2005 Abstracts
British and Irish Orthoptic Journal 2005 Volume 2
Vergence adaptation - a phenomenon of normal binocular vision.
Alison Y Firth
Aim: To describe vergence adaptation and how it may impact on clinical practice.
Method: A literature based essay is presented, which includes a review of published work over the last 7 years and older literature as appropriate.
Results: Vergence adaptation is a normal phenomenon which occurs in the presence of binocular single vision to induced concomitant and incomitant deviations. It may be affected by age and practice. It may mask larger deviations than those initially seen during clinical testing and may be of significance in the aetiology of some forms of strabismus.
Conclusion: Vergence adaptation has previously been acknowledged as being important in the maintainance of comfortable binocular vision. Consideration of the phenomenon is useful in explaining many observations seen during orthoptic practice.
Clinical assessment of stereopsis and its functional significance.
Hayley Morris; Anna R O'Connor; M Gail Stephenson; Maureen Mitchell; Gary J Price; Susan Anderson BSc
Aim: To review the efficacy of near and distance stereotests in current use and to question the functional benefits of stereopsis based on current evidence.
Method: A literature review was carried out to analyse the current reports of what is a normal level of stereopsis and how and why this varies according to the test used. In addition the role of stereopsis in many aspects of life is evaluated.
Results: The values reported for the normal limits of near stereoacuity vary greatly with only a weak correlation. Some of the variation can be attributed to test difficulties, such as monocular cues, or the population tested. There is no consensus as to whether near or distance stereoacuity are equal or vary and if so which is best. In terms of functional ability stereopsis has been shown to be beneficial in many areas such as academic ability, driving and sports.
Conclusions: The values reported for stereoacuity continue to pose questions with regards to the best approach for screening and clinical care. With tests now available to assess stereoacuity in the distance it is anticipated that knowledge of conditions, and subsequent treatment, will improve in conditions such as intermittent distance exotropia. In response to the question 'do we need stereopsis' the answer is that it is beneficial but not essential, however it may be more pertinent to ask 'what is the precise nature of the benefit?'
Congenital Ocular Motor Apraxia.
Morag McIndoe
Aim: To report the ocular and general features of a group of patients with Congenital Ocular Motor Apraxia (COMA).
Methods: Twenty-one cases of COMA who presented to the clinic, were seen following a review of the clinical database or were siblings of presenting cases are reported. All had full paediatric, orthoptic, and ophthalmic examination including video recording of head movements and determination of family incidence. Thirteen cases had radiological examination.
Results: All cases showed the typical clinical features of COMA. In addition there was a variety of orthoptic, ophthalmic, paediatric and radiological findings. Half of the group had myopia, which ranged from -0.50 to -19DS. There were seven familial cases of COMA, which were associated with consanguineous marriage.
Conclusion: Patients with COMA may have a wide spectrum of ophthalmic and general abnormalities. The presence of familial cases within the group supports the theory of a genetic basis for some cases of COMA.
Attentional Visual Field Analysis using Fastpac.
I Cunningham;PC Knox;FJ Rowe; AC Fisher
Aim: To investigate the effect of dividing attention using conventional automated perimetry in normal, healthy young and elderly subjects.
Methods: A Humphrey Visual Field Analyzer was modified by the addition of external lasers, which introduced a task additional to the standard threshold field test by presenting red targets at fixation. Young and elderly subjects inexperienced in perimetry were recruited. Two standard 30-2 Fastpac visual fields were examined. Three attentional visual fields were completed which varied in difficulty. The number of targets at fixation decreased from 72 (high) to 48 (medium) and then 24 (low) in each attentional visual field. The effects on visual sensitivity were compared by dividing the central 30¨¬ degrees in four regions dependant on eccentricity. Accuracy, durations and manual response times in the different conditions were also compared.
Results: In high distraction conditions elderly subjects showed reduced visual sensitivity whereas young subjects had similar sensitivity compared to sensitivity for standard visual fields. As the numbers of distractors was reduced visual sensitivity was shown to improve for both groups. The duration time to complete the attentional visual field increased for both groups compared to the standard fields but measures of accuracy were broadly similar in both standard and attentional visual field tests for both groups. The manual response times in the attentional conditions increased for both groups in attentional conditions.
Conclusion: The loss in sensitivity in high distraction attentional visual fields for elderly subjects, longer durations and increase in response time suggest that motivational or cognitive status may have an impact on the interpretation of visual field results.
A National Survey To Assess The Prevalence Of Written Guidance For Occlusion And Practice Variation In The Treatment Of Amblyopia.
Sue Elliott
Aim: To assess the prevalence of written clinical guidance for occlusion treatment and variation in occlusion practice within Orthoptic departments in the United Kingdom (UK).
Method: A questionnaire was sent to every Orthoptic department in the UK. Questions asked about the existence of written guidance in departments and how this guidance had been developed. Subsequent questions asked about the treatment of amblyopia. Clinical scenarios of amblyopia were provided and departments had to indicate the occlusion in hours that would be prescribed.
Results: 190 of 240 questionnaires were returned; a response rate of 72%. 186 questionnaires were suitable for analysis. 66/186 (35%) of responding departments had written guidance for occlusion, 70 (38%) had some general department consensus on occlusion and 47 (25%) had no departmental consensus on occlusion and 3 (2%) declined to answer. Statistical analysis indicated there were significant differences between departments 'with guidance' and those 'without guidance', in the amount of occlusion prescribed if treating more severe amblyopia (6/60 vision). There were no significant differences in occlusion prescribed for less severe amblyopia (6/12 vision).
Conclusion: In the responding departments the prevalence of written guidance for occlusion treatment was low and there were significant variations in the amount of occlusion that would be prescribed. It is essential to have good quality, robust evidence on which to base clinical decisions.
