Dissertations / Theses on the topic 'Eye Movement Measurements'

Clinicians are becoming increasingly aware of the effect of various pathologies on the characteristics of saccadic eye movements. As such, an efficient and non-invasive means of measuring eye-movement in a clinical environment is of interest to many. The aim of this thesis is to investigate the clinical application of a non-invasive eye movement recording technique as a part of a clinical examination. Eye movements were measured using an IRIS 6500 infrared limbal eye tracker, which we customized for the direct recording of oblique eye movements as well as horizontal and vertical. Firstly, the eye-tracker itself was assessed. Visually normal observers made saccadic eye movements to a 10' stimulus in eight directions of gaze. Primary (ANOVA) and secondary analyses (mean error less than 5%) resulted in acceptance that averaging four measurements would give a representative measurement of saccadic latency, peak velocity, amplitude and duration. Test-retest results indicated that this technique gives statistically (± 1.96*STDEVDifference) repeatable responses. Several factors that could potentially influence clinically based measures of eye-movements were examined. These included, the effect of ageing, viewing distances, dioptric blur and cataract. The results showed that saccadic latency and duration are significantly (p < 0.05) longer in older (60-89 years) observers compared to younger (20-39 years). Peak velocity and amplitude were not significantly affected by the age of the observer. All saccadic parameters (SP) were significantly affected by direction (Chapter 5). The compact nature of this eye movement methodology is obtainable since there is no significant effect on viewing distance (300 cm vs. 49 cm) (Chapter 6). There is also no significant effect of dioptric blur (up to +LOODS) on any of the four SP. In contrast, a higher level of defocus (+3.O ODS) has a larger probability of interfering with the measurements of peak velocity and duration (Chapter 7). Saccadic eye-movements were also recorded whilst normally sighted subjects wore cataract simulation goggles. The results suggested that the presence of dense cataract introduces significant increases in saccadic latencies and durations. No effect was found on the peak velocities and amplitudes. The effect of amblyopia on SP was also investigated in order to examine if this methodology is able to detect normal from abnormal responses (i.e. increased saccadic latencies). This set of data (Chapter9 ) showed that using IRIS 6500, longer than normal latencies may be recorded from the amblyopic eye but no consistent effect was found for the other SP (peak velocity, amplitude, duration). Overall, the results of this thesis demonstrate that the IRIS 6500 eye-tracker has many desirable elements (it is non-invasive; comfortable for the observers and gives repeatable and precise results in an acceptable time) that would potentially make it a useful clinical tool as a part of a routine examination.

Saccadic and vestibular-evoked eye movements are similar in that their three-dimensional kinematic properties show eye position-dependence. When the line of sight is directed towards an eccentric target, the eye velocity axis tilts in a manner that depends on the instantaneous position of the eye in the head, with the magnitude of tilt also depending on whether the eye movement is saccadic or vestibular-evoked. The mechanism responsible for producing eye velocity axis tilting phenomena is not well understood. Some authorities have suggested that muscle pulleys in the orbit are critical for implementing eye velocity axis tilting, while others have suggested that the cerebellum plays an important role. In the current study, three-dimensional eye and head rotation data were acquired, using the magnetic search coil technique, to confirm the presence of eye position-dependent eye velocity axis tilting during saccadic eye movements. Both normal humans and humans with cerebellar atrophy were studied. While the humans with cerebellar atrophy were noted to have abnormalities in the two-dimensional metrics and consistency of their saccadic eye movements, the eye position-dependent eye velocity axis tilts were similar to those observed in the normal subjects. A mathematical model of the human saccadic and vestibular systems was utilized to investigate the means by which these eye position-dependent properties may arise for both types of eye movement. The predictions of the saccadic model were compared with the saccadic data obtained in the current study, while the predictions of the vestibular model were compared with vestibular-evoked eye movement data obtained in a previous study. The results from the model simulations suggest that the muscle pulleys are responsible for bringing about eye position-dependent eye velocity axis tilting for both saccadic and vestibular-evoked eye movements, and that these phenomena are not centrally programmed.

