2009 Abstracts

British and Irish Orthoptic Journal 2009

Editorial: Thoughts from an editor’s diary: a six-year experience

Sarah J Shea

Multiple sclerosis: diagnositic issues and modern management.

Siân E Price

Aims: To provide an insight into the current issues in the diagnosis and management of Multiple Sclerosis (MS).

Methods: A literature-based review was undertaken to determine diagnostic criteria, differential diagnosis, and the use of disease modifying medication and symptomatic treatments for MS. The main source of references was Medline via Pub Med but standard major reference works on MS were also used.

Results: The prevalence of MS may be increasing, especially in women, thereby increasing the need for resources for diagnosis and clinical management of the condition. Clinical diagnosis of MS has changed little since the descriptions of Charcot. However new diagnostic techniques ranging from neurophysiology and spinal fluid analysis to increasingly sophisticated magnetic resonance imaging, have allowed the condition to be diagnosed earlier and with more confidence. New insights in immunology and neuropathology allow differential diagnoses to be excluded and continue to lead to different approaches to managing the condition. New disease modifying drugs are being used, with the realistic hope of altering the progression of disability. Equally as important are new techniques and medications aimed at symptom management, ranging from multi-disciplinary team working to drug treatment of pain, fatigue, spasticity, continence, and nystagmus.

Conclusions: There is continuing improvement in many aspects of the care of people with MS. Insights from epidemiology, genetics, pathology, and clinical trials have all contributed to this.

Screening for amblyopia and strabismus in children aged 4-5 years: where do we go from here?

Jill Carlton and Carolyn Czoski-Murray

Aim: To describe the history of vision screening for amblyopia and strabismus and identify knowledge gaps within the literature.

Method: A review of the literature is presented which includes an examination of screening guidelines.

Results: A recent Health Technology Appraisal reported that screening for amblyopia and amblyogenic factors was not cost-effective, and highlighted a need for further research into the impact of amblyopia and amblyogenic factors in the long-term. Despite recommendations to the contrary vision screening varies in content across the United Kingdom (UK), particularly with respect to personnel undertaking the screening tests.

Conclusion: Uncertainty surrounding the appropriateness of vision screening remains, with areas of the literature still lacking in evidence to support screening programmes. Debate is needed as to the strategic approach of the orthoptic profession in the application of vision screening across the UK.

Visual neglect: should we attend to it?

Tracey L Shipman

Aim: To review the literature on unilateral visuo-spatial inattention/neglect following stroke, concentrating on the areas of the brain involved, methods of assessment and therapeutic options.

Methods: A literature-based essay was conducted using relevant articles and practical experience to elicit current theories of inattention and to discover whether any evidence-based treatment strategies exist. As there are numerous testing approaches for inattention, evidence was also sought for the most appropriate and accurate assessment tool(s).

Results: The Star cancellation, line bisection and random shape cancellation tests appeared to be the most sensitive for detecting neglect; however a range of tests is necessary in order to detect severity. Therapeutic options may include scanning techniques and visuo-motor cueing into the affected side, prism adaptation and limb activation to increase awareness of the affected side and reduce inhibition by the healthy hemisphere. Motor and functional recovery of stroke patients with neglect seems to be improved by targeted treatment.

Conclusion: Neglect is an important predictor of poor functional recovery and therefore treatment remains a high priority. More research, however, is needed to better define which treatment options are the most effective.

Management of nystagmus by surgery and botulinum toxin options: A review

Fay Hobson and Fiona J. Rowe

Aim: To critically evaluate the literature in order to explore the success of botulinum toxin and extra ocular muscle surgery in the management of acquired nystagmus.

Methods: A literature search was undertaken using “Pub Med” and “Web of Knowledge” databases. Non-English language studies were not included.

Results: The aim of using botulinum toxin is to alleviate the symptoms induced by acquired nystagmus. The major problematic symptoms are oscillopsia, reduced visual acuity and abnormal head posture. An injection of botulinum toxin into the retrobulbar space is beneficial if the acquired nystagmus has horizontal, vertical and torsional components, whereas if the nystagmus is purely horizontal an injection of botulinum toxin into the horizontal rectus muscles appears to be the better option. Surgery undertaken is aimed at alleviating the symptoms induced by acquired nystagmus. Extra ocular muscle surgery is of value in the management of acquired nystagmus particularly if the patient has developed an abnormal head posture.

