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Bruce J W Evans

Publications and source records attributed to Bruce J W Evans.

At least 19 recordsLinked to original sources

Orthoptic indications for contact lens wear.

Orthoptic anomalies are prevalent: they are encountered in at least 5% of patients seen in a typical primary eyecare practice. Several cases are reviewed that highlight the role of contact lenses in treating orthoptic anomalies. In particular, contact lenses are the preferred optical approach to the correction of anisometropia, and it is often argued that anisometropia should be corrected as young as possible. However, fitting contact lenses to patients, particularly children, with anisometropic amblyopia has been problematic because there is no immediate binocular acuity improvement when the contact lenses are inserted which reduces patient motivation. Continuous wear with silicone hydrogels represents a breakthrough for these cases and some illustrative case studies are given. The visual deficit in amblyopia can be reduced in some cases solely by fitting contact lenses, without the need for occlusion therapy. Other orthoptic uses of contact lenses are reviewed including: correcting motor deviations, occlusion, and infantile onset nystagmus. It is concluded that there are orthoptic anomalies where contact lenses are the preferred mode of correction. It is in patients' best interest for practitioners to discuss contact lenses in these cases.

Amblyopia↗

A clinical evaluation of Systane.

BACKGROUND: Systane is a new artificial tear solution containing the pH dependent gelling polymer hydroxypropyl-Guar (HP-Guar). We evaluated Systane in an open trial. METHODS: Patients complaining of dry feeling eyes were eligible to enroll, with inclusion criteria based on the presence of corneal staining with sodium fluorescein (NaFl) and participants' desire to use ocular lubricants. Six symptoms of ocular irritation were rated on a four-point scale. Conjunctival injection, conjunctival and corneal fluorescein staining were graded and tear break-up time (TBUT) and tear meniscus height were measured. Subjects were instructed to instill one drop of Systane into each eye four times a day for approximately four weeks. Ocular symptoms and signs were then reassessed and subjects were asked to rate eight statements concerning their satisfaction with the product. RESULTS: A total of 38 subjects were enrolled with 32 completing the follow-up visit. The following variables improved significantly at follow-up: all ocular irritation symptom scores, conjunctival injection, total conjunctival and total corneal staining scores, and TBUT. Tear meniscus height showed no significant change. Systane proved effective in reducing the symptoms of dry eye; however induced blur appeared to be a complication for many participants. CONCLUSIONS: The study represents a community based evaluation of the benefits of a novel ocular lubricant in optometric practice. The results suggest that the gelling properties of HP-Guar may be influential in promoting ocular surface recovery through improved ocular surface retention, however further randomised controlled trials are needed to confirm this. The extent and significance of induced blur also needs further investigation.

Adult↗

The correlation between migraine headache and refractive errors.

PURPOSE: A literature review reveals historical references to an association between migraine headache and refractive errors, but a lack of scientific evidence relating to these claims. METHODS: In a masked case-controlled study, we investigated the four aspects of refractive errors that have been implicated in the literature as correlated with migraine: spherical refractive error, astigmatic refractive error, anisometropia, and uncorrected ametropia. We also compared the calculated scalar value of refractive error, aided and unaided visual acuity, and spectacle use in migraine and control groups. We then investigated the relationship between refractive components and key migraine headache variables. RESULTS: Compared with the control group, the migraine group had higher degrees of astigmatic components of refractive error assessed both objectively (C, p = 0.01; C(0), p = 0.01; C(45), p = 0.05) and subjectively (C, p = 0.03; C(0), p = 0.03; C(45), p = 0.05), uncorrected astigmatic components of refractive error (C(0), p = 0.02; C(45), p = 0.04), and anisometropia (p = 0.06). CONCLUSIONS: Perhaps the historical literature is indeed correct that low degrees of astigmatism and anisometropia are relevant in migraine. Our most significant finding was of higher degrees of astigmatism in the migraine group. This study does indicate that people who experience migraine headaches should attend their optometrist regularly to ensure that their refractive errors are appropriately corrected.

Adult↗

The Mallett Fixation Disparity Test: influence of test instructions and relationship with symptoms.

