Vergence Dysfunction Research Articles

A differential role for the posterior cerebellum in the adaptive control of convergence eye movements

IntroductionThe vergence oculomotor system possesses two robust adaptive mechanisms; a fast “dynamic” and a slow “tonic” system that are both vital for single, clear and comfortable binocular vision. The neural substrates underlying these vergence adaptive mechanisms in humans is unclear. MethodsWe investigated the role of the posterior cerebellum in convergence adaptation using inhibitory continuous theta-burst repetitive transcranial magnetic stimulation (cTBS) within a double-blind, sham controlled design while eye movements were recorded at 250hz via infrared oculography. ResultsIn a preliminary experiment we validated our stimulation protocols by reproducing results from previous work on saccadic adaptation during the classic double-step adaptive shortening paradigm. Following this, across a series of three separate experiments we observed a clear dissociation in the effect of cTBS on convergence adaptation. Dynamic adaptation was substantially reduced while tonic adaptation was unaffected. Baseline dynamic fusional vergence response were also unaffected by stimulation. ConclusionsThese results indicate a differential role for the posterior cerebellum in the adaptive control of convergence eye movements and provide initial evidence that repetitive transcranial magnetic stimulation is a viable tool to investigate the neurophysiology of vergence control. The results are discussed in the context of the current models of implicit motor adaptation of vergence and their application to clinical populations and technology design in virtual and augmented head mounted display architectures. Significance statementThe cerebellum plays a critical role in the adaptive control of motor systems. Vergence eye movements shift our gaze in depth allowing us to see in 3D and exhibit two distinct adaptive mechanisms that are engaged under a range of conditions including reading, wearing head-mounted displays and using a new spectacle prescription. It is unclear what role the cerebellum plays in these adaptive mechanisms. To answer this, we temporarily disrupted the function of the posterior cerebellum using non-invasive brain stimulation and report impairment of only one adaptive mechanism, providing evidence for neural compartmentalization. The results have implications for vergence control models and applications to comfort and experience studies in head-mounted displays and the rehabilitation of clinical populations exhibiting vergence dysfunctions.

Postconcussion: Receded Near Point of Convergence is not Diagnostic of Convergence Insufficiency

To determine the frequency of occurrence of receded near point of convergence (NPC) in patients with chronic concussion-related symptoms and in those with receded NPC to enumerate the frequency of convergence insufficiency and other oculomotor disorders. Retrospective cross-sectional study. Clinic charts were retrospectively reviewed for the prior 3.5 years to identify all patients < 21 years old who were > 28days postconcussion, had chronic concussion-related symptoms, had normal visual acuity, and had received a comprehensive sensorimotor examination. The frequency of receded NPC and oculomotor diagnoses were determined. Of the 83 eligible patients, 74 (89%) had receded NPC. Of these, 70 (95%) had oculomotor disorders; 30 (41%) had disorders of accommodation only; 21 (28%) had convergence insufficiency and accommodation deficits; and 6 (8%) had convergence insufficiency only. Six (8%) had a convergence deficit other than convergence insufficiency (all with concurrent accommodative disorders); 4 (5%) had both a nonspecific vergence dysfunction and accommodation deficits; 2 (3%) had convergence excess only; and 1 (1%) had both convergence excess and accommodative deficits. A receded NPC was present in the majority of young patients with chronic postconcussion symptoms. Associated with numerous underlying oculomotor dysfunctions, the clinical finding of a receded NPC is not synonymous with the diagnosis of convergence insufficiency. Because treatment options for the various oculomotor dysfunctions differ, it is prudent that these patients undergo a thorough examination of their vergence and accommodative systems so that an accurate diagnosis can be made and appropriate treatment prescribed.

