Academic literature on the topic 'Convergence oculaire'

Introducci.n. El cuestionario Convergence Insufficiency Symptoms Survey, (CISSV15)es una herramienta para el diagn.stico y seguimiento del tratamiento depacientes con insuficiencia de convergencia.Objetivo. Determinar la validez del cuestionario CISS-V15 para el diagn.stico de lainsuficiencia de convergencia, frente a las pruebas cl.nicas con que se eval.a elestado motor ocular de los pacientes atendidos en consulta optom.trica, en lasciudades de Recife y Salvador, Brasil.M.todos. Se llev. a cabo un estudio con enfoque cuantitativo, de tipo transversal ydescriptivo, con 50 pacientes de dos instituciones educativas en Brasil. Seseleccionaron aquellos que cumpl.an con los criterios de inclusi.n para aplicar elcuestionario, y se identificaron los pacientes con insuficiencia de convergencia yaquellos con visi.n binocular normal. Se analizaron los resultados del cuestionarioy las pruebas de motilidad ocular, para estimar medidas de tendencia central, yanalizar los valores de sensibilidad y especificidad del cuestionario.Resultados. La prueba alcanz. una sensibilidad de 0,83 y una especificidad de0,81.Conclusiones. Frente a las pruebas cl.nicas, el cuestionario CISS-V15 demostr.tener validez diagn.stica para las personas con insuficiencia de convergencia yaquellas con visi.n binocular normal, lo que lo convierte en una herramienta valiosapara el diagn.stico y seguimiento del tratamiento de los pacientes con insuficienciade convergencia.Palabras clave: trastornos de la motilidad ocular, visi.n binocular, astenopia,diplop.a, validez de las pruebas

1. Ocular convergence is usually accompanied by excyclotorsion of the eyes. Furthermore, the magnitude of cyclotorsion is dependent on the elevation of the eyes. The reason for this excyclotorsion during convergence is not understood. 2. Excyclotorsion could be produced by either increased activity in the inferior oblique muscle or decreased activity in the superior oblique muscle. An earlier study indicated that convergence may also be accompanied by a temporal (lateral) translation of the eye. This observation is more consistent with a relaxation of the superior oblique than contraction of the inferior oblique. 3. This hypothesis was tested by recording the activity of 31 neurons in the trochlear nucleus, which contains the superior oblique motoneurons. This was done in alert monkeys that were trained to make both versional and vergence eye movements. In addition, the cyclotorsion associated with convergence was measured in one of these monkeys. 4. A consistent excyclotorsion associated with convergence was observed. Trochlear unit activity decreased during convergence in all cells tested. The magnitude of this decrease was significantly greater than that seen with conjugate adduction. Furthermore, the size of the decrease varied systematically with ocular elevation in a manner that was consistent with earlier measures of cyclotorsion during convergence. 5. These results suggest that the excyclotorsion seen during convergence, and perhaps the lateral translation of the eye, are due to a relaxation of the superior oblique muscle. This relaxation during convergence is greater than that which accompanies similar conjugate movements of the eyes. We hypothesize that this peculiar pattern of muscle innervation has a motor rather than sensory function.(ABSTRACT TRUNCATED AT 250 WORDS)