Fixation disparity is a minute ocular misalignment under conditions of binocular single vision and is typically detected in primary eye care practices in the UK using the Mallett Unit Fixation Disparity Test. This instrument creates natural viewing conditions, when the patient's binocular system is fused using both central and peripheral fusion locks. This allows the examiner to determine the minimum prism power that eliminates the fixation disparity: the associated phoria or aligning prism. The spherical power that eliminates the fixation disparity, the aligning sphere, can also be determined. The near Mallett Unit Fixation Disparity Test has been shown to have good sensitivity and specificity for detecting symptomatic heterophoria. Cases of decompensated heterophoria tend to have a fixation disparity and the aligning prism or aligning sphere is a good indicator of the correction that will render the heterophoria compensated. The purpose of this study was, for the first time, to investigate the effect of test instructions on the results of the Mallett Unit Fixation Disparity Test. In study 1, we surveyed and observed practitioners to determine the instructions that are typically used. In study 2, we compared results obtained with this "standard" method of questioning with a more "specific" form of questioning that has been suggested in the literature. The participants for study 2 were 105 patients aged 7-70 years who were randomly selected from those attending a community optometric practice. Significantly different results were obtained with the two sets of instructions. The specific form of questioning revealed more cases of fixation disparity and the results with this method showed a better correlation with symptoms. This only held for near vision: for distance vision, symptoms were not significantly correlated with the presence of fixation disparity. This agrees with previous work with the Mallett unit, which showed a significant relationship with symptoms only at near. We also found that patients with more severe symptoms had greater degrees of aligning prism. Our study supports previous work indicating that the Mallett unit is a useful tool for detecting symptomatic heterophoria at near. However, we found that the testing method is important: patients need to be asked not just whether the nonius strips are aligned but also whether one or both of the strips ever moves. More research is needed to investigate the significance of precise test instructions in other optometric and orthoptic tests.

Adolescent↗

Double-masked randomised placebo-controlled trial of the effect of prismatic corrections on rate of reading and the relationship with symptoms.

Practitioners' decisions on when to intervene in decompensated heterophoria are often based on symptoms, which are in some cases an unreliable indicator of whether an intervention will be helpful. The aim of our study was to determine when prismatic corrections improve performance at a measure of dynamic visual function: the Wilkins Rate of Reading Test (WRRT). All participants manifested an aligning prism (associated heterophoria) on the near Mallett Unit of 0.5Delta or greater. There were 80 participants, of whom 58 had exophoria, 15 esophoria, and seven hyperphoria. The effect of the aligning prism on the WRRT was compared with a control lens using a double-masked randomised design. For exophoria, an aligning prism of 2Delta and above has a sensitivity of 67% and a specificity of 79% for improving performance at the WRRT by 5% or more. It is not possible from our data to achieve a good compromise between sensitivity and specificity for the other types of heterophoria. Patients in the horizontal (but not vertical) heterophoria groups had significantly more symptoms than a control group. The patients whose visual performance is improved by prismatic correction are not necessarily those who report the most symptoms. Our data suggest that exophoric patients of any age are likely to have improved visual performance with an intervention if they have an aligning prism of 2Delta or more, even in the absence of symptoms. We stress that although the Mallett Unit Fixation Disparity test provides useful information, its results need to be considered in the overall context of the patient's symptoms, lifestyle, and the results of other optometric tests. Although this study evaluated prismatic corrections, we note that interventions for decompensated heterophoria include not only prismatic corrections, but also eye exercises and refractive modification.

Adaptation, Ocular↗

Subtle binocular vision anomalies in migraine.

A literature review reveals old references to an association between migraine headache and binocular vision anomalies, but a lack of scientific evidence evaluating these claims. In a masked case control study, we investigated binocular vision using standard clinical tests in people with migraine and in controls. Some test results suggest that heterophoria and fixation disparity are more common in the migraine group. The migraine group also had slightly reduced stereopsis. We found significant correlations between some migraine variables and some binocular vision variables (e.g., duration of worst headache and impaired stereopsis) but our analyses do not suggest that a causal relationship is likely. In conclusion, people with migraine have on average a slightly higher prevalence of heterophoria and aligning prism, and reduced stereopsis compared with controls. However, the differences are subtle and our data do not support the use of binocular vision interventions prescribed solely on the basis of the presence of migraine.

Adult↗

Visual stimuli are common triggers of migraine and are associated with pattern glare.