Review of school vision screening guidelines

Background: Vision screenings are important in identifying visual anomalies likely to disrupt the physical, intellectual, social and emotional development of children. School health services globally include vision screenings, complementing a variety of associated screening services.Aim: This review article provides evidence for content, provision and efficacy of the vision screening services for children of school-going age and reports on the current practice of children’s vision screenings worldwide including in South Africa.Methods: Studies were identified from PubMed, Ebscohost and Science Direct with the search terms utilised during the selection of electronic articles and journals for the review. The target population includes children of school-going age from 6 to 19 years without previously known conditions associated with visual anomalies and learning-related problems. The quality of vision screening programmes and policies for the school-going age children in different countries were evaluated using Wilson and Jungner criteria.1Results: Vision screening programmes worldwide appear to support comprehensive vision screening methods among pre-schoolers (from birth to ≤ 6 years vs. children of school-going age). The development of vision screening procedures in some countries in the United States of America (USA) was found to be grounded on epidemiologic findings and principles. These may have contributed towards the formulation of national vision screening guidelines for pre-schoolers that supported the detection of amblyopia and its associated conditions such as strabismus, anisometropia and myopia. School-going children’s vision screenings are not supported worldwide as research has shown that there is lack of benefits for detecting other visual anomalies such as vergence and accommodative dysfunctions. This is despite evidence provided by the literature reviewed that an association exists between prevalent accommodation and vergence dysfunctions including poor ocular motilities and poor near-vision, among children of school-going age with poor academic performance.Conclusion: The guidelines worldwide support school vision screenings, especially for the pre-schoolers by the school health nurses, with other programs having considered the teachers, optometrists or orthoptists as the appropriate personnel to conduct the school vision screenings. There is still a need for the effectiveness of the school vision-screening programmes to be investigated related to the importance of detecting convergence and accommodative dysfunctions for the school going age children.

Vergence Profile and Prevalance of Non-Strabismic Vergence Anomalies Among School Children in Abia State, Nigeria

ABSTRACTPurpose: To determine the prevalence of non-strabismic vergence anomalies and their relationship with age, gender, and school level in children aged 10–16 yearsMethod: A cross-sectional study was conducted among 537 children (255 male, 282 females; mean age 13.0 ± 2.0, years) selected from nine schools using stratified, cluster, and random sampling. The participants completed a Convergence Insufficiency Symptom Survey (CISS) and eye examinations, including the measurement of visual acuity, non-cycloplegic refraction, cover test, near point of convergence, fusional vergences, accommodative functions, and ocular health evaluation. All binocular tests were performed following the subjective refraction with the corrective lenses in place, if prescribed.Results: The prevalence of low suspect, high suspect, and definite convergence insufficiency was 9.6%, 5.8%, and 4.1%, respectively. Other prevalence estimates included convergence excess (2.9%), fusional vergence dysfunction (2.6%), basic exophoria (1.7%), basic esophoria (2.8%), divergence insufficiency (0.8%), and divergence excess (0.6%). The prevalence of high suspect (p < 0.01) and definite (p < 0.01) convergence insufficiency was significantly higher in older than younger children, and as expected, in secondary more so than primary school children (p = 0.01). There was no statically significant association between gender and various vergence anomalies.Conclusion: The study showed that vergence anomalies are common vision conditions among Abia State school children. Given the importance of visual skills in learning and academic achievements, there is a need to develop screening and management strategies that will target those visual conditions to prevent educational and social progress being affected.

Symptomatic accommodative and binocular dysfunctions from the use of flat-panel displays.