Master of Science in Medicine
Saccadic and vestibular-evoked eye movements are similar in that their three-dimensional kinematic properties show eye position-dependence. When the line of sight is directed towards an eccentric target, the eye velocity axis tilts in a manner that depends on the instantaneous position of the eye in the head, with the magnitude of tilt also depending on whether the eye movement is saccadic or vestibular-evoked. The mechanism responsible for producing eye velocity axis tilting phenomena is not well understood. Some authorities have suggested that muscle pulleys in the orbit are critical for implementing eye velocity axis tilting, while others have suggested that the cerebellum plays an important role. In the current study, three-dimensional eye and head rotation data were acquired, using the magnetic search coil technique, to confirm the presence of eye position-dependent eye velocity axis tilting during saccadic eye movements. Both normal humans and humans with cerebellar atrophy were studied. While the humans with cerebellar atrophy were noted to have abnormalities in the two-dimensional metrics and consistency of their saccadic eye movements, the eye position-dependent eye velocity axis tilts were similar to those observed in the normal subjects. A mathematical model of the human saccadic and vestibular systems was utilized to investigate the means by which these eye position-dependent properties may arise for both types of eye movement. The predictions of the saccadic model were compared with the saccadic data obtained in the current study, while the predictions of the vestibular model were compared with vestibular-evoked eye movement data obtained in a previous study. The results from the model simulations suggest that the muscle pulleys are responsible for bringing about eye position-dependent eye velocity axis tilting for both saccadic and vestibular-evoked eye movements, and that these phenomena are not centrally programmed.

Application of eye movement measurement is especially significant in Neuroscience. Results from eye tracking can give valuable insight into the correlation between neural activity and eye movements. Abnormalities in the eye movements also provide information regarding diagnosis and progress of neurological diseases such as dementia. Another application is in developing human-computer interfaces as a means of communication for the severely handicapped. Although there are numerous eye tracking techniques available, the magnetic search coil method has been prominently used by researchers due to its high accuracy and precision. This technique typically requires the subjects head to be fixed for accurate measurements due to the use of large field coils. Here we propose a miniaturized coil system using MEMS technology for application in eye movement measurement. The coils were designed and modeled using CoventorWare and MagNet software. The microcoils were then fabricated in the McGill Nanotools microfabrication laboratory. We present the results for using the materials Indium Tin Oxide (ITO) and Aluminium for the fabrication of coils. We found that the resulting coil system is capable of identifying displacements along the X, Y and Z axis. The resolution of the system depends on the configuration of the system, it was calculated to be around 20-40 μm on the plane of the coil and it increases near the centre of the coil. Although the proposed coil system holds significant potential, but further exhaustive testing needs to be performed in an environment simulating eye movements.
O Mesurer avec précision les mouvements oculaires constitue un élément essentiel dans ledomaine de la neuroscience. Par exemple, capter les mouvemets de l'oeil contribue à la compréhension de la relation entre les activités neuronales et le comportement oculaire. De meme, les irrégularités observées dans les mouvements des yeux aident à diagnostiquer et à surveiller le progrès de plusieurs troubles mentaux comme la démence. En plus, le tracement de la trajectoire oculaire peut être utilisé pour construire des interfaces homme-machine pour les personnes sévèrement handicapées.Bien que plusieurs techniques de tracement oculaire existent déjà, la bobine de recherche magnétique est fortement utilisée par les chercheurs. Elle offre une haute exactitude et une très bonne précision de mesure. La technique traditionnelle exige l'utilisation de grandes bobines de champs, nécessitant ainsi que la tête du sujet soit fixée en tout temps. En revanche, on propose l'utilisation d'un système de bobines miniaturisées construit avec la technologie MEMS. Les bobines ont été conçues à l'aide des logiciels CoventorWare et MagNet. Les micro-bobines ont été fabriquées dans le laboratoire de micro-fabrication Nanotools de l'Université McGill. On présente les résultats obtenus en utilisant des micro-bobines construites avec la solution solide de l'oxyde de l'étain et l'oxyde de l'indium (ITO). Le système de micro-bobine est capable d'identifier les déplacements dans les trois dimensions X, Y, et Z. La résolution du système dépend de la configuration utilisée. On a trouvé que la résolution peut être entre 20 et 40 μm. Le système proposé est très promettant mais plusieurs tests exhaustifs deraient encore être appliquées dans des environnements qui simulent de vrais mouvements oculaires.