OBJECTIVE: To investigate the associations between interictal pattern glare, visual stress, and visual triggers of migraine. BACKGROUND: There has been relatively little research on the visual stimuli that can trigger migraine episodes. This is surprising, since if practitioners can obviate such triggers, then some attacks may be prevented. The existing literature suggests that patients who are prone to visually triggered migraines report more illusions on viewing striped patterns ("pattern glare") and that colored filters may be an effective intervention for these people. METHODS: Headache symptoms and headache triggers were investigated in migraine and control groups in 2 separate experiments. In one experiment, we also determined, for each participant, pattern glare, whether it was reduced by colored filters and, if so, what the optimum color of filter was. Color vision was also assessed with the D15 test. RESULTS: People with migraine saw significantly more illusions on viewing each striped pattern and experienced greater pattern glare. They were also more likely to select a colored filter to aid visual comfort, particularly colors in the blue-to-green sector of the spectrum. Color vision was impaired subtly but significantly in migraine. Principal component analyses grouped common headache triggers into 5 broadly equal components: food, visual triggers, alcohol, stress and tiredness, and the environment. In a second analysis, the overall number of illusions seen in striped patterns was associated with visual triggers while pattern glare, use of colored filters, and interictal light sensitivity together formed a sixth component interpreted as visual stress. CONCLUSIONS: It is suggested that clinicians should ask migraine patients whether visual stimuli trigger their migraine, about interictal visual symptoms, and use the pattern glare test to ensure that those who may benefit from optometric interventions are appropriately managed.

Acute Disease↗

Frequency doubling technology perimetry and standard automated perimetry in migraine.

The literature suggests that visual field defects may be more common in people who experience migraine. The Humphrey frequency doubling (FDT) visual field instrument selectively examines the magnocellular visual pathway, but has not previously been used to investigate visual function in migraine. In a masked controlled study we compared Humphrey FDT and Humphrey Swedish Interactive Threshold Algorithm fields of 25 migraine sufferers with 25 age- and gender-matched controls. Although both mean deviation and pattern standard deviation were a little worse in the migraine group, these differences did not reach statistical significance. There were no inter-eye visual field differences in the migraine group compared with controls. Comparing the mean of all the contrast thresholds in each hemisphere, there were no more inter-hemifield visual field differences in the migraine group compared with controls. There was no significant difference between the migraine and control groups in intra-ocular pressures. The visual field parameters were not correlated with the interval since the last migraine headache, the severity of migraine headache, the duration of migraine headache or the number of migraine headaches per annum. In our data, there was no evidence of visual field deficits, a magnocellular deficit, or indications of glaucomatous pathology.

Adolescent↗

The need for optometric investigation in suspected Meares-Irlen syndrome or visual stress.

Meares-Irlen syndrome is characterised by symptoms of eye strain, headaches and visual perceptual distortions when viewing text. The symptoms are alleviated with individually prescribed coloured filters, such as precision tinted lenses. Meares-Irlen syndrome, and the related condition of visual stress, are likely to result from hyperexcitability of the visual cortex, which can also occur in migraine. The symptoms of Meares-Irlen syndrome and visual stress are non-specific and the condition needs to be differentially diagnosed from other optometric conditions, such as refractive error, binocular vision anomalies, and accommodative anomalies. Three case reports are described of patients who consulted the author with suspected Meares-Irlen syndrome but were found to have other causes for their symptoms: posterior sub-capsular cataract, high uncorrected astigmatism, and decompensated convergence weakness exophoria. These cases highlight the need for professional eye care for people with suspected Meares-Irlen syndrome. Although this advice is stressed in literature on the well-established MRC/Wilkins Intuitive Colorimeter system, it is not always stressed in literature about other systems. This may be a cause for concern.

Adult↗

The pupillary light reflex in migraine.

The literature suggests that there may be pupil size and response abnormalities in migraine headache sufferers. We used an infra-red pupillometer to measure dynamic pupil responses to light in 20 migraine sufferers (during non-headache periods) and 16 non-migraine age and gender matched controls. There was a significant increase in the absolute inter-ocular difference of the latency of the pupil light response in the migraine group compared with the controls (0.062 s vs 0.025 s, p = 0.014). There was also a significant correlation between anisocoria and lateralisation of headache such that migraine sufferers with a habitual head pain side have more anisocoria (r = 0.59, p < 0.01), but this was not related to headache laterality. The pupil changes were not correlated with the interval since the last migraine headache, the severity of migraine headache or the number of migraine headaches per annum. We conclude that subtle sympathetic and parasympathetic pupil abnormalities persist in the inter-ictal phase of migraine.