To determine the presence of symptomatic accommodative and non-strabismic binocular dysfunctions (ANSBD) in a non-presbyopic population of video display unit (VDU) users with flat-panel displays. One hundred and one VDU users, aged between 20 to 34y, initially participated in the study. This study excluded contact-lens wearers and subjects who had undergone refractive surgery or had any systemic or ocular disease. First, subjects were asked about the type and nature of eye symptoms they experienced during VDU use. Then, a thorough eye examination excluded those subjects with a significant uncorrected refractive error or other problem, such as ocular motility disorders, vertical deviation, strabismus and eye diseases. Finally, the remaining participants underwent an exhaustive assessment of their accommodative and binocular vision status. Eighty-nine VDU users (46 females and 43 males) were included in this study. They used flat-panel displays for an average of 5±1.9h a day. Twenty subjects presented ANSBD (22.5%). Convergence excess was the most frequent non-strabismic binocular dysfunction (9 subjects), followed by fusional vergence dysfunction (3 subjects) and convergence insufficiency (2 subjects). Within the accommodative dysfunctions, accommodative excess was the most common (4 subjects), followed by accommodative insufficiency (2 subjects). Moderate to severe eye symptoms were found in 13 subjects with ANSBD. Significant eye symptoms in VDU users with accommodative and/or non-strabismic binocular dysfunctions often occur and should not be underestimated; therefore, an appropriate evaluation of accommodative and binocular vision status is more important for this population.

Refractive and binocular vision status of optometry students, Ghana

To investigate the refractive and non-strabismic binocular vision status of Optometry students in University of Cape Coast, Ghana and to establish any associations between these conditions. A cross sectional study of 105 Optometry students were taken through a comprehensive optometric examination to investigate the refractive and non-strabismic binocular vision status. Fisher’s exact test (IBM SPSS version 21) was used to assess association between these conditions. Prevalence of refractive error and non-strabismic binocular vision dysfunctions were 59.0% and 34.3% respectively. Prevalence of specific refractive errors were 17.1% myopia, 19.0% hyperopia and 22.9% astigmatism. Non-strabismic accommodative and vergence dysfunctions were found to be 21.9% and 12.4% respectively. Specific types of accommodative and vergence disorders were as follows: accommodative fatigue (8.6%), accommodative infacility (6.7%), accommodative insufficiency (4.7%) and accommodative excess (1.9%), convergence insufficiency (1.9%), convergence excess (1.0%), divergence insufficiency (2.9%), basic exophoria (1.9%), and basic esophoria (4.7%). There was a significant association between refractive errors in general and accommodative fatigue (p = 0.030) and between myopia and accommodative excess (p= 0.028). It is critical that potential primary eye care practitioners become aware of their refractive and non-strabismic binocular vision status.Journal of Medical and Biomedical Sciences (2016) 5(2), 24-29

A review of the classification of nonstrabismic binocular vision anomalies

There are conflicting and confusing ideas in literature on the different types of accommodative and vergence anomalies as different authors turn to classify them differently. This paper sought to review literature on the different classifications and types of nonstrabismic binocular vision anomalies and harmonize these classifications. Search engines, namely Google scholar, Medline, Cinahl and Francis databases, were used to review literature on the classification of accommodative and vergence dysfunctions using keywords like &lt;em&gt;binocular vision dysfunctions&lt;/em&gt;, &lt;em&gt;classification of nonstrabismic binocular vision disorders or anomalies&lt;/em&gt;, &lt;em&gt;accommodative disorders/anomalies classification&lt;/em&gt; and &lt;em&gt;vergence disorders/anomalies classifications&lt;/em&gt;, and included works that described these anomalies. Nonstrabismic binocular vision anomalies are classified as accommodative and vergence anomalies. There are three different major types of accommodative anomalies, namely accommodative insufficiency, accommodative infacility (accommodative inertia), and accommodative excess (accommodative spasm), and seven different types of vergence anomalies (convergence insufficiency, convergence excess, divergence insufficiency, divergence excess, basic esophoria, basic exophoria and fusional vergence dysfunctions), which are functional in origin. Functionally, there is a commonly reported interaction between accommodative and convergence insufficiency referred to as pseudoconvergence insufficiency. Accommodative paralysis (subtype of accommodative insufficiency) and vergence anomalies – &lt;em&gt;i.e.&lt;/em&gt;, convergence paralysis, convergence spasm and divergence paralysis – are non-functional in origin with underlying systemic disease etiologies. Systemic convergence insufficiency, associated with subnormal accommodation, is a non-functional interaction between the accommodative and convergence insufficiency. The classification of nonstrabismic binocular vision anomalies is based on the description of the clinical signs and the underlying etiology either functional or non-functional in origin. Proper diagnosis and management involves investigation of the underlying etiology in addition to the battery of binocular vision test procedures.