Tout le trajet de la pensée de Merleau-Ponty est traversé – en certains cas de manière plus évidente que d’autres – par ce que je propose de définir comme une idée de la littérature et de la philosophie en tant que dispositifs de vision, pour utiliser une expression qui est née – et ce n’est pas un hasard – dans le domaine des études cinématographiques. Plus précisément, je voudrais montrer que Merleau-Ponty voit la littérature et la philosophie de son époque opérer comme des dispositifs de vision convergents, vision qui est à considérer, à son tour, comme une pratique corporelle et pas seulement oculaire. Cela dit, il faut souligner que de tels dispositifs visuels convergents ont la particularité de fonctionner avec les mots, et que Merleau-Ponty met l’accent sur leur différente efficacité à exprimer son époque. De plus, je pense que l’idée implicite de la philosophie en tant que dispositif de vision opérant par des mots « comme toute la littérature » a une place importante, mais pour l’instant pas assez développée, dans la dernière période de la pensée de Merleau-Ponty. En outre, je voudrais souligner qu’une telle perspective est cruciale aussi pour notre époque, bien que je crois qu’elle soit différente de celle de Merleau-Ponty. En effet, je pense que notre époque et celle de Merleau-Ponty sont toutes deux caractérisées par une tension entre l’importance croissante des images et la centralité traditionnelle du concept dans notre culture.The whole path of Merleau-Ponty’s thought is crossed – some times more evidently than others – by what I propose to qualify as the idea of literature and philosophy as visual apparatuses (dispositifs), to use an expression that was born – and not by chance – in the field of Film Studies. More precisely, I aim at asserting that Merleau-Ponty sees literature and philosophy working in his epoch as convergent apparatuses of vision, in turn understood as a bodily and not merely ocular practice. Immediately after that, I should specify that such convergent visual apparatuses peculiarly function by words, and that Merleau-Ponty stresses their different efficiency in expressing his epoch.Moreover, I think that the implicit idea of philosophy as a visual apparatus working by words “like all literature” has a particularly relevant but so far not consequently developed place in in the last period of Merleau-Ponty’s thought. Also, I would like to stress that such a perspective is crucial in our own time too, even though I consider it to be different from Merleau-Ponty’s. Indeed, I think that both our time and Merleau-Ponty’s are characterized by a tension between the increasing importance of images and the traditional centrality of the concept in our culture.L’intero percorso del pensiero di Merleau-Ponty è attraversato, in certi casi in modo più evidente, da quella che propongo di definire come un’idea di letteratura e di filosofia come dispositivi di visione, per usare un’espressione nata, non a caso, nell’ambito dei Film Studies. Più precisamente, vorrei mostrare come Merleau-Ponty concepisca la letteratura e la filosofia della sua epoca come dispositivi di visione convergenti, intesi come una pratica corporea e non già meramente ottica. Specificherò, poi, che tali dispositivi di visione convergenti operano attraverso la parola e che Merleau-Ponty sottolinea la loro diversa efficacia nell’esprimere la sua epoca. Ritengo inoltre che l’idea implicita di filosofia come dispositivo di visione che agisce tramite la parola, “come tutta la letteratura”, occupi un posto particolarmente decisivo, anche se non del tutto esplicitato, nell’ultimo periodo del pensiero di Merleau-Ponty. Vorrei poi mostrare come tale prospettiva si riveli cruciale anche nel nostro tempo, per quanto diverso rispetto a quello di Merleau-Ponty. Infatti, penso che tanto la nostra epoca quanto quella di Merleau-Ponty siano caratterizzate da una tensione tra l’importanza sempre crescente delle immagini e la tradizionale centralità riservata al concetto nella nostra cultura.

Recent studies have confirmed the relationship between head posture, mandibular position and visual focusing. A case-controlled study was conducted to assess the occurrence of ocular convergence defects between subjects with functional mandibular latero-deviation and healthy subjects in pediatric age. Sixty subjects (the study group) presented mandibular latero-deviation classified as functional according to the use of a clinical examination and frontal and basal tele-radiography. Sixty subjects without functional mandibular laterodeviation (control group) were selected randomly from all subjects seeking pediatric dental care and matched by gender and age to study group. All one hundred and twenty subjects were submitted to orthoptic tests performed by the same operator. These results seemed to confirm that in mandibular latero-deviation subjects ocular convergence defects occurred in greater frequency than in controls underlining the importance of role of pediatric dentistry among interdisciplinary cooperation.