Conclusion: It is difficult to come to any clear-cut conclusions due to the low numbers of patients that have been studied. It would, however, appear that botulinum toxin and surgery are of some value in the management of acquired nystagmus. Further research is required in this area.

Grapheme-colour synaesthesia and the orthoptist

Marianne E. F. Piano¹ BSc (Hons), Paul C. Knox² PhD, Anna O’Connor

Aim: To give an overview of the condition known as colour-grapheme synaesthesia, and examine whether there is a need for orthoptists to be aware of its existence and potential impact when co-existing with other conditions, such as specific learning difficulty and Meares Irlen Syndrome.

Methods: A literature-based review was performed. Relevant material was identified using the University of Liverpool library catalogue, Google, Pubmed and Web of Knowledge. The focus was on relevant research published within the last fifteen years.

Results: Evaluation of the literature shows that colour-grapheme synaesthesia is thought to arise from increased structural connectivity between brain areas involved in the processing of colour and visual word forms. The colour-grapheme linkages are very specific and long-standing, possibly congenital, and the condition is probably genetic. It is more common than previously thought, and could potentially co-exist with other visual perceptual difficulties such as dyslexia and Meares Irlen Syndrome. However, due to a lack of awareness of the condition it is rarely diagnosed. As grapheme-colour synaesthesia appears to have an impact on reading and mathematical ability, it is relevant to the orthoptist’s extended role in assessing children with these conditions.

Conclusion: Colour-grapheme synaesthesia is more common than previously thought, and although more research is needed to establish the true impact of grapheme-colour synaesthesia on other visual conditions, the orthoptist may wish to consider including the condition in the list of differential diagnoses in cases of specific learning difficulty and Meares-Irlen Syndrome.

Ocular motility consequences following lesions of the thalamus: a literature review

Elinor Jones and Fiona J. Rowe

Aim: To summarise the anatomy and function of the thalamus and review the medical literature for types of thalamic lesions and resultant ocular motility deficits.

Methods: A literature search was undertaken using “Pub Med” and “Web of Knowledge” databases. Non-English language studies were not included.

Results: Types of thalamic lesions included vascular infarct or haemorrhage, space occupying lesions, birth trauma, and associated periventricular leukomalacia. Ocular motility deficits included vertical gaze palsies, skew deviation, convergence anomalies, third nerve palsy, nystagmus, pupil and lid anomalies, plus saccadic and smooth pursuit deficits.

Conclusion: Vascular pathology is most common in causing thalamic lesions and may be partial or complete unilateral lesions or bilateral. The predominant ocular motility deficit reported is that of vertical gaze palsy. Commonly involvement of the midbrain also occurs.

A comparative review of methods to record ocular rotations

Sahira Hanif; Fiona Rowe and Anna O’Connor

Aim: To review the methods reported for recording ocular rotations.

Methods: A literature-based review from 1899 to 2008 was carried out to enable a comparative discussion on the methods available to record ocular rotations.

Results: The recording of ocular rotations has changed and progressed over the years. Different methods are available that are kinetic or static methods. The important factors in evaluating the efficacy of methods for recording ocular rotations are, minimising patient discomfort; maintaining accuracy and minimising variability from head and chin movement; the speed and simplicity of the test, particularly for elderly patients; good repeatability and level of inter- and intra-observer reliability.

Conclusion: No one method has been advocated in the literature as the gold standard. However, clinically the Goldmann perimeter for kinetic recording and the Lees screen for static recording are popular.

The effect of artificially reduced bilateral visual acuity on vergence adaptation.

Pooja S Bhatt and Alison Y Firth

Aims: To investigate the effect of bilateral artificially reduced vision on vergence adaptation, in participants with normal binocular Single Vision (BSV).

Methods: Seventeen participants were recruited from a student population. The inclusion criteria included the ability to adapt to a 6Δ base-out prism to within ±1Δ of the baseline heterophoria measurement in 10 minutes. The size of the prism-induced heterophoria was measured at the start and end of the adaptation period using a Maddox rod and tangent scale. Eleven participants fitted the inclusion criteria and proceeded to a second visit; involving adaptation to a 6Δ base-out prism within 10 minutes, whilst vision was bilaterally reduced with Bangerter foils (0.3). Participants who did not demonstrate adaptation to within ±1Δ of the baseline measure in 10 minutes, were given a further 10 minutes to adapt, with the size of the residual deviation being measured at 5 minute intervals.