Binocular vision and abnormal head posture in children when watching television.

To determine the association between the binocular vision and an abnormal head posture (AHP) when watching television (TV) in children 7-14y of age. Fifty normal children in the normal group and 52 children with an AHP when watching TV in the AHP group were tested for spherical equivalents, far and near fusional convergence (FC) and fusional divergence (FD) amplitudes, near point of convergence, far and near heterophoria, accommodative convergence/ accommodation ratio and stereoacuity. The values of these tests were compared between the two groups. The independent t test was applied at a confidence level of 95%. The far and near FC amplitudes and far FD amplitudes were lower in the AHP group (the far FC amplitudes: break point 13.6±5.4(Δ), recovery point 8.7±5.4(Δ). The near FC amplitudes: break point 14.5±7.3(Δ), recovery point 10.3±5.1(Δ). The far FD amplitudes: break point 3.9±2.7(Δ), recovery point 2.6±2.3(Δ)) compared with those in the normal group (the far FC amplitudes: break point 19.1±6.2(Δ), recovery point 12.4±4.5(Δ). The near FC amplitudes: break point 22.3±8.0(Δ), recovery point 16.1±5.7(Δ). The far FD amplitudes: break point 7.0±2.1(Δ), recovery point 4.6±1.9(Δ)). Other tests presented no statistically significant differences. An association between the reduced FC and FD amplitudes and the AHP in children when watching TV is proposed in the study. This kind of AHP is considered to be an anomalous manifestation which appears in a part of puerile patients of fusional vergence dysfunction.

Symptomatic vergence disorders in junior high school children in Ghana

Background: Optometrists in Ghana are hampered in performing comprehensive binocular vision assessments, because of the lack of appropriate instruments leading to a paucity of data on vergence disorders and their association with asthenopia among Ghanaian school children.Aim: To establish the prevalence of symptomatic vergence disorders among junior high school (JHS) children in Cape Coast Metropolis, Ghana, in their habitual (vision) states and investigate if there were any associations between these disorders and specific asthenopic symptoms.Methods: A prospective cross-sectional school-based study using a multistage sample of 627 participants aged 12–17 years from JHSs in Cape Coast Metropolis. Participants completed a reliable asthenopic symptoms questionnaire and 220 participants who expressed two or more severe or very severe symptoms were selected for comprehensive binocular vision assessment in their habitual vision state.Results: The prevalence of symptomatic vergence disorders among JHS children in Cape Coast Metropolis was 14.8%. For specific symptomatic vergence disorders, the prevalence was: 1.4% basic esophoria, 1.4% basic exophoria, 8.6% convergence insufficiency, 1.8% convergence excess, 0.8% fusional vergence dysfunctions and 0.8% divergence excess. No participant had symptomatic divergence insufficiency. The study revealed significant associations between some specific symptomatic vergence disorders and specific asthenopic symptoms even though all of these asthenopic symptoms overlapped in other vergence disorders.Conclusion: Presenting complaints of specific asthenopic symptoms does not differentiate between specific types of vergence disorders. A comprehensive binocular vision assessment is vital in the diagnosis and management of these disorders to relieve asthenopia.

Vergence findings and horizontal vergence dysfunction among first year university students in Benin City, Nigeria

PurposeThe study was designed to determine the prevalence of vergence dysfunctions among first year university students in Nigeria and to document the measures that define the vergence system of the visual system. MethodsA cross-sectional study of first year students of the University of Benin, Benin City, Nigeria, who presented for the mandatory eye examination as part of their medical examinations required for clearance was conducted. A battery of tests that defines the vergence system including near and far phoria, positive and negative fusional vergence amplitudes at far and near, near point of convergence (NPC) and AC/A ratio were measured using conventional clinical protocols. ResultsThe prevalence of vergence dysfunction among 212 first year university students who satisfied the inclusion criteria and gave consent to participate was 12.7%, with convergence insufficiency being the most common vergence dysfunction. Blurred vision, headache and diplopia were the most frequently reported visual symptoms. ConclusionThere is a considerable prevalence of previously undiagnosed vergence dysfunctions in this population of students. The study underscored the need to carry out a thorough binocular vision assessment as part of the battery of tests administered to newly admitted students in this community to forestall any adverse effect the presence of vergence dysfunctions might have on the academic activity of university students.