Adult↗

Effect of light filters on reading speed in normal and low vision due to age-related macular degeneration.

PURPOSE: To investigate the effects of light filters on reading speed in normal and low vision due to age-related macular degeneration (AMD). METHODS: Reading speed was determined for 12 subjects with normal vision and 12 subjects with non-exudative AMD using stationary lowercase nonsensical print in Times Roman font and four light filters; a yellow Corning Photochromic Filter (CPF) 450, a grey neural density (ND) filter, an individual filter obtained using the Intuitive Colorimeter and a clear filter. RESULTS: There was no statistically significant light filter effect on reading speed for the normal subjects. The AMD group demonstrated a statistically significant 5% average improvement in reading speed with the CPF450 compared with the other filters although some AMD subjects had improvements of 10-15%. CONCLUSIONS: Light filters obtained using the Intuitive Colorimeter(R) performed poorly when compared with the CPF450, ND and clear filters for both the study groups. For the AMD group, average reading speed was statistically greater with the CPF450 than the other filters, however it is questionable whether the improvement (5%) would be clinically significant. As some of the subjects with AMD had greater improvements with the CPF450 we advocate clinical assessment of light filters using existing protocols on an individual basis.

Aged↗

Correctable visual impairment in older people: a major unmet need.

This review seeks to determine the prevalence of correctable visual impairment (VI) in older people in the UK, to discover what proportion of these cases are undetected, to suggest reasons for the poor detection and to make recommendations for improving the detection. To establish the context of these issues, the review will also touch on the general prevalence and causes of VI in older people in developed countries and on the impact of VI in older people. Typically, studies suggest that VI affects about 10% of people aged 65-75, and 20% of those aged 75 or older. There is a strong relationship between impaired vision in older people and both reduced quality of life and increased risk of accidents, particularly falls. The literature suggests that those with low vision are about two times more likely to have falls than fully sighted people, and the annual UK cost of treating falls directly attributable to VI is pound 128 million. The literature on the prevalence of undetected reduced vision in older people reveals that between 20 and 50% of older people have undetected reduced vision. The majority of these people have correctable visual problems (refractive errors or cataract). It is particularly startling that, in 'developed countries', between 7 and 34% of older people have VI that could simply be cured by appropriate spectacles. The reasons why so many cases of treatable VI remain untreated are discussed, and suggestions are made for improving the detection of these cases. We conclude that there should be better publicity encouraging older people to attend for regular optometric eye examinations. A complementary approach is annual visual screening of the elderly, possibly as part of GPs annual health check on people aged 75 years and older. Recommendations are made for evaluating new approaches to screening and for improving the management of cases detected by screening.

Accidental Falls↗

The optometric correlates of migraine.

Migraine is a common, chronic, multi-factorial, neuro-vascular disorder typically characterised by recurrent attacks of unilateral, pulsating headache and autonomic nervous system dysfunction. Migraine may additionally be associated with aura; those focal neurological symptoms that may precede or sometimes accompany the headache. This review describes the optometric aspects of migraine headache. There have been claims of a relationship between migraine headaches and errors of refraction, binocular vision anomalies, pupil anomalies, visual field changes and pattern glare. The quality of the evidence for a relationship between errors of refraction and binocular vision and migraine is poor. The quality of the evidence to suggest a relationship between migraine headache and pupil anomalies, visual field defects and pattern glare is stronger. In particular the link between migraine headache and pattern glare is striking. The therapeutic use of precision-tinted spectacles to reduce pattern glare (visual stress) and to help some migraine sufferers is described.

Asthenopia↗

The effects of coloured light filter overlays on reading rates in age-related macular degeneration.

PURPOSE: To determine the effect of coloured light filter overlays on reading rates for people with age-related macular degeneration (AMD). METHOD: Using a prospective clinical trial design, we examined the null hypothesis that coloured light filter overlays do not improve reading rates in AMD when compared to a clear filter. Reading rates for 12 subjects with non-exudative AMD, associated with a relative scotoma and central fixation (mean age 81 years, SD 5.07 years) were determined using the Rate of Reading Test (printed, nonsense, lower case sans serif, stationary text) with 10 different, coloured light filter overlays (Intuitive Overlays); figures in brackets are percentage transmission values); rose (78%), pink (78%), purple (67%), aqua (81%), blue (74%), lime-green (86%), mint-green (85%), yellow (93%), orange (83%) and grey (71%). A clear overlay (Roscolene # 00) (360 cdm-2) with 100% transmittance was used as a control. RESULTS: Anova indicated that there was no statistically significant difference in reading rates with the coloured light filter overlays compared to the clear filter. Furthermore, chi-squared analysis indicated that the rose, purple and blue filters had a significantly poorer overall ranking in terms of reading rates compared to the other coloured and clear light filters. CONCLUSION: Coloured light filter overlays are unlikely to provide a clinically significant improvement in reading rates for people with non-exudative AMD associated with a relative scotoma and central fixation.