Results: Eight out of eleven participants demonstrated vergence adaptation to within ±1Δ of the baseline measure in 10 minutes when vision was bilaterally reduced. Three participants required an additional 5 minutes before they achieved this level of adaptation. Statistical analysis revealed the rate of vergence adaptation was affected in some participants when vision was bilaterally reduced (p=0.0260, t=2.6116, d.f=10).

Conclusion: Individuals who demonstrate vergence adaptation in normal viewing conditions appear capable of doing this with an artificial bilateral reduction in vision. In some participants, a longer period of time is required to vergence adapt.

Does fixation light intensity influence the results from the Sbisa bar when measuring sensory fusion?

Stephanie A Tate. MMedSci (Orthoptics) BMedSci (Orthoptics)¹; Carolyn Leach

Aim: To determine if the level of sensory fusion in normal participants is affected significantly by fixation light intensity.

Methods: Seventeen normal adult participants had sensory fusion measurements taken using the Sbisa bar, combined with Bagolini glasses as a control for binocular single vision, whilst fixating lights of three different intensities: 150 lux, 250 lux and 350 lux. Data were analysed using Friedman’s test and Wilcoxon matched pairs signed ranks test.

Results: Seventeen participants were tested (mean 35.3 years, range 23-60 years). Friedman’s test showed at least 2 of the light intensities had a statistically significant effect upon sensory fusion results (p=0.011). Wilcoxon matched pairs signed rank testing found, no statistically significant difference in levels of sensory fusion when fixating the 150 lux and 250 lux fixation lights (p=0.194). There was a statistically significant difference in the level of sensory fusion when fixating the 150 lux and 350 lux lights (p=0.011) and the 250 lux and 350 lux lights (p=0.017).

Conclusion: Changing the intensity of the fixation light from 150 lux to 350 lux and from 250 lux to 350 lux significantly affected the level of sensory fusion measured. The higher the intensity of the light, the greater the filter needed to break fusion. The clinical significance of these results is considered.

Convergence accommodation to convergence (CA/C) ratio: stability with different levels of convergence demand.

Komal J Hirani and Alison Y Firth

Aim: The aim of this study was to measure the convergence accommodation to convergence (CA/C) ratio over a range of levels of convergence demand.

Method: Convergence accommodation was measured in twenty six subjects with normal binocular single vision (BSV). The CA/C ratio was calculated by measuring the accommodative changes induced with base-out prisms of 5Δ to 20Δ in 5 Δ steps whilst the participant maintained binocular fixation on a pseudo- Gaussian target at 40cm. Accommodative change was measured using the open- field view Shin- Nippon SRW-5000 autorefractometer [Grand Seiko Company, Fukuyama, Japan].

Results: The mean age of the participants was 20 ± 2.5 years (range: 18 to 29 years).

The mean (± S.D.) CA/C ratio for the 5Δ, 10Δ, 15Δ and 20Δ was 0.13 (± 0.07) D/PD, 0.12 (± 0.05) D/PD, 0.13 (± 0.05) D/PD and 0.13 (± 0.05) D/PD respectively. The overall mean (±S.D.) CA/C ratio was 0.13 (± 0.04) D/PD (Range: 0.04-0.20 D/PD). One factor repeated measures ANOVA found that the CA/C ratio did not significantly change with an increase in convergence (F=0.202, d.f. =3, 69, p=0.8947).

Conclusion: The CA/C ratio did not significantly change with increasing induced vergence. The data suggest that some degree of nonlinearity / variation should be expected in the normal, healthy population of the same age group.

Is the prevalence and level of astigmatism different in indigenous Bangladeshi children compared to first generation children of Bangladeshi origin born in the United Kingdom?

Fatima Mangera

Aim: to compare the prevalence and level of astigmatism in indigenous Bangladeshi, first generation British-Bangladeshi and indigenous white British children.

Method: Indigenous Bangladeshi, first generation British-Bangladeshi and indigenous white British children, aged 6 – 10 years were recruited from within six London primary schools in the borough of Tower Hamlets. Each child’s refractive error was measured using the Plusoptix autorefractor without cycloplegia. Three readings were taken for each child and averaged to give the mean value for astigmatism.