Background: Vestibular and ocular motor deficits have been recognized as a key marker of the pathophysiology consistent with the diagnosis of concussion (Grady, 2010). Previous studies have been performed detailing the validity and clinical benefit of vestibular and ocular motor assessments (Corwin et al., 2015; Mucha et al., 2014). Recent guidelines and position statements have started recommending the use of vestibular and ocular motor assessment for pediatric patients (Matuszak et al., 2016), the most recent consensus statement recommending vestibular and ocular motor assessment by all practitioners within acute concussion settings (McCrory et al., 2017). Unfortunately, very little data exists with respect to vestibular and ocular motor performance in concussion patients between 8-12 years of age. The current study included a standardized administration of the Vestibular Ocular Motor Screening (VOMS) and the King-Devick Test (KD) in a sample of patients diagnosed with concussion and evaluated in an outpatient concussion clinic within 7 days of their initial date of injury. This study intended to evaluate performance on the VOMS and KD in an injured sample of patients 8-12 years of age. Methods: Pediatric patients diagnosed with concussion (n = 45) presenting to an outpatient concussion clinic within 7 days from their initial date of injury were administered a standardized version of the VOMS and KD. Patients were administered the VOMS and KD by certified athletic trainers educated and trained on administration. The VOMS consists of nine measures and was validated by the University of Pittsburgh (Mucha et al., 2014) as a symptom provocation measure with a symptom rating of 0-10 with convergence measured in centimeters, and scores of 6 cm or greater being indicative of abnormal. The KD is an ocular motor performance measure and has previously demonstrated reliability, sensitivity and specificity with respect to concussion diagnosis (Hecimovich et al., 2018). Demographic, acute injury, and baseline values were summarized using descriptive statistics. Point estimates and 95% confidence intervals were calculated for all end points. Pearson correlations were calculated based numerical values from the VOMS and KD data. Results: The total sample consisted of 14 females and 31 males, with a mean age of 10.6 + 1.4 years. 20% of the subjects (n = 9) reported a prior history of concussion with a total of 17 previous concussions reported. 13.3% of the sample (n = 6) reported a history of migraine and 4.4% (n = 2) reported a history of psychiatric diagnosis. Acute self-reported injury data based on signs and symptom markers were calculated including; dizziness (66.6%, n = 30), headache (82.2%, n = 37), vision problems (42.2%, n = 19), amnesia (35.5%, n = 16), and loss of consciousness (22.2%, n = 10). Descriptive statistics for baseline VOMS symptoms were recorded; headache (mean = 3.2 + 2.7, CI = 2.8-3.6), dizziness (mean = 1.3 + 1.7, CI = 1.1 -1.5) nausea (mean = 0.7 + 1.6, CI = 0.5-0.9), and fogginess (mean = 1.1 + 2.0, CI = 0.8 -1.4). VOMS convergence in centimeters across trials; T1 (mean = 5.1 + 5.2, CI = 4.6-5.9), T2 (mean = 6.2 + 5.8, CI = 5.3-7.1), and T3 (mean = 7.1 + 6.9, CI = 6.1-8.1). KD time in seconds; card 1 (mean = 22.4 + 9.5, CI = 21-23.8), card 2 (mean = 23.1 + 9.5, CI = 21.7-24.5), card 3 (mean = 27.2 + 9.3, CI = 25.8-28.6), and total (mean = 72.8 + 27.3, CI = 68.7-76.9). Pearson correlations revealed strong correlations across VOMS symptoms; headache (r = 0.89-0.99), dizziness (r = 0.78-0.98), nausea (r = 0.88-0.98), and fogginess (r = 0.89-0.98). Moderate correlations between KD time and convergence distance were observed; KD card 1 (convergence T1, r = 0.61, convergence T2, r = 0.58, convergence T3, r = 0.49), KD card 2 (convergence T1, r = 0.62, convergence T2, r = 0.58, convergence T3, r = 0.48), and KD total time (convergence T1, r = 0.59, convergence T2, r = 0.54, convergence T3, r = 0.46). Conclusion: To the best knowledge of the authors involved, this study is the first of its kind to explore the performance on the VOMS and KD in a sample of acutely injured (< 7 days) 8-12-year-old patients diagnosed with concussion. Several notable findings were observed. Headache was the most predominant symptom reported during VOMS administration and remained significantly higher than the other symptoms of dizziness, nausea, and fogginess. This finding may be the byproduct of increased difficulty in symptom description between the ages of 8-12. Further, correlations within symptoms were strong suggesting throughout VOMS administration symptoms remain relatively stable. Lastly, moderate relationships were noted between convergence on the VOMS and KD time scores. This is likely a result of both measures addressing ocular motor functioning but differing based on data medium (centimeters versus seconds). The current study was limited based on sample size and further data is necessary to draw larger conclusions based on 8-12-year-old injured VOMS and KD performance.

1. Single-unit recording studies in alert Rhesus monkeys characterized the vergence signal carried by abducens internuclear neurons. These cells were identified by antidromic activation and the collision of spontaneous with antidromic action potentials. The behavior of abducens internuclear neurons during vergence was compared with that of horizontal burst-tonic fibers in the medial longitudinal fasciculus (MLF) and to that of a large sample of unidentified abducens cells (presumably both motoneurons and internuclear neurons). 2. The results indicate that abducens internuclear neurons and lateral rectus motoneurons behave similarly during vergence eye movements: the majority of both groups of cells decrease their firing rate for convergence eye movements: a minority show no change for vergence. This finding is strongly supported by recordings of horizontal burst-tonic fibers in the MLF, the majority of which decrease their activity significantly for convergence eye movements. 3. These findings indicate that a net inappropriate vergence signal is sent to medial rectus motoneurons via the abducens internuclear pathway. Because medial rectus motoneurons increase their activity appropriately during symmetrical convergence, this inappropriate MLF signal must be overcome by a more potent direct vergence input. 4. Overall, both abducens internuclear neurons and lateral rectus motoneurons decrease their activity for convergence less than would be expected based on their conjugate gain. This implies that some degree of co-contraction of the lateral and medial rectus muscles occurs during convergence eye movements. 5. Some horizontal burst-tonic MLF fibers decrease their activity more for convergence than any recorded abducens neuron. These fibers may arise from cells in the nucleus prepositus hypoglossi or vestibular nuclei.