Vergence anomalies in a sample of high school students in South Africa

AimTo study the prevalence of nearpoint vergence anomalies (convergence insufficiency, convergence excess and fusional vergence dysfunction) and association with gender, age groups, grade level and study site (suburban and rural). MethodsThe study design was cross sectional and data was analyzed for 1201 high school students aged 13–19 years who were randomly selected from 13 high schools in uMhlathuze municipality. Of the total sample, 476 (39.5%) were males and 725 (60.5%) were females. The visual functions evaluated included refractive errors, heterophoria, near point of convergence, accommodative functions and fusional vergences. Possible associations between vergence anomalies and demographic variables (gender, age groups, school grade levels and study site) were explored. ResultsPrevalence estimates were 11.8%, 6% and 4.3% for low suspect, high suspect and definite convergence insufficiency, and 1.9% for the pseudo convergence insufficiency. Convergence excess prevalence was 5.6%, and fusional vergence dysfunction was 3.3%. The prevalence of low suspect CI was significantly higher in suburban than in rural participants (p=0.01), the reverse was the case for pseudoconvergence insufficiency while the prevalence of convergence excess was significantly higher in the younger than in the older age group (p=0.02). No other category showed any statistically significant associations with vergence anomalies. ConclusionThe prevalence estimates for vergence anomalies in a sample of black high school students in South Africa were relatively low. Only study location and age influenced some vergence anomalies. Identification and referrals are important steps toward diagnosis and treatment for vergence anomalies. Further studies to compare vergence anomalies in various racial populations will be relevant.

The Effects of Vertical Yoked Prism on Horizontal Heterophoria.

Vertical yoked prisms (VYPs) have been recommended for the remediation of vergence dysfunction, but the evidence base for their use is mostly low level. This study investigates the effect of VYP on horizontal subjective dissociated heterophoria. Phoria measurement was performed in primary gaze with the Modified Thorington technique at 3 m and at 40 cm on 40 nonpresbyopic young adults. Subjects were seated and head position was held constant. Baseline measures (without yoked prism) of distance and near phoria were measured. Phorias were measured again through the following range of VYP, randomly presented: 2 prism diopters (Δ) base up (BU), 2Δ base down (BD), 5Δ BU, and 5Δ BD. Twenty-six subjects also had their phorias measured with control lenses of +0.125 DS OU (because of unavailability of Plano trial lenses) randomly presented along the other conditions. There was no significant difference overall between phoria measured in any of the yoked prism conditions, including the baseline measure, at distance or near. Neither was there evidence of a predictable esophoric or exophoric shift with either BU or BD prism. Vertical yoked prisms did not exert any immediate effect on horizontal phoria in young adults when posture was controlled. This suggests that, if VYPs do indeed improve horizontal vergence problems, they do not do so by a direct or immediate impact on horizontal phoria.

Prevalence of general binocular dysfunctions among rural schoolchildren in South Korea

Background/PurposeTo assess the prevalence of nonstrabismic accommodative and vergence dysfunctions among primary schoolchildren in Hampyeong, a rural area of South Korea. MethodsFive hundred and eighty-nine primary schoolchildren, 8–13 years old, were each given a thorough eye examination, including binocular-vision testing, near point of convergence, horizontal phoria measurement by von Graefe, and negative and positive vergence amplitudes with prism bar, to determine any form of accommodative or vergence dysfunctions. ResultsOf the 589 participants examined, 168 (28.5%) primary schoolchildren presented some form of nonstrabismic accommodative or vergence dysfunctions. The prevalence of accommodative dysfunctions and vergence dysfunctions was 13.2% and 9%, respectively. Convergence insufficiency (10.3%) was more prevalent than convergence excess (1.9%), and accommodative insufficiency (5.3%) was more prevalent than accommodative excess (1.2%). ConclusionThis study suggests that nonstrabismic accommodative and vergence dysfunctions are prevalent in the rural area of South Korean primary schoolchildren, and convergence insufficiency was the most prevalent.