Factors that influence the visual outcome in cases of infantile unilateral cataract.
Clare Dewsbery
Aim: To review retrospectively the records of a cohort of patients who presented before
6 months of age with unilateral cataract and identify factors that influenced the visual outcome.
Method: The records of children with unilateral infantile cataract, who had been examined since 1993 following the establishment of a new occlusion protocol, were reviewed. For analysis the children were divided into 2 groups, group A with visual acuity of 0.6 logMAR or better and group B with visual acuity of <0.6 logMAR. Factors examined were referral history, type of cataract, age at surgery, contact lens wear, ophthalmic complications, occlusion therapy, attendance record and distance from home.
Results: Thirty-two children met the inclusion criteria; 8 transferred to other hospitals leaving 24 cases for analysis. There were 11 (46%) children in group A with visual acuity ranging from 0.6 to 0.04 logMAR and 13 (54%) children in group B with visual acuity ranging from NPL to 0.74 logMAR. The median age at surgery was 8.5 weeks, (13 weeks group A; 7 weeks group B). There was a greater incidence of ophthalmic complications in group B. Nystagmus was present in 9 (37.5%) children, 8 of who were in group B and this was a significant factor in visual outcome, (p = 0.013). Compliance with the occlusion protocol was also a significant factor in visual outcome (p = 0.016). Further analysis indicated an association between occlusion compliance, visual outcome and distance from home, (p = 0.035)
Conclusion: A high incidence of ophthalmic complications, a delay in establishing daily contact lens wear and a failure to achieve 'good' compliance with occlusion therapy were associated with a poor visual outcome.
Pilocytic Astrocytoma of the Brainstem - a case report.
Claire Macintosh
Aim: To describe a case of pilocytic astrocytoma arising in the medulla, which presented as a sudden onset esotropia.
Method: A case is documented with history, neurological signs, orthoptic findings, and management. Pilocytic astrocytoma is discussed in relation to the literature.
Results: A small esotropia in a healthy 2 year old, presenting to a vision screening clinic, was the sole initial sign of a brainstem pilocytic astrocytoma. There was subsequent diagnosis of a mild VIth nerve palsy and development of other neurological signs including gaze evoked nystagmus and ataxia.
Conclusion: Pilocytic astrocytoma is a neuroepithelial tumour of the central nervous system, of low grade, occurring mainly in children and young adults and most commonly in the cerebellum. Pilocytic astrocytoma of the brainstem is much less common and carries a worse prognosis owing to difficulty in complete surgical resection. This is a rare condition, but the Orthoptist must remain aware that they may be the first point of referral in such cases and recognise signs indicative of urgent investigation.
A possible case of Heavy Eye Phenomenon
Morag McIndoe
Aim: To describe a case of possible heavy eye phenomenon and discuss the differential diagnosis.
Methods: Details are reported of a boy who presented at age 16 who had previously attended the Orthoptic department as a young child. Documentation of the case is presented including findings in childhood, findings at later presentation and photographic illustrations.
Results: The orthoptic findings for this boy when discharged at age 9 differed from the findings at age 16. At age 9 the patient showed good corrected visual acuity in each eye, good binocular functions and normal stereo acuity. At age 16, the patient had a variable right hypotropia, refractive error of -8.5/-1.25x5, left +0.25/-0.50x177.5 and axial lengths of right 26.22mm and left 22.86mm.
Conclusions: This is most likely a case of heavy eye phenomenon. Previous records are useful in determining the onset of the condition.
Recurrent Thyroid Eye Disease - A Case Series
EJ Wallace; CJ MacEwen.
Aim: To report recurrent thyroid eye disease (TED), which is unusual because the condition is considered a monophasic disease and recurrence is rarely reported.
Methods: A retrospective case note review was carried out on all patients who had attended the thyroid eye disease clinic in our hospital. Six cases with recurrence of their disease were identified. One case is presented in detail and the clinical findings of five similar cases are documented.
Results: Of the 6 cases, 5 were female. The average age at time of diagnosis with thyroid eye disease was 47 years and at the time of recurrence was 56 years. All were managed conservatively at their first presentation but 4 patients required radiotherapy to control the recurrence. Three patients required squint surgery after their disease reactivated. The most common operation for strabismus was an inferior rectus recession.
Conclusions: TED is considered to be a monophasic autoimmune disease with an initial active phase of progressive deterioration followed by a static phase with gradual improvement over the years. The cases presented show that the natural history of the disease does not always follow this conventional pattern and this is an important consideration when planning future management.
A Case Of Constant Esotropia With Diplopia Associated With Weight Loss In Anorexia Nervosa
B Manzouri; & GGW Adams
Aim: To describe the case of an adult female who presented with a constant esotropia with diplopia following the onset of anorexia nervosa, in who the control of her strabismus and diplopia improved as body weight was regained.
Methods: The orthoptic findings are presented and the outcome of treatment with botulinum toxin injection is reported.
Results: Botulinum toxin injection reduced the angle of deviation from 50¥Ä base out (BO) for distance and 45¥Ä BO for near, to 30¥Ä BO for distance and 25¥Ä BO for near. Post injection the patient reported a marked improvement in symptoms and experienced diplopia only when tired. Over time and in conjunction with weight gain the deviation was controlled to a microtropia with an associated latent component with demonstrable anomalous binocular vision.
Conclusion: This case shows the possible effects of anorexia on the balance of the oculomotor system with the onset of a convergent squint at a time of severe weight loss. Botulinum toxin injection under local anaesthetic may be the wisest and least invasive therapeutic choice in these patients, thereby avoiding a surgical procedure under general anaesthesia, which may be unsuitable in cases of anorexia.