Ce travail a porté sur l'étude de certains facteurs physiologiques de la vison stéréo humaine particulièrement liés à la perception de relief dans un système de TV stéréo dynamique, et sur la compréhension des processus visuels stéréoscopiques humains à l'aide des modèles spectraux locaux. Nous avons étudié les différents types d'acuités stéréoscopiques sur tous les méridiens rétiniens aussi bien en position d’œil centrale qu'en position d’œil excentrique chez es sujets physiologique et pathologiques. L'accommodation et la convergence, deux facteurs principaux de la vision en relief en système stéréo,ont également été étudiées en détail, permettant d'en déduire la manière selon laquelle le système visuel humain résout le conflit entre l'accommodation et la convergence. Le problème de la qualité de sensation du relief en présence des distorsions géomagnétiques été abordé. Dans ce cadre, deux types de distorsions géométriques ont été distingué, et sur leur effet sur le confort visuel et sur la sensibilité à la disparité binoculaire a chiffré dans diverses situations. Enfin, en vue d'appréhender la processus de traitement et de codage de l 'information stéréo , nous avons étudié l'influence du contenu spectral local des images monoculaires sur la vision stéréo humaine en introduisant un modèle bidimensionnel espace/fréquence spatiale. Fondé sur la transformation de Wigner-Ville. Et la transformation de cosinus discrète bidimensionnelle
This thesis is concerned with the stud of certain hurnan stereo vision cues. Particularly relevant ta depth perception in a dynamic 3d (three-dimensional) stereoscopic TV and with t he understanding of human stereoscopic visual processes using local spectral models. We have studied different types of stereo acuity all the retinal meridian in both central and eccentric eye positions, in physiological and pathological subjects. Accomdation and convergence, the two essentiel depth perception cues in 3D Tvs, have benn investigated in detail, allowing ta get insight into the way the human visual system behaves in arder to resolve the conflict between accommodation and convergence. The quality problem of depth perception in the presence of geometrical distortions was also addressed. Within this framework. Two types of geornetrical distortions have been distinguished, and their affect the visual comfort and binocular disparity sensitivity bas been detailed in various situations. Finally, in arder ta get an insight into the stereo informatian processing and coding processes, we have studied the influence of the monocular images' local spectral content on human stereo vision by employing a 2D (two-dimensional) space/spatial-frequency model based on using the 2D Wigner-Vill distribution, and the 2D discrets cosine transformation

Kinesiology
Ph.D.
Dysfunctions of ocular motor and binocular vision are some of the most commonly observed problems in patients with severe traumatic brain injury. Secondarily, subjective complaints of compromised vision and ocular motor functions are also sometimes reported in mild traumatic brain injuries (mTBI). Simple ocular/vision assessments such as near point of convergence (NPC), the King-Devick Test (KDT), and stereoacuity can be performed to identify and assess these deficits, but their diagnostic accuracy has yet to be thoroughly investigated. The purpose of this study was to determine if differences exist in NPC, KDT, and stereoacuity test scores between concussed and control athletes, and to determine the diagnostic accuracy of these tests. A multicenter control group design was utilized. The independent variable was group (control vs. concussed). The dependent variables were the ocular test scores from the NPC, KDT, and stereoacuity tests. Participants were recruited from several collegiate athletic programs. In total 34 healthy, non-concussed controls (21 male, 13 female) aged 19 + 1.5 years and 19 concussions (11 male, 8 female) aged 20.42 + 1.5 years participated in the study. A concussion was operationally defined as a complex pathophysiological process affecting the brain, induced by biomechanical forces, that was diagnosed by a health care professional through the use of signs and symptoms scales, balance and neurocognitive testing. Data were analyzed using descriptive and inferential statistics. T-tests and chi-squares were performed to ensure there were no significant differences between groups on specific demographic or relevant prognostic variables (sport, sex, and concussion history). T-tests were employed to identify significant differences between groups on ocular test scores. Then clinical and statistical cutoffs for all three tests were determined. Based off of these cutoffs sensitivity, specificity, and likelihood ratios were determined for each assessment. Furthermore, receiver operating characteristic (ROC) curves were calculated to help determine the diagnostic accuracy of these assessments. The alpha level was set at p < .05 and the SPSS for Windows, Version 21.0, statistical program (IBM, Inc., Armonk, NY) was used for all data analysis. Significant differences were found between groups for all three ocular assessments. NPC demonstrated a statistical cutoff of 5.5 cm, which provided a sensitivity of 79% and specificity of 76% and an AUC of 0.827. For the KDT, a statistical cutoff time of 49.5s demonstrated a sensitivity of 58% and specificity of 72% with an AUC of 0.658. Lastly, for stereoacuity a statistical cutoff point of 28.50 arc sec was found which produced a sensitivity of 65% and specificity of 54% with a maximum AUC of 0.706. All three tests demonstrated their potential to positively contribute to the diagnosis of a concussion.
Temple University--Theses