Vision Therapy 프로그램의 양안시기능 개선 효과에 대한 메타분석

목적: Vision therapy 프로그램이 양안시기능 개선에 주는 효과를 통계적으로 종합하기 위하여 전체평균 효과크기, 종속변수별 평균 효과크기 그리고 대상특성과 처치특성에 따른 효과크기를 메타분석 기법을 이용하여 분석하고자 하였다. 방법: 자료의 분석을 위해 vision therapy 프로그램을 적용하고 그 효과를 분석한 국내 선행연구 14편을 선정하여 메타분석하였다. 결과: 전체평균 효과크기는 1.207로 높은 수준의 효과크기를 나타내었다. 양안시이상 유형별 하위영역의 평균 효과크기는 버전스 이상 그룹(2.989)이 가장 높았으며, 조절기능이상 그룹(0.868), 조절기능과 버전스 모두 이상이 있는 그룹(0.692) 순이었다. 대상특성에 따른 효과크기는 중복장애가 없는 양안시이상 그룹(2.509)을 대상으로 실시한 vision therapy가 가장 컸으며, 주당횟수별 평균 효과크기는 주당 7회의 처치 때 2.310으로 가장 큰 효과크기를 나타내었다. 그리고 처치기간에 따른 효과크기는 8주에서 2.019로 양안시기능 개선을 위한 vision therapy가 가장 효과적이었다. 결론: Vision therapy 효과에 대한 각각의 연구결과를 평균 효과크기로 변환하고 이를 객관화하는 방법을 통해 양안시기능 개선을 위한 치료가 효과적임을 증명할 수 있었다. Purpose: In order to aggregate effect of the improvement of binocular vision function by vision therapy, total mean effect size, mean effect size by dependent variables, and effect size by characteristics of the subjects and characteristics of treatment were analyzed by meta-analysis. Methods: We analyzed data from 14 Korean National primary studies, which reported effects of vision therapy programs, using meta-analysis. Results: The effect size of total mean was 1.207, which showed high effect. The mean effect size according to the subcategory of the binocular dysfunctions was the highest for vergence dysfunctions group (2.989), followed by accommodative dysfunctions group (0.868) and group with both vergence dysfunctions and accommodative dysfunctions (0.692). The effect size according to the characteristics of the subjects was the highest in the vision therapy conducted in the binocular dysfunctions group (2.509) that had no other dysfunctions. The mean effect size according to the number of programs was the highest (2.310) for 7 times a week. Vision therapy for improving the binocular functions was the most effective (2.019) in 8 weeks later from vision therapy start. Conclusions: It can prove that the therapy for the improvement of binocular vision function is effective through that each result of the vision therapy effect is converted to mean effect size, and being objectifying the mean effect size.

