the most recent appointment, in June 2018, the clinical and colorimetry findings were all unchanged. CI is now studying an allied healthcare subject at university. In the author's experience, while the PTL specification sometimes changes in children, it is unlikely to change in adults and CI was, therefore, advised that routine colorimetry was no longer required, unless her symptoms recurred. She had an untinted pair of prescription spectacles for use outdoors, and so is able herself to reflect on whether the PTL continue to be helpful.

Case 2

An 11-year-old girl (C2), presented for the first time in February 2018. Examination revealed some variable responses but no consistent abnormalities (see Figure 6, page 65). C2 did not report any of the symptoms that are typical of VS and had a negative PGT. Some patients become habituated to their symptoms and only report these when an intervention that reduces the symptoms is presented, for example, refractive correction or coloured overlay. Therefore, it is still useful to test children who underachieve at school with overlays, even if they do not report symptoms in the first instance. During the Intuitive Overlays test, C2 chose a coloured overlay and reported a benefit, but the overlay did not result in an improvement at the WRRT. None of the Delphi criteria were met and therefore C2 was not issued with a coloured overlay. This case is a reminder that the coloured overlay test involves an element of suggestion and when patients report an improvement with coloured filters this does not necessarily mean that an overlay should be dispensed. In C2, it seems likely that one of the 'non-clinical confounding factors' in Figure 4 explains the reported benefit. C2 was advised visual factors are not likely to be contributing to her difficulties, but was seen again soon to monitor the variable responses, which improved.

Case 3

As when prescribing for low refractive errors or marginal binocular vision anomalies, the experienced clinician will be mindful of cases like C2 and will take account of other relevant factors. For example, Case 3 (C3; which is not illustrated and only described in brief) is a 12-year-old girl. The child had been diagnosed with dyslexia. No one had suggested that the child should try coloured filters, and none of the child's classmates were using these. C3 was using coloured plastic folders to organise her work and noticed that a mint-green folder improved her perception of text. Her mother investigated this on the internet and booked an appointment. The child was optometrically normal, but on testing with the full range of Intuitive Overlays she preferred an aqua overlay, which resulted in a 50% improvement on the WRRT. The other notable feature about this case is that, because none of her classmates were using PTL, this child did not want to be the first in her class to use them. Rather than testing with the Intuitive Colorimeter all she required was a coloured overlay and a letter to school requesting that wherever possible they used blue /green coloured paper.

Case 4

A 12-year-old boy (C4) attended for consultation in June 2016. He had been prescribed PTL in the past, and at his last eye examination five months before he had been told that his eyes were normal. The author found reduced visual acuities, no significant refractive error, poor stereoacuity, and reports of symptoms on both the control and pattern glare grating (see I. Figure 7). At this point, there was suspicion of a visual conversion reaction (psychogenic) (32) and in view of the esophoria the plan at this stage was to call the child back for a cycloplegic refraction. However, ocular examination and OCT scans indicated a different aetiology. Ophthalmoscopy revealed a lightly pigmented fundus (the child was blond) and no macular reflexes. OCT scans showed foveal hypoplasia (see Figure 8, page 66) and biomicroscopy of the anterior segments confirmed transillumination.

C4 seemed to fit the diagnosis of (ocular) albinism but, even on careful viewing with the biomicroscope, there was no evidence of nystagmus, which is expected in this condition. (21) By coincidence, there is an Hospital Eye Service (HES) unit not far from the patient's home in the East of England with expertise in nystagmus research who see many cases of ocular albinism. The patient was referred to this unit, via the GP, making sure that the parents had a copy of the letter to take to the HES.

The author received no reply to the referral and after a few months telephoned the mother who confirmed that the child had been assessed, digital eye movement analysis revealed subtle nystagmus, and the diagnosis had been confirmed. Providing new PTL in this case was delayed pending HES opinion; however, the mother reported no advice on tints from the HES. C4 also had a specific learning difficulty and had found his previous PTL helpful but preferred the new tint found at the most recent examination. It was explained that PTL will not protect the eyes from sunlight and that C4 must wear appropriate sun protection outdoors. The author agreed to send them a prescription with the PTL specification for them to take to a local practitioner for dispensing with instruction to wear with schoolwork. It seems possible that, in this unusual case, there may be a colour-specific element of VS overlying a non-colour-specific photophobia from ocular albinism.

Case 5

A 38-year-old female teacher (C5) attended for examination in 2001. She had a history of specific learning difficulties (although not formally diagnosed) and had suffered from headaches since early teens. A neurologist had investigated the headaches, and some were classified as cluster, others as migraine. (33) At this first appointment the patient estimated that she experienced 240 days of headaches in a typical year. She was aware of two triggers: stress and artificial lighting. There was a family history of migraine (both parents) and dyslexia (son).

Optometrie examination was normal but in view of intraocular pressure (IOP) asymmetry she was scheduled for yearly recall (IOP R19 L15, C:D ratio 0.5 in each eye, normal visual fields). C5 showed a very consistent response to testing with the Intuitive Colorimeter. She was prescribed piano PTLs for use at work and when reading. At follow-up one year later, she reported that the headaches were rare when wearing the PTL but were still frequent when not worn and had recurred recently after losing her glasses. A similar colour was found (which changed very little in subsequent years) and new PTLs were ordered. The records from 2004 indicate that at that time the headaches were only occurring without PTL.