Aged↗

Criteria for prescribing optometric interventions: literature review and practitioner survey.

The core function of optometrists is the prescribing of refractive corrections, yet a literature review revealed a lack of evidence-based research on criteria for determining when a refractive correction is required. The reported criteria used by practising optometrists were investigated using a questionnaire to survey prescribing habits for borderline hypermetropia, presbyopia, astigmatism, and horizontal and vertical heterophoria. Thirty-eight questionnaires were returned and the results analysed. We calculated the 'cut off' point above which the anomaly would be corrected over 50% of the time that it was encountered. There was a large variation for each category, but it was clear that the presence or absence of symptoms was an important factor for most optometrists when deciding whether to correct a small error. It was found that for symptomatic patients, most optometrists would correct an anomaly if it reached: +1.00 D of hypermetropia, a reading addition of +0.75 D for presbyopia, -0.75 DC of astigmatism, 1.5 prism dioptres (Delta) of horizontal aligning prism, and 1 Delta of vertical dissociated heterophoria. For asymptomatic patients, optometrists would not correct any of the hypermetropic anomalies or heterophorias that were specified in our questionnaire. However most would correct a presbyopic error of +1.50 D or above, or an astigmatic error of -1.50 DC or above, even in the absence of symptoms. These results were compared with previously published guidelines.

Adult↗

Randomised controlled trial of the effect of coloured overlays on the rate of reading of people with specific learning difficulties.

A randomised controlled trial has demonstrated that, for selected children with reading difficulties, individually prescribed coloured filters reduce symptoms of asthenopia. In the present study, we investigate the effect of individually prescribed coloured overlays on the rate of reading. Subjects were 33 children and adults who: had consulted a specific learning difficulties clinic; had received treatment to normalise any conventional optometric and orthoptic anomalies; and subsequently reported symptomatic relief from coloured filters. These subjects carried out the Wilkins Rate of Reading Test (which assesses visual rather than linguistic factors) under two conditions: with their chosen coloured overlay and with a control filter. Steps were taken to ensure that a strong placebo effect was associated with the control overlay and, when asked which they preferred, subjects were not significantly more likely to prefer their coloured overlay than the control filter (p=0.11). Nonetheless, the rate of reading was significantly faster with the coloured overlay than with the control (p=0.0019). Further analyses support the conclusion that individually prescribed coloured filters can improve reading performance for reasons that cannot be solely attributed to conventional optometric factors or to placebo effects.

Adult↗

Do tinted lenses or filters improve visual performance in low vision? A review of the literature.

This is a review of studies that have investigated the proposed rehabilitative benefit of tinted lenses and filters for people with low vision. Currently, eye care practitioners have to rely on marketing literature and anecdotal reports from users when making recommendations for tinted lens or filter use in low vision. Our main aim was to locate a prescribing protocol that was scientifically based and could assist low vision specialists with tinted lens prescribing decisions. We also wanted to determine if previous work had found any tinted lens/task or tinted lens/ocular condition relationships, i.e. were certain tints or filters of use for specific tasks or for specific eye conditions. Another aim was to provide a review of previous research in order to stimulate new work using modern experimental designs. Past studies of tinted lenses and low vision have assessed effects on visual acuity (VA), grating acuity, contrast sensitivity (CS), visual field, adaptation time, glare, photophobia and TV viewing. Objective and subjective outcome measures have been used. However, very little objective evidence has been provided to support anecdotal reports of improvements in visual performance. Many studies are flawed in that they lack controls for investigator bias, and placebo, learning and fatigue effects. Therefore, the use of tinted lenses in low vision remains controversial and eye care practitioners will have to continue to rely on anecdotal evidence to assist them in their prescribing decisions. Suggestions for future research, avoiding some of these experimental shortcomings, are made.

Adaptation, Physiological↗