초등학생들의 양안시이상과 학업성취도와의 상관성 연구

목적: 초등학생들의 비사시성 양안시이상과 학업성취도와의 상관성을 알아보고자 하였다. 방법: 1,123명의 부모와 학생(8~13세)을 대상으로 COVD-QOL 측정 도구를 사용하여 점수가 20점 이상인 어린이 188명을 선별하였다. 이들 중에서 다시 사시, 약시, 안질환 및 전신질환이 없고 콘택트렌즈를 착용하지 않은 검사기준에 적합한 어린이 123명을 대상으로 양안시기능 검사를 시행하였다. 학업성취도는 2010년 2학기와 2011년 1학기에 시행한 국어, 수학, 사회, 과학, 영어 점수를 사용하였다. 결과: 눈 증상이 있는 초등학생 123명 중 93명에서 비사시성 양안시이상으로 판단되었고, 비사시성 양안시이상 중 조절이상은 과학과 영어, 버전스이상은 국어, 수학, 사회, 과학 그리고 영어에서 유의한 상관관계를 보였다. 결론: 조절이상과 버전스이상 모두 학업성취도와 유의한 상관성을 보여 학업성취도를 저하시키는 요인인 것으로 판단되었다. Purpose: The purpose of this study was to investigate the correlation between non-strabismic binocular dysfunctions and academic achievement for primary school children. Methods: A total of 1,123 parents and their children aged 8-13 years responded to the College of Optometrists in Vision Development Quality of Life (COVD-QOL) questionnaire. Among the all participants, 123 children who have <TEX>${\geq}20$</TEX> of visual symptom scores, no amblyopia, no strabismus, no any ocular and systemic pathology, and no contact lenses wearing were chosen for this study finally. Binocular functions were evaluated for final subjects. Results: Of 123 primary school children who have criteria-eligible symptoms 93 had non-strabismic binocular dysfunctions. Accommodative dysfunction was significantly correlated to subjects of science and English, and vergence dysfunction was also significantly correlated to Korean, mathematics, social science, science and English in the final subjects. Conclusions: Correlations between academic achievement and accommodative/vergence dysfunctions were statistically significant. Therefore, accommodative/vergence dysfunctions may be factors to affect academic achievement.

Accommodation and vergence status among the 3rd and 4th graders in a mainstream school in Gauteng*

Aim: The data presented in this paper is obtained from the study on the prevalence of visual deficien-cies in mainstream and learning disabled schools which revealed no difference in the prevalence of visual deficiencies in both schools. One of the objectives of this study was to determine the visual status of each learner in each of the two groups (mainstream and learning disabled). The findings of the study revealed that both groups presented with different visual deficiencies including accommodation, vergence deficiencies and poor ocular motilities which can contribute towards influencing the children’s learning skills negatively. The visual profile on the accommodative and vergence systems of the children from the mainstream school is further analysed in this paper to determine the prevalence of deficiencies in the 8-13 year-olds, and to support inclusion of the evaluation of these visual skills in the school vision screening protocol.Method: One hundred and twelve (112) children had an expanded vision screening, with eighty (80) from the mainstream school in Johannesburg aged 8-13 years. The expanded vision screeningincluded the measurement of visual acuity (Snellen Acuity), refractive error (static retinoscopy), accommodation (accuracy, facility and amplitude), evaluation of the vergence system (accuracy, facility and amplitude) and ocular motilities (direct ob-servation). Of the 80 children from the mainstream school, only 73 children’s results were consideredlearning performance of children, especially those of school-going-age. The study therefore supports the expanded vision screening of all school-going-children in South Africa to include visual efficiency skills (accommodation and vergence systems) for appropriate and early identification of the barriers and seven subjects were excluded due to their poor responses to the tests.Kolmogorov-Smirnov test was utilized to assess the normality of distribution of accommodative and vergence status of children from the mainstream school in Gauteng. Depending on the outcome of the normality, the T-test was used to analyse the data. The distribution of accommodative and vergence status (amplitudes and facilities) were found to be different from the normal distribution due to p-values found to be less than 0.05.Results: The results indicated that 12.3% had poor accommodation facility, 10% had poor accommodation amplitude, 17% had poor convergence amplitude and 21.9% had poor vergence facility. The prevalence of poor vergence facility was found to be 21.9%, higher than all the visual efficiency skills evaluated. However, the co-existence of both accommodative and vergence dysfunctions was not found, since subjects presented with either accommodative (isolated) or vergence (isolated) dysfunctions.Conclusion: The results considered were for tests performed subjectively, and therefore that could have led to the identified statistical outliers (due to inconsistent responses) in the analysis of data for the prevalence of poor accommodative (12.3%) and vergence (21.9%) facility. The prevalence of accommodative and vergence dysfunctions although low in some instances is a concern. There is definitely a need for early identification of visual deficiencies that can impact negatively on the to learning. (S Afr Optom 2012 71(1) 22-31)