In the first years of life, there is a dramatic unfolding of cognitive abilities supported by the progressive control of gaze behaviour. The early development of oculomotor control is presumably closely tied to the maturation of the attention system. Vergence eye movements are the movements of the eyes in opposite directions, which subserve binocular vision and depth perception. Previous studies have suggested a correlation between vergence and orienting attention (Puig, Pallarés, Zapata, & Puigcerver, 2016; Solé Puig, Pérez Zapata, Aznar-Casanova, & Supèr, 2013; Super, Marco, Perez Zapata, Canete Crespillo, & Sole Puig, 2014). The neural structures involved in the vergence system, for instance the Frontal Eye Fields (FEF), Superior Colliculus (SC), pulvinar of the thalamus and Posterior Parietal Cortex (PPC) overlap with those of the attention orienting system. This is of relevance as studying how children allocate their visual attention to relevant stimuli is a direct measure of cognitive abilities. Vergence has been studied in our research group as a measure of cognitive processing (e.g. Sole Puig et al., 2013, 2015, 2016; Esposito et al., 2018, 2019; Varela et al., 2018). In these studies, vergence responses were observed during top-down and bottom-up generated shifts of visual attention, where attentional load positively correlated with the strength of the vergence response (Sole Puig et al., 2013). The notion of a role for vergence in attention is supported by the observation of a correlation of eye vergence responses with the neural activity encoding shifts of visual attention (Solé Puig et al., 2016). Besides attention, vergence relates to memory processing as well. Memorized stimuli are accompanied with stronger vergence responses when compared to stimuli that are forgotten (Sole Puig et al., 2016). These observations motivated our current studies in younger children, to contribute to a better understanding on the impact of vergence eye movements in cognitive development early on. This PhD study consists exploring the association between the changes in the angle of vergence eye movements’ and orienting attention responses in early childhood. With eye tracking methodology, Face perception and Visual Short-Term Memory (VSTM) were evaluated as fundamental milestones of cognitive development. 130 young children aged 6-36 months were recruited from two regional kindergartens. Face images versus scrambled face images on one hand, and repeated objects versus novel objects’ images on the other hand, were introduced as visual presentations, to tackle basic cognitive functions that we hypothesize are based on orienting attention. The first study addressed face processing. A series of prototypical static human face images with neutral expression were presented from a validated face database and compared it with their computerized scrambled version. We observed that vergence eye movements’ responses were enhanced to face stimuli when compared to scrambled face stimuli. The study on Visual Short-Term Memory contends with the ability to temporarily hold information and form transient representations of objects. In turn, establish whether children utilize this visual information to anticipate future events. We presented two coloured objects on screen and randomly repeated one of them and a novel one separately. We observed that for the repeated object presentation, not only did vergence response increase, but also the order of image type correlated with the enhancement in vergence modulation. Thus far, to the best of my knowledge, this is the first PhD study of its type evaluating vergence eye movements to assess attention-orienting responses in early childhood.
En los primeros años de vida existe un gran despliegue de habilidades cognitivas respaldado por el control progresivo de la mirada. El desarrollo temprano del control oculomotor está asociado al desarrollo de la atención. Los movimientos oculares de vergencia consisten en el movimiento de los ojos en direcciones opuestas que dan lugar a la visión binocular y la percepción de profundidad. Previamente, hemos sugerido una correlación entre la vergencia y la orientación de la atención (Puig et al., 2016; Solé Puig et al., 2013; Super et al., 2014). Las estructuras neuronales involucradas en el sistema de vergencia, entre ellas, los campos oculares frontales, el colículo superior, el pulvinar del tálamo y la corteza parietal posterior se superponen con las del sistema de orientación de la atención. Esto es relevante ya que el estudio de cómo los niños despliegan y distribuyen su atención visual a los estímulos relevantes del entorno es una medida directa de sus capacidades cognitivas. De este modo, la orientación de la atención puede arrojar luz sobre el desarrollo cognitivo a posteriori. La vergencia ha sido estudiada en nuestro grupo de investigación como una medida del procesamiento cognitivo (Sole Puig et al., 2013, 2015, 2016; Esposito et al., 2018, 2019; Varela et al., 2018). En estos estudios, se observaron respuestas de vergencia durante los cambios en la atención visual generados de arriba hacia abajo y de abajo hacia arriba, donde la carga atencional correlacionó positivamente con la amplitud en la respuesta de vergencia (Sole Puig et al., 2013). La noción de un papel de la vergencia en la atención se basa en la observación de una correlación en las respuestas de vergencia ocular con la actividad neuronal que codifica los cambios en la atención visual (Solé Puig et al., 2016). Asimismo, la vergencia está relacionada con la memoria. Los estímulos memorizados se ven reflejados en respuestas de vergencia más pronunciadas en comparación con los estímulos no retenidos en la memoria (Sole Puig et al., 2016). Este estudio doctoral consiste en explorar la asociación entre la modulación en el ángulo de vergencia y la orientación de la atención en la infancia. Mediante la metodología de seguimiento ocular, el procesamiento de caras y la memoria visual a corto plazo (MVCP) se evaluaron como hitos fundamentales del desarrollo cognitivo. Se reclutaron 130 niños de 6 a 36 meses de edad de 2 jardines de infantes regionales. Por un lado, presentamos imágenes de caras frente a imágenes de puzles de caras, y en la otra tarea, imágenes de objetos repetidos frente a objetos nuevos. El primer estudio abordó el procesamiento facial. Una serie de imágenes estáticas prototípicas de caras humanas con expresión neutral se compararon con su versión computarizada. Observamos que las respuestas de vergencia aumentaron frente a los estímulos de caras en comparación con los estímulos de puzles de caras. Por otra parte, el estudio sobre la memoria visual a corto plazo tiene relación con la capacidad de mantener temporalmente la información y formar representaciones transitorias de objetos. Asimismo, queríamos observar si los niños utilizan esta información visual para anticipar eventos futuros. Para ello, presentamos simultáneamente dos objetos de colores en la pantalla y luego repetimos uno al azar y otro nuevo, por separado. Hemos observado un incremento en la modulación de la vergencia en el caso de los objetos repetidos y asimismo correlacionado el incremento en la vergencia con el orden de presentación de la imagen. Este es el primer estudio doctoral de su tipo que proporciona información novedosa acerca de la vergencia para evaluar las respuestas de orientación de la atención visual en la primera infancia.