The relationship between accommodation and myopia has been under investigation for many years, and the effort to understand it is ongoing. In this thesis, an introduction to the state of myopia research is given first, with particular reference to studies of accommodation and higher-order ocular aberrations, which feature in the subsequent chapters. Following a brief introduction to the general technique of aberrometry and visual stimulus control using adaptive optics, the development of a monocular adaptive optics instrument for this purpose is described. The instrument is used to vary a dioptric stimulus and record the accommodation response in pilot studies and a detailed experiment, which has also been published elsewhere. It is found, among other things, that accommodation can respond to more than one different input level during its latency period, and that such inputs can be stored until components of the accommodation control system are free to process them. Indications of a minimum halting time for accommodation, of around 0.6 s, are presented. In later chapters, the development and testing of a new, binocular adaptive optics apparatus will be found. As well as binocular aberrometry and adaptive optics control of stimulus aberrations, this instrument displaces images to allow for and stimulate ocular convergence in binocular accommodation experiments. It is the first instrument in the world with its combined functionalities. Finally, the contribution of this thesis is summarised, and further instrumentation development and experiments are put forward for the continuation of this branch of accommodation and myopia research.

Various researchers have found that visual problems can contribute to clumsiness in children with DCD. One cause of motor development shortfalls that contribute to a DCD classification seems to be weak eye muscle functions. The visual system as well as well-developed eye muscle functions, play an important role in die development of balance, spatial orientation, body awareness and coordination (hand-eye, foot-eye, hand-foot-eye coordination). It also emerges from the literature that children with DCD do not usually outgrow their problems, although controversy still surrounds this aspect. The aim of this study was twofold. The first aim was to determine, as established by eye muscle functions, what the nature and scope of visual problems are, that is associated with DCD in 7 and 8 year-old children in Potchefstroom. The second aim was to determine whether 7 and 8 year-old Potchefstroom children will outgrow their DCD status without any motor intervention, and what the relationship between vision and the lasting effects of DCD status is. Thirty-two children (20 boys and 12 girls) with an average age of 95.66 months engaged in the study. During a follow-up study after a year of baseline testing at 83.33 months, the researcher wanted to determine whether the subjects diagnosed with DCD had possibly outgrown their DCD status. The Movement Assessment Battery for Children (MABC) (Henderson & Sugden, 1992) was applied for this purpose. The Sensory Input Screening Test (Pyfer, 1987), and the "Quick Neurological Screening Test" (QNST) (Mutti et al., 1998) test batteries were employed to determine the visual status of the children. The "Statistica for Windows 2008" computer software was used to analyse the data. Correlation coefficients as well as two-way variance tables were used for objective one to analyse the relationship between DCD and vision. The results confirmed correlations between DCD and eye muscle functions. Relationships were found between different eye muscle functions (fixation, visual pursuit, left and right eye, ocular alignment right eye) and the MABC total. Significant correlations, with small practical significance (p 10.2) was found between fine motor skills and fixation with both eyes, and with the left eye separately, visual pursuit with the right eye, as well as ocular alignment with the right eye, while a correlation with moderate practical significance (p 10.5) was found with fixtion with the right eye. All six eye muscle functions showed significant correlations with small practical significance (p 10.2) with ball skills. Static and dynamic balance also showed significant correlations with small practical significance (p 10.2) with fixation with both eyes, the left and right eye separately as well as with ocular alignment with the right eye. The results further indicated that in most cases where children have been diagnosed with serious DCD, they were classified in Class 3 (where more than three visual deviations occurred in the subject) regarding their vision. These percentages varied from 36.67% to 83.33%, with the highest percentage problems found in visual pursuit with the right eye. For objective 2, a dependent t-test was employed to determine the state of the children's DCD after a year has lapsed since diagnosis. The differences between the testing showed that most of the children have not outgrown their DCD status, but that the motor performance of a majority of the children has deteriorated over a period of one year (p 10.00). Furthermore, the percentage visual problems in the group with sustained DCD ranged from 71,87% - 100% (visual pursuit, fixation and ocular alignment), with the most visual problems found in fixation and visual pursuit skills. It can be concluded from the results that a significant relationship exists between DCD and a variety of visual functions, as determined by the different eye muscle functions. This evidence also indicated that most children will not outgrow their DCD status without any motor intervention programme. Intervention of children who are diagnosed with DCD should therefor include visual therapy.
Thesis (M.A. (Human Movement Science))--North-West University, Potchefstroom Campus, 2009.