Neuro-ophthalmology of movement disorders

Movement disorders commonly present with ocular features. The purpose of this review is to outline neuro-ophthalmologic findings that can help in diagnosis, treatment and determining prognosis in patients with movement disorders. Common movement disorders with ophthalmic symptoms include extrapyramidal disorders such as Parkinson disease-associated dry eye, decreased blink rate, and vergence dysfunction, and progressive supranuclear palsy-related lid retraction, frequent square-wave jerks and supranuclear gaze palsy. Multisystem atrophy can present with gaze-evoked horizontal or positional downbeat nystagmus and impaired vestibulo-ocular reflex suppression. Genetic disorders such as Huntington disease produce increased saccadic latencies and impaired suppression of saccades to presented stimulus, whereas Wilson disease is associated with saccadic pursuits, increased antisaccade latencies and decreased pursuit gain. Whipple's disease can present with supranuclear gaze palsy and characteristic oculomasticatory myorrhythmia. Movement disorders commonly present with ocular features. Knowledge of these ocular symptoms can assist the ophthalmologist in diagnosis and treatment of movement disorders.

Vergence in mild traumatic brain injury: A pilot study

Vergence dysfunction in individuals with mild traumatic brain injury (mTBI) may have a negative effect on quality of life, functional abilities, and rehabilitative progress. In this study, we used a range of dynamic and static objective and subjective measures of vergence to assess 21 adult patients with mTBI and nearwork symptoms. The results were compared with 10 control adult subjects. With respect to dynamic parameters, responses in those with mTBI were slowed, variable, and delayed. With respect to static parameters, reduced near point of convergence and restricted near vergence ranges were found in those with mTBI. The present results provide evidence for the substantial adverse effect of mTBI on vergence function.

Vergence dysfunction in mild traumatic brain injury (mTBI): a review

Vergence eye movements are used to track objects that move in depth in one's binocular visual field to attain and maintain a fused and single percept. The mechanism and control of vergence eye movements involves complex neurological processes that may be compromised in individuals with traumatic brain injury, thus frequently resulting in a wide range of vergence dysfunctions and related near-work symptoms, such as oculomotor-based reading problems. This paper presents a review of the vergence system and its anomalies in mild traumatic brain injury, as well as their diagnostic and therapeutic clinical ramifications. Implications related to brain imaging and human neuroplasticity are also considered.

Central Crosstalk for Somatic Tinnitus: Abnormal Vergence Eye Movements

BackgroundFrequent oulomotricity problems with orthoptic testing were reported in patients with tinnitus. This study examines with objective recordings vergence eye movements in patients with somatic tinnitus patients with ability to modify their subjective tinnitus percept by various movements, such as jaw, neck, eye movements or skin pressure.MethodsVergence eye movements were recorded with the Eyelink II video system in 15 (23–63 years) control adults and 19 (36–62 years) subjects with somatic tinnitus.Findings1) Accuracy of divergence but not of convergence was lower in subjects with somatic tinnitus than in control subjects. 2) Vergence duration was longer and peak velocity was lower in subjects with somatic tinnitus than in control subjects. 3) The number of embedded saccades and the amplitude of saccades coinciding with the peak velocity of vergence were higher for tinnitus subjects. Yet, saccades did not increase peak velocity of vergence for tinnitus subjects, but they did so for controls. 4) In contrast, there was no significant difference of vergence latency between these two groups.InterpretationThe results suggest dysfunction of vergence areas involving cortical-brainstem-cerebellar circuits. We hypothesize that central auditory dysfunction related to tinnitus percept could trigger mild cerebellar-brainstem dysfunction or that tinnitus and vergence dysfunction could both be manifestations of mild cortical-brainstem-cerebellar syndrome reflecting abnormal cross-modality interactions between vergence eye movements and auditory signals.