Over the years to 2016 little changed, but at this appointment the records show some interesting observations from the patient about the continuing benefit she experienced from PTL. She noted that they were particularly helpful at preventing headaches when she viewed text printed with certain fonts, and under fluorescent lights. These unprompted observations are concordant with the cortical hyperexcitability model for VS. (25,34,35)

In 2016, the patient (aged 54 years) reported that the headaches had significantly reduced in frequency and were now rare, even without PTL. This can happen around menopause, and indeed even with men, headaches sometimes reduce with age, perhaps explained by reducing cortical hyperexcitability. (24) It is always preferable to take a patient out of PTL if possible, and it was recommended that C5 try without PTL. At the next appointment she reported that she was managing well without the lenses. A sceptic would point out that despite over 10 years of voluntary use of PTL and reports of reduction of migraine, these effects could be attributable to a placebo effect. The fact that C5 is a down-to-earth, unexcitable, teacher does not preclude this hypothesis. Alternatively, cortical hyperexcitability is widely considered to be a feature of migraine (36-38) and has been implicated as the mechanism for the benefit from PTL in some cases of migraine. (39-42) However, although some migraine sufferers report visual triggers, (43) it is probably only a minority of cases of migraine who would be helped by PTL. (44)

As an important aside, in 2016 C5's OCT glaucoma indices appeared to be worsening. The IOPs had increased from R19 L15 in 2001 to R21 L23, but pachymetry was circa 570[micro]m in each eye and visual fields still remained normal, with wide open anterior chamber angles. In view of the worsening OCT findings, C5 was referred to a glaucoma specialist for a second opinion. Migraine is associated with an increased risk of glaucoma (45) and this is worth bearing in mind when monitoring migraine patients.

General discussion

As recently discussed in OT, (1) only a minority of people with dyslexia have visual problems and these problems are best thought of as co-occurring factors, rather than potential causes of dyslexia. Optometric interventions, whether refractive corrections, vision therapy, or coloured filters, should not be thought of as a treatment for dyslexia or other specific learning difficulties; however, all who wish to read are likely to find it easier when text is clear, stable, and comfortable and if Optometric interventions help achieve this, they are likely to be worthwhile.

The cases presented in this article support the notion that people who underachieve educationally or who have visually precipitated headaches should undergo a thorough Optometric examination, including an assessment for VS. Previously reported case studies highlight other conditions that can be mistaken as VS, including astigmatism, decompensated heterophoria, ocular pathology (cataract), (46) and refractive error. (1) This series adds ocular albinism to the list of conditions that need to be considered in the differential diagnosis of visual stress. Therefore, a full eye examination (including orthoptic assessment) is an important precursor to the prescribing of PTL.

Acknowledgement and disclosures

The author is grateful to several colleagues for helpful comments on drafts of this article. Mr Evans receives honoraria for lectures on this topic and is an unpaid committee member and secretary of the not-for-profit Society for Coloured Lens Prescribers (

The Institute of Optometry, an independent charity, 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.

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 12 October 2018. You will be unable to submit exams after this date. Please note that when taking an exam, the MCQs may require practitioners to apply additional knowledge that has not been covered in the related CET article.

CET points will be uploaded to the GOC within 10 working days. You will then need to log into your CET portfolio by clicking on 'MyGOC on the GOC website ( to confirm your points.

Visit, and click on the 'Related CET article' title to view the article and accompanying 'references' in full.

Course code: C-60311 Deadline: 12 October 2018

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)

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

* Professor Bruce Evans works as a community optometrist in Essex (where the cases in this article were seen), as director of research at the Institute of Optometry, and as visiting professor to City, University London and London South Bank University.

Caption: Figure 1 Functional tests of Case 1. Ocular examination, including ophthalmoscopy, is not shown on this Screenshot and was within normal limits. The Presenting Complaint box overflowed, and the complete text is reproduced above the Screenshot of the computerised main record. Y10, year 10; Special invest, special investigation of visual function; Spx, spectacles; LEE, last eye examination; HA, headaches; VS, visual stress; FR, fusionai reserves; text, symptoms reported in the Intuitive Overlays test;16 R, right; L, left; B, both; c, with; s, without (except stereopsis, measured with Randot 2 stereopsis test, when S refers to random dot shapes subtest and C refers to contoured circles subtest); PGT, pattern glare I test (see below); MEM, monocular estimate method of retinoscopy to assess accommodative lag; BV, binocular vision

Caption: Figure 2 Pattern glare test (a third pattern provides limited information and the author no longer uses this)

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 (15)

Caption: Figure 5. Intuitive colorimeter first test result for C1

Caption: Figure 6 Functional tests of Case 2, Ocular examination, including ophthalmoscopy, is not shown on this Screenshot and was within normal limits. For key see Figure 1; SCBU, special care baby unit; EP, educational psychologist

Caption: Figure 7 Functional tests of Case 3. The 'presenting complaint' box overflowed, and the complete text is reproduced above the screenshot of the computerised main record. Ocular examination is described in the text. For key see Figure 1; www, internet; ST, sight test; FS, Mallett foveal suppression test; Fus Res, fusionai reserves

Caption: Figure 8. OCT scans for C4
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Title Annotation:Learning difficulties
Author:Evans, Bruce
Publication:Optometry Today
Date:Sep 1, 2018
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