2008 Abstracts
British and Irish Orthoptic Journal 2008
Editorial: A new section for the British and Irish Orthoptic Journal: Letter to the Editor/Clinical Report: Sarah J Shea
Research in Binocular Vision and Amblyopia: Recent Progress and Future Challenges
Frank Sengpiel
Aim: To review recent advances in our knowledge about the primary visual cortex and animal models of amblyopia and discuss their relevance for current treatment strategies and speculate about alternative future methods.
Methods: a literature-based review to highlight recent progress and future challenges in research in Binocular Vision and Amblyopia.
Results: Amblyopia is the most common developmental disorder of vision, resulting from abnormal visual experience during a critical period early in life. It is associated with physiological and anatomical changes (plasticity) in the primary visual cortex, which are deemed largely irreversible in adulthood. The classical animal model of amblyopia is monocular deprivation (MD) by eyelid suture, but induced or naturally occurring strabismus has also been studied extensively. In recent years, research has concentrated on understanding the neural mechanisms of binocular integration and of cortical plasticity during the critical period, as well as on exploring new avenues for extending plasticity into adulthood. Three lines of animal research are presented. First, the optimisation of eye-patching regimens to achieve the best possible visual acuity in both eyes, second, the neurophysiology of strabismic suppression, and third, new strategies for treating amblyopia in adolescents and adults, by means of either visual training paradigms or drug therapies aimed at restoring cortical plasticity after the end of the critical period.
Conclusions: The results of the research both complement clinical experience and provide a hopeful outlook for improved or novel methods of treating amblyopia in the future.
Impairment of Vision in Children due to damage to the brain - a practical approach
Elisabeth McKillop and Gordon N Dutton
Aim: To describe the visual problems, which children with brain damage may experience and to describe approaches to these, applicable to everyday life.
Methods: a literature-based essay using relevant articles and practical experience.
Results: Damage to the brain can affect both visual input and visual processing. Degradation of visual input results in reduced visual acuity, reduced contrast sensitivity and restricted visual fields. The dorsal stream passes between the occipital cortex and the posterior parietal lobes, which serve the ability to extract visual data from a complex scene, visual attention and the visual guidance of movement. The ventral stream passes between the occipital lobes and the temporal lobes and is responsible for recognition of what is being looked at and orientation. Any of these visual functions can be impaired to any degree and in any combination. Structured history taking and clinical examination is required to fully characterise the visual problems in each affected child in order to devise a tailored management strategy matched to the child’s needs.
Conclusions: Structured history taking and clinical examination in children with visual impairment secondary to brain damage can allow management to be customised to the individual requirements of that child.
Hypermetropia in childhood – a review of research relating to clinical management
Anna R O’Connor
Aims: There are numerous questions regarding the management of children with hypermetropia, such as what level of hypermetropia should be prescribed. The aim of this review is to evaluate the findings reported in the literature and to determine the areas where further research is required.
Methods: A literature search of databases was performed, focussing on publications from the last 10 years.
Results: The reported prevalence of hypermetropia in children ranges from 0.9 to 12.8%, depending on the age at test and definition of hypermetropia. There is no consensus on when to prescribe for hypermetropia but there is evidence to suggest that early correction results in fewer cases of amblyopia and strabismus. In addition hypermetropia has been shown to be associated with poorer reading and writing skills. The process of emmetropisation is affected by a number of factors, including preterm birth and strabismus, but the pattern of eye growth varies according to the type of strabismus present. Results of refractive surgery have been very successful only in relatively low degrees of hypermetropia.
Conclusion: Although there is considerable variation in the opinion on when to prescribe, the evidence suggests that early identification and correction of hypermetropia of 4 dioptres or above is probably beneficial by preventing cases of amblyopia and strabismus, and improving performance in many areas of development. There is still debate concerning the correction of lower amounts of hypermetropia and on the optimum method of identification and treatment.
The spectrum of nystagmus following cerebro-vascular accident
Fiona J Rowe
Aim: The purpose of this paper is to report the features of nystagmus documented following a confirmed diagnosis of cerebro-vascular accident (stroke).