The relationship between accommodation and myopia has been under investigation for many years, and the effort to understand it is ongoing. In this thesis, an introduction to the state of myopia research is given first, with particular reference to studies of accommodation and higher-order ocular aberrations, which feature in the subsequent chapters. Following a brief introduction to the general technique of aberrometry and visual stimulus control using adaptive optics, the development of a monocular adaptive optics instrument for this purpose is described. The instrument is used to vary a dioptric stimulus and record the accommodation response in pilot studies and a detailed experiment, which has also been published elsewhere. It is found, among other things, that accommodation can respond to more than one different input level during its latency period, and that such inputs can be stored until components of the accommodation control system are free to process them. Indications of a minimum halting time for accommodation, of around 0.6 s, are presented. In later chapters, the development and testing of a new, binocular adaptive optics apparatus will be found. As well as binocular aberrometry and adaptive optics control of stimulus aberrations, this instrument displaces images to allow for and stimulate ocular convergence in binocular accommodation experiments. It is the first instrument in the world with its combined functionalities. Finally, the contribution of this thesis is summarised, and further instrumentation development and experiments are put forward for the continuation of this branch of accommodation and myopia research.

The visual system and good ocular motor control play an important role in the effective development of gross motor, sport, fine motor and academic skills (Erhardt et al., 1988:84; Desrocher, 1999:36; Orfield, 2001:114). Various researchers report a link between ocular motor problems and attention–deficit hyperactivity disorder (ADHD) (Cheatum & Hammond, 2000:263; Farrar et al., 2001:441; Gould et al., 2001:633; Armstrong & Munoz, 2003:451; Munoz et al., 2003:510; Borsting et al., 2005:588; Hanisch et al., 2005:671; Mason et al., 2005:1345; Loe et al., 2009:432). A few studies were carried out to analyse the links between ADHD and ocular motor control with regard to matters like visual attention, visual perception and ocular motor control like eye movement outside the normal fixation point, but no studies have been reported on the status of the ocular motor control of South African populations, and the effect of visual–motor intervention on the ocular motor control or visual–motor integration of learners with ADHD. The aim of the study was twofold, namely firstly to determine the ocular motor control functions and status of visual–motor integration of a selected group of 6– tot 8–year–old learners with ADHD in Brakpan, South Africa, while the second aim was to determine whether a visualmotor– based intervention programme can improve the ocular motor control and status of the visual–motor integration of a selected group of 6– to 8–year–old learners with ADHD in Brakpan, South Africa. Statistica for Windows 2010 was used to analyse the data. The Sensory Input Screening measuring instrument and the Quick Neurological Screening Test II (QNST–II) were used to assess the ocular motor control functions (fixation, ocular alignment, visual tracking and convergence–divergence), while the Beery Developmental Test of Visual–Motor Integration (VMI–4de weergawe) was used to determine the status of the learners’ visual–motor integration (VMI), visual perception (VP) and motor coordination (MC). The Disruptive Behaviour Scale, a checklist for ADHD (Bester, 2006), was used as measuring instrument to identify the learners with ADHD. Fifty–six learners (31 boys, 25 girls, with an average age of 7,03 years +0,65) participated in the pre–test and were divided into an ADHD (n=39) and a non–ADHD (n=16) group for aim one. Two–way tables were used to determine the percentage of ocular motor control deficits in the learners with and without ADHD, and an independent t–test was used to analyse the visual–motor integration of these learners. The Pearson Chi–squared test was used to determine the practical significance of differences in VMI and VP (d>0,05). The results of the study reveal that the majority of learners displayed ocular motor control deficits, regardless of whether they were classified with ADHD or not. The biggest percentage of learners fell into Class 2 (moderate deficits), particularly with regard to horizontal (68,57%; 52,63%; w=0,16) and vertical tracking (65,71%; 73,68%), as well as convergence–divergence (80%; 78,95%; w=0,11). However, it appears that ADHD learners experience more serious problems (Class 3) with visual tracking than learners without ADHD (both eyes: 22,86%; compared to 10,53% (w=0,22); right eye: 11,43% compared to 0% (p=0,05; w=0,34); left eye: 14,29% compared to 0% (p=0,02; w=0,38)). Learners with and without ADHD displayed a practically significant difference with respect to visual perception (d=0,37) and motor coordination (d=0,5) compared to learners without ADHD (who achieved better results). For aim 2 the subjects were divided into three groups. A pre–test–post–test design compiled from an availability sample of three groups (intervention group with ADHD (n=20); control group with ADHD (n=10) and control group without ADHD (n=17)) was used for this part of the study. The intervention group participated in a nine–week (3x/week and for 45 minutes) visualmotor– based intervention programme in which the ocular motor control functions section was applied for about 5 minutes per learner. Forty–seven learners (25 boys and 22 girls) with an average age of 6,95 years (+0,69) constituted the experimental group, while a control group with ADHD with an average age of 7,2 years (+0,79) and a control group without ADHD with an average age of 7,12 years (+0,60) did not receive any intervention and just participated in the pre– and post–test opportunity. A two–way cross–tabulation table was used to determine the changes in ocular motor control functions. These results mainly revealed that practically significant changes occurred in all three groups, be it improvement or deterioration in the various classes of ocular motor control. It appears that as far as horizontal and vertical visual tracking is concerned, and with convergence–divergence, more subjects were moved back from Class 3 (serious cases) to Class 1 (no deficits) and 2 (moderate deficits) in particular than in the other two groups that had received no intervention. Independent t–testing was used to analyse intragroup differences in the visual–motor integration subdivisions, while a covariance analysis (ANCOVA) (corrected for pre–test differences) was used to determine adjusted average post–test difference values. These results revealed that the motor coordination of the intervention group improved more than that of the control group with ADHD (p=0,18). This can lead to the conclusion that the intervention programme did have an effect on this specific skill. Abstract The overall indications of the results are that learners with ADHD have a general tendency to achieve poorer results in ocular motor control tests and with skills involving visual–motor integration, visual perception and motor coordination than learners without ADHD. Although only a minor improvement was identified in the experimental group after participation in the intervention programme, it is recommended with regard to motor coordination in particular that a similar programme be compiled for ADHD learners that focuses more specifically on the ocular motor control needs of each learner, and that it be presented on a more individual basis in order to accomplish greater improvement.
Thesis (M.A. (Kinderkinetics))--North-West University, Potchefstroom Campus, 2012.