Results: 138 (12.8%) positive responses were received in total. Of these, 80 (57%) children fulfilled the inclusion criteria. 58 (42%) children were rejected because full parental consent was not given for 15 children; 32 children did not fulfill the strict ethnic criteria of the study and 11 children were not within the age range of the study. Eighteen children who fulfilled the criteria were absent from school on the day of testing. In total 62 (45%) children were tested. Analysis showed there was no significant difference in the amount of astigmatism for the right eye (Chi-Square 2.306; df 2; p=0.316) or left eye (Chi-Square 2.935; df 2; p=0.231) across the three groups.

Conclusion: There was no significant difference in the amount of astigmatism for the right and left eye between indigenous Bangladeshi, first generation British-Bangladeshi and white-British children aged 6 - 10 years old. However due to the small number of children recruited there was limited power to detect any significant differences in the findings.

The Effect of Induced Vertical Divergence on Horizontal Fusional Amplitudes

Greg A Richardson and Alison Y Firth

Aim: To find out whether horizontal fusion was compromised in the presence of slight vertical deviations induced with small vertical prisms.

Methods: Eighteen fully binocular participants were recruited from a student population. Horizontal prism fusion range (PFR) was tested in the presence of 1Δ and 2Δ vertical prisms and with no vertical prism as a control. One eye remained occluded until horizontal fusion was to be tested to reduce the effects of vergence adaptation. Prism fusion range was measured to break point under each of the three conditions.

Results: As vertical divergence was increased, horizontal fusional amplitudes reduced (Friedman test: p<0.0001). Wilcoxon signed rank tests showed that differences were statistically significant between 0Δ and 2Δ of induced vertical divergence, and between 1Δ and 2Δ of induced vertical divergence. When no vertical divergence was induced the median PFR was 33∆ (interquartile range 15Δ), for 1∆ vertical, 30∆ (interquartile range 17Δ) and for 2∆ vertical, 22∆ (interquartile range 12Δ).

Conclusions: The greater the induced vertical divergence, the smaller the horizontal fusional amplitude recorded. This reduction was statistically significant with 2∆ of induced vertical divergence.

Pseudostrabismus secondary to macular heterotropia: A case report and literature review

Laura B. Wilkinson

Aim: To present a case of pseudo-strabismus secondary to macular heterotropia, caused by retinopathy of prematurity (ROP). An overview of literature on this subject is discussed.

Method: The case of a 9-year-old child born prematurely at 26 weeks gestation, who had cryotherapy treatment for Stage 3 ROP, is reported, with reference to birth history, ophthalmic, orthoptic and photographic findings.

Results: The patient had a pseudo-exotropia resulting from an abnormal shifting of the macula known as macular heterotropia, an abnormal fundus appearance found in ROP, especially in eyes treated with cryotherapy. Macular heterotropia has been reported in conditions such as retinal tear, idiopathic retinal folds, persistent hyaloid vessels, chorioretinal coloboma, chorioretinisis, Toxocara canis^, vitreous structural anomalies, and very high myopia.

Conclusions: Orthoptists should be aware of the features of macular heterotropia and associations with ROP and pseudo-strabismus.

Prevention of stimulus deprivation amblyopia in children with eyelid capillary haemangioma

Shahenna Hussain and Clare Dewsbery

Aim: To present a case of eyelid capillary haemangioma with complete eye closure in an infant.

Method: A case is discussed of a 5-week-old baby with eyelid capillary haemangioma. Ophthalmic and orthoptic findings are documented, with photographs. Investigation and treatment are described to illustrate the measures taken to prevent stimulus deprivation amblyopia of the affected eye.

Results: Due to rapid growth of the haemangioma there was complete eye closure with an inability to open the eye. Full time occlusion of the non-affected eye was commenced and combined with steroid treatment of the haemangioma. The haemangioma significantly reduced in size. At the age of 53 weeks, visual acuity appears equal and binocular vision responses are demonstrable.

Conclusion: Total occlusion of the good eye to prevent stimulus deprivation amblyopia of the affected eye is an option when methods of keeping the affected eye open have failed.

Letter to the Editor

Controlled Binocular Acuity (CBA).

Alison Y Firth and Helen H Davis

Summary: Controlled binocular acuity is defined and the reference for the reasons behind proposing the new term given.