Methods: Multi-centre prospective observational study undertaken in 14 acute Trust hospitals. Stroke survivors with suspected visual difficulty were recruited. Standardised screening/referral forms and investigation forms were employed to document data on visual impairment specifically assessment of visual acuity, ocular pathology, eye alignment and movement, visual perception (including inattention) and visual field defects.
Results: Of 323 patients, 38 were found to have nystagmus following cortical, brain stem or cerebellar stroke. Twenty were male and 18 female with a mean age of 65 years. Acquired nystagmus accounted for 84% of the types documented. Four patients had oscillopsia and three had vertigo. Associated ocular motility deficits were found in 84% of patients and treatment was largely aimed at alleviating diplopia but also reading difficulties or blurred vision. Improvement was noted in 42%.
Conclusions: 12% of stroke survivors with suspected visual difficulties had nystagmus documented. Most had associated ocular motility defects. Symptoms relating to the nystagmus of oscillopsia and vertigo were reported in 18%. Improvement of ocular motility was recorded in 42%.
Ultraviolet Radiation and Age-Related Macular Degeneration: The Protective Benefit of Blue-Light Blocking Intraocular Lenses: A literature review.
Catherine Howard and Fiona J. Rowe
Aim: To evaluate the association between ocular sunlight exposure and the risk of age-related macular degeneration. To explore the retinal protection offered by blue-light filters in ultra violet (UV) IOLs.
Methods: A literature search was undertaken using “Pub Med” and “Web of Knowledge” databases. Non-English language studies were not included. The review considers the effect of ultra-violet light on the eye with particular attention to retinal effects and age-related macular degeneration. The blue-light hazard is considered including the concept of blue-light filters in IOLs.
Results: The majority of papers did not find any statistical significance between sunlight exposure and ARMD. However, there were some statistically significant relationships between sunlight and early ARMD. Blue light has caused photochemical retinal damage in animal studies. Therefore, the presence of blue-light filters in IOLs may be indicated. Although theoretical predictions suggest a decrease in scotopic sensitivity with blue-light filter IOLs, clinical studies did not replicate these findings.
Conclusion: A causal association between ocular exposure to sunlight and the development of ARMD cannot be established from current literature. More epidemiological research is required to ascertain any strong association between sunlight exposure and ARMD, and to explore the effectiveness of UV and violet radiation filtering IOLs.
The relationship between Ophthalmic deficits and functional ability in low birth weight children
Vicki Wong; Anna R O’Connor; David Newsham; Paul C Knox and David Clark
Aims: To review the current literature on long term ophthalmic deficits and behavioural and/or cognitive outcomes occurring in low birth weight (LBW) children and to determine whether there is any link between the ophthalmic deficits and functional outcome.
Methods: A literature search was performed focusing mainly on publications from the past 10 years.
Results: LBW children are at an increased risk of a large number of ophthalmic deficits, including reduced visual functions (acuity, visual field, colour vision, stereoacuity and contrast sensitivity), increased prevalence of strabismus and all types of refractive error. These deficits are not isolated to the smallest children, they can occur with increased frequency in all LBW children. As a group LBWs have increased risk of cognitive and behavioural deficits, which can affect them throughout their education. There is evidence of an association between ophthalmic outcome and many aspects of functional ability (e.g. IQ, reading ability). Further research is required to discover if there is a common aetiology.
Conclusion: The evidence discussed supports the need for long term ophthalmic monitoring, and treatment where necessary, due to the potential impact on education and development. Currently there is no standardised approach for this. Further discussion is required to optimise long term care of all low birth weight children.
Normative Percentage Score for the Field of Binocular Single Vision
Kate Shotton; Teresa Smith; Ian Corbett and Nick Strong
Aim: To establish the mean value for the field of Binocular Single Vision (BSV) on the Goldmann perimeter in a visually normal population.
Methods: This was a prospective study on a visually normal, asymptomatic population. 119 participants completed the study. The field of BSV was evaluated using the III4e target on the Goldmann perimeter, and scored using the Sullivan template. Sub group analysis was performed according to age to assess for age related changes to the score.