The visual system in humans provides the ability to interpret our surroundings from many distances. This complex system serves as a powerful sense which can drastically impact the quality of life when threatened or eliminated. While the mechanisms involved in visual interpretation are largely understood, many of the mechanisms of ocular diseases remain elusive. The most common ocular disorders are refractive errors, where failure of normal growth processes results in eye components with shape and sizes that are not matched to provide uncorrected sharp visual acuity without correction. Myopia, or nearsightedness, is a refractive error with prevalence rates of epidemic proportions in some urban Asian settings, and rising in other developed countries. Pathological, or high myopia, has an increased risk for potentially blinding ocular morbidities which can be irreversible and further negatively impact quality of life. Myopia, like other common ocular disorders, results from a combination of environmental and genetic factors. Over 20 candidate genomic regions have been identified as involved in myopic development progression.

One such locus, MYP3, on chromosome 12q21-23 spans nearly 44 Mb with more than 200 protein-encoding genes mapped within. Sizable candidate disease genomic regions typically require refinement to identify genes or variants within them which may contribute to disease development. Without an understanding of the underlying mechanistic framework of a disease, as is the case with myopia, biological inferences are difficult to make in prioritizing candidates, which can make finding true disease causing variants seem like finding a needle in a haystack. A better understanding of human ocular growth, as it relates to refractive error, may lead to more knowledgeable approaches to identifying the cause(s) of myopic development and associated ocular diseases.

To identify genes involved in ocular growth and development, whole genome expression patterns were assessed in human ocular tissues of fetal versus adult eyes, and adult posterior versus peripheral tissues. No database exists of fetal ocular tissue gene expression. In addition to providing insights into expression patterns during ocular development, these tissues were also compared as a surrogate to study rapid eye growth states such as in myopia. Only ocular tissue types with clinical phenotypes associated with myopic development were considered. Human retina/retinal pigment epithelium (RPE), choroid, sclera, cornea* and optic nerve* tissues were isolated from fetal (N=9; *N= 6) and adult (N=6) normal donor eyes. The Illumina® whole genome expression microarray platform was used to assess differential expression of genes. Fetal tissues were compared to their adult counterparts while adult posterior tissues were compared to their peripheral counterparts, and the differences in each were assessed using Ingenuity Pathway Analysis (IPA) for enriched functional groups and canonical pathways. Statistical significance for all tissue comparisons was determined using the Benjamin and Hochberg False Discovery Rate (FDR, 5%). Differentially expressed genes were compared to previously identified candidates for myopic development.

Additionally, qualitative and quantitative association studies in a large family (N=82) based high myopia cohort by genotyping 768 single nucleotide polymorphisms (SNPs) in the peak linkage area was performed to fine map the MYP3 linkage peak. Qualitative testing for high myopia (≤ -5 diopter (D) affected, > -5 D unaffected) and quantitative testing on the average (avg) dioptric sphere (SPH) was performed. Five candidate SNPs were genotyped in a replicate high myopia cohort for independent validation. Additionally, the most significant SNPs were screened in a previously genotyped twin cohort as a second independent validation cohort.