No
Language is more than a source of information for accessing higher-order conceptual knowledge. Indeed, language may determine how people perceive and interpret visual stimuli. Visual processing in linguistic contexts, for instance, mirrors language processing and happens incrementally, rather than through variously-oriented fixations over a particular scene. The consequences of this atypical visual processing are yet to be determined. Here, we investigated the integration of visual and linguistic input during a reasoning task. Participants listened to sentences containing conjunctions or disjunctions (Nancy examined an ant and/or a cloud) and looked at visual scenes containing two pictures that either matched or mismatched the nouns. Degree of match between nouns and pictures (referential anchoring) and between their expected and actual spatial positions (spatial anchoring) affected fixations as well as judgments. We conclude that language induces incremental processing of visual scenes, which in turn becomes susceptible to reasoning errors during the language-meaning verification process.

碩士
國立台灣工業技術學院
管理技術研究所
85
The current research designed an experiment to investigate the effects on three important task factors in dynamic visual information presentation on mental workload as reflected in the eye movement parameters. Ten subjects tracked the scanning line at two different speeds. They were required to respond to a designed targets presented at two different frequency. The difficulty of the reaction time task was manipulated by the difference between a simple reaction task and a physical match task. Reaction time, pupil diameter and eye movement speed were collected to observed the impacts of three important task factors to the human information processing load. The result proved that reaction time was significantly affected by the task difficulty and target presentation frequency while eye movement speed was affected by the tracking speed and target presentation frequency. The magnitude of increase and curve amplitude and standard deviation of the pupil diameter can partially explain the increase in information processing load due to increase in eye movement speed.Keyword: mental load, eye movement speed, pupil diameter

Thesis (M.A.)--York University, 2006. Graduate Programme in Psychology.
Typescript. Includes bibliographical references (leaves 50-52). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR29608

Mental workload is commonly defined as the proportion of a person's total mental capacity in use at a given moment. A measure of mental workload would have utility in a number of rehabilitation medicine applications, but no method has been adequately examined for these purposes. A candidate measure is the intersaccadic interval (ISI), which is the duration between two successive saccades. Previous studies indicate that ISI length may be linked to mental workload, but this link is poorly understood for tasks that are not primarily visual. Therefore, the current study was an investigation of ISI and workload intensity in three non-visual tasks: mental arithmetic, verbal fluency, and audio perception. Workload was manipulated through changes in task difficulty as well as study participant motivation level. An analysis of eye movements and other experimental workload measures indicated a significant association between audio perceptual workload and ISI length.

碩士
國立成功大學
電機工程學系碩博士班
94
In the busy society, a lot of pressures may induce people's sleep-disorder, which may in turn influence the personal health, decrease working efficiency reduce and consume much more medical resource. Gradually, the sleep-disorder has been the focus that everybody paid attention to. So, it is important to design one kind of simple and effective sleep evaluation system to offer the doctor or researcher a primary data or provide people to use at home. In this thesis, we adopt the signals of Rapid-Eye Movements as measurand, and measure them by a self-designed modularized hardware. Then the measured REM signals are sent through an USB-6009 type data acquisition card to personal computer for displaying and storage. Finally, we study the relationship between sleep and Rapid-Eye Movements by analyzing the acquired data with LabVIEW-based graphical program.

No
The eye rotation approach for measuring peripheral eye length leads