Results: A score of 100% was rarely recorded for the participants. The overall population mean score was 94.43% (SD 4.25%; median 94.00%). One-way ANOVA test revealed a statistically significant reduction in the field of BSV with increasing age (p = 0.000). Correlation testing was performed (Pearson rank correlation r = -0.44).
Conclusions: Age related normal scores were produced and show strong evidence of a reduction in the field with increasing age.
A comparison of the concordance of ophthalmic outcome between low birth weight singletons and twins
Anna R O’Connor and Alistair R Fielder
Aims: The aims of this project were to determine whether low birth weight twins have a similar outcome, and to compare the outcome of the twins to a matched comparison group of low birth weight singletons
Methods: From a low birth weight (LBW) cohort (<1701g) of 572 infants there were 62 twin pairs (n=124). Of the 293 who were traced and consented to assessment at 10-12 years of age there were 34 twin pairs (n=68). From the remaining non twin LBW children a comparison group was created where the children were matched to each other based on birth weight, ethnicity, maternal smoking habits and whether they were small for their gestational age (neonatal group n=102, older group n=48). Ophthalmic assessment at 10-12 years included visual acuity, contrast sensitivity, evaluation of strabismus and refractive error.
Results: The twins showed a significant relationship with each other in terms of the presence or absence of retinopathy of prematurity (p=0.001, concordance=71%) but the matched singletons did not. The twin s had a statistically significant relationship in terms of the level of visual acuity and refractive error. However, the relationship between the refractive errors of the twins was weak (R2=0.14). The matched singleton group showed no statistically significant similarities on any measures of ophthalmic outcome. The level of concordance was higher between the pairs of twins for all measures of ophthalmic outcome compared to the matched singletons, but this increase did not reach statistical significance.
Conclusions: There was a higher rate of concordance in the twin children on all measures of visual outcome which suggests that when a deficits is detected in a low birth weight child from a multiple birth the sibling(s) should also be assessed. However, in this low birth weight cohort analysis compared to genetic factors, the degree of prematurity and the resultant systemic and ocular complications, have a greater impact on many measures of outcome.
Diagnostic accuracy of school vision screening
Catherine E. Stewart; James M. Gilchrist; Paul V. McGraw and Barry Winn
Aims: Currently, the Department of Health recommends vision screening of all children between the ages of 4 and 5 years. The aim of this study was to evaluate the diagnostic accuracy of entry-level school-aged vision screening in the UK. The performance of vision screening protocols and referral criterion (Snellen chart) has been compared with an alternative screening tool (Crowded logMAR test). Diagnostic accuracy has been modelled in terms of the screening test and referral criterion.
Methods: A total of 494 children (mean age 5.25 ± 0.28 yrs) were screened, for the presence of visual anomalies, by school nurses using a Snellen visual acuity chart and Crowded logMAR visual acuity test. Referral was made on the basis of Snellen visual acuity measures using standard NHS protocols (visual acuity 6/9 or worse).
Results: Within the population screened, approximately 14% (n=68) were referred for further investigation. Of the 68 children referred, over two-thirds were found to be visually normal (false-positive rate of 68%). No false-negatives were identified, indicating that the current screening criterion achieves maximum sensitivity. The Crowded logMAR test at the equivalent referral criteria (0.175 logMAR), also achieved maximum sensitivity but with significantly (p=0.0008) fewer false-positive referrals (60%).
Conclusion: Current school nurse screening criteria produce a high percentage of false-positives leading to low referral accuracy. However, current protocols provide maximum sensitivity (no false-negatives) for detecting visual anomalies. In order to retain maximum screening sensitivity whilst reducing the rate of false-positive referrals, screening programmes should adopt more precise measures of visual acuity in the form of logMAR-based tests.
The effect of coloured paper and lighting on the rate of reading in an adult student population.
Katy Naylor and Alison Y Firth
Aims: To investigate the effect of natural (1200Lux) and artificial lighting (450Lux) on the rate of reading from white and pink paper.
Method: Twenty university students were tested using the Wilkins rate of reading test (WRRT) reading text printed on both white and pink paper, in naturally and artificially lit conditions. The illumination levels were 1200Lux in the naturally lit room and 450Lux in the artificially lit room. The WRRT result was scored as mean number of words correctly read in one minute (wpm). Statistical data were analysed with repeated measures analysis of variance (ANOVA).
Results: Rate of reading was significantly quicker (p<0.01) when reading text printed on pink paper than when reading text printed on white paper. The mean increase was 5.17 words per minute. The rate of reading was also significantly faster (p<0.01) under the artificial (450Lux) lighting condition than the natural (1200Lux) lighting condition. The mean increase was 4.62 words per minute.
Conclusion: It was concluded that reading from pink paper and reading under lighting conditions with an illuminated level of 450Lux enhanced reading speeds.
Cerebral malaria and the eyes: Development of appropriate testing protocols for children in the developing world
Anna R O’Connor; David Newsham and Paul C Knox
Aims: The aim of this pilot study was to determine the feasibility of a number of tests of visual function and oculomotor control in children tested in Malawi.
Methods: Using computerised vision testing software, run on a laptop (Test Chart 2000 Pro), monocular visual acuity (VA) and contrast sensitivity (CS), using Lea symbols, were measured. Binocularity was assessed by the cover test and TNO, with assessment of ocular movements in 9 positions of gaze. Visual fields were assessed with a campimetry test run on the laptop. Antisaccade directional error rates were calculated from digital video recordings of eye movements.
Results: Seven subjects with a history of Cerebral Malaria (CM) and 13 healthy controls were recruited. All the tests were successfully employed in the majority of subjects although the antisaccade task was difficult for children under the age of 6 years. There was a trend to lower VA and CS in the CM subjects compared to controls. There were no cases of strabismus in either group; a slightly higher number of targets were missed on the visual field analysis in the CM subjects. The antisaccade directional error rates were inversely related to age showing the normal developmental trajectory.
Conclusions: The combination of tests used proved a useful and practical means of investigating visual function, binocularity and visuomotor development in children in the developing world
Letters to the Editor
Convergence Accommodation and Distance Exotropia.
Alison Y Firth
Summary: Convergence accommodation (that is the accommodation produced when the eyes converge) is a probable mechanism for the reduced binocular visual acuity seen in patients who control distance exotropia. Minus lens therapy may be advantageous to these patients and is a therapy that may benefit patients who do not demonstrate a high AC/A ratio.
Orthoptists Providing a Cost Effective Alternative Glaucoma Service
Karen Philips DBO, Orthoptist, Princess of Wales Hospital, Bridgend
Summary: With a short period of in-house training and a small increase in staffing levels, the orthoptists have established a glaucoma service, which has brought about the reduction of waiting times of new referrals to under 12 weeks and care of review cases. This service has significant benefits to the patients and is cost effective. As experienced decision making clinicians within the hospital eye care team orthoptists are well placed to participate in glaucoma care at a high level.
Vision screening- a benchmarking audit
R.McNamara
Summary: A benchmarking exercise carried out in 2006 found that despite the recommendations for an orthoptist-led vision screening service1-5 many primary care trusts were not providing comprehensive vision screening (vision testing of every child of one age group). Where screening is carried out it is not always orthoptist led and tests may be performed by health visitors, school nurses and school nurse assistants. Selective testing (testing a proportion of an age group using risk criteria) is being organised by health promotion groups and school health advisors rather than clinicians. The assessments vary from questions to identify children at risk6 to the recommended crowded logMAR letters test but many children are being tested with single optotype pictures or letters. The exercise highlighted the inequality of access to screening for children from neighbouring Primary Care Trusts (PCTs) and in London it was generally the most deprived areas with the greatest health needs, which had the least provision.
A Surviving Pre-School Vision Screening Service
M.Cross BSc (Hons), DBO
Summary: A pre-school screening programme that operates in south Derbyshire is described. Its advantages and disadvantages are discussed.