Ocular growth expression data were used to help prioritize the resulting association candidates as supporting evidence and was not used on its own to identify or exclude candidates. Candidate genes (within 100 kilobases (kb) of highly associated SNPs) identified through either qualitative or quantitative association testing were screened in the most disease relevant tissues (retina/ retinal pigment epithelium (RPE), choroid and sclera) for differential expression during ocular growth and by physical regions of the tissues within the eye. Genes that were identified by microarray studies as being differentially expressed in one or more tissue were validated using quantitative real time PCR (RT-qPCR).

Significant gene expression changes with fold changes > 1.5 were found in adult versus fetal retina/RPE (N=1185), choroid (N=6446), sclera (N=1349), and cornea (N=3872), but not the optic nerve nor any of the central versus peripheral tissues. In all adult versus fetal tissues, differentially expressed genes belonging to cancer, development, and cell death/growth functional groups, as well as signaling canonical pathways were enriched. Seventeen genes previously associated with increased susceptibility for non-syndromic high myopia were in the most significant functional assignments for at least one adult versus fetal ocular tissue. In adult central versus peripheral tissues, there was considerably more variation by tissue in enriched functions and canonical pathways of differentially expressed genes. The only functional category shared by all three tissue types was development.

MYP3 association testing yielded several genetic markers as nominally significant in association with high myopia in qualitative testing including rs3803036 (p=9.1X10-4), a missense mutation in PTPRR; and rs4764971 (p = 6.1X10-4), an intronic SNP in UHRF1BP1L. After correction for multiple testing, quantitative tests found statistically significant SNPs rs4764971 (p = 3.1x10-6), also found by qualitative testing; rs7134216 (p = 5.4X10-7), in the 31 UTR of DEPDC4; and rs17306116 (p < 9X10-4), intronic within PPFIA2. The intronic SNP in UHRF1BP1L, rs4764971, was validated for association with the quantitative trait of sphere (SPH) using an independently collected non-syndromic, high myopia cohort. SNPs within PTPRR (for quantitative association) and PPFIA2 (for qualitative and quantitative association) both approached significance in the independent high myopia cohort.

As with screening genes previously implicated in myopic development, qualitative and quantitative association candidates were screened in the independent whole genome expression array analyses, comparing normal rapidly growing fetal to normal grown adult ocular tissues. PTPRR and PPFIA2, candidates from qualitative and quantitative association respectively, were both validated by RT-qPCR with differential expression in at least one disease relevant ocular tissue. PTPRR and PPFIA2 belong to the same gene family- that of protein tyrosine phosphatase (PTP) genes. This family of genes relays extracellular signals that regulate cell growth, division, maturation and function, and its differential expression is consistent with our myopia surrogate model.

Many genes implicated in either syndromic or non-syndromic myopia were present in the most significantly enriched adult versus fetal functional and/or canonical pathways together. The adult versus fetal choroid and cornea tissue types had the most overlap with known non-syndromic myopic-associated genes in the most significantly enriched functional groups. Further exploration of the connections amongst these known genes may elucidate possible mechanistic roles for disease progression and/or reveal related novel candidate genes. Differentially expressed genes in central versus peripheral tissues yielded minimal overlap with genes implicated in myopia; however, in addition to broadening our understanding of the spatial variances in these tissues they may contain clues to the development and/or progression of other ocular diseases such as retinopathy of prematurity development.

The overlap with previously identified myopia-associated genes supports the model of eye growth for studying myopic development in human tissues. This expression data can be used both in prioritizing candidate genes other proposed genomic myopia loci, and also in detailed pathway analyses to identify potential biological mechanisms for candidates within these loci. Our most strongly associated candidate gene both in the discovery and replicate cohort was UHRF1BP1L, which was not differentially expressed in our data; however, interacting genes regulate the expression of at least one differentially expressed gene, indicating a possibly pathway connection. It is possible that differential expression may have been missed by the microarray data, or it may not be differentially expressed and affects myopic development through alternative or indirect means. While the expression data is a useful tool in prioritizing and inferring mechanistic roles for candidates, it cannot be used to exclude candidates. Deeper study of the pathways of candidate genes for myopic development may reveal connections to genes involved in ocular growth. Despite these potential limitations, two of the three novel candidates, PTPRR and PPFIA2, were supported by genomic convergence with the expression data, in addition to our discovery genetic association data. The other novel candidate, UHRF1BP1L, was validated in an independent Caucasian high-grade myopia cohort. Further validation and refinement of these three novel MYP3 candidate genes is necessary to make further claims about their possible involvement in myopic progression.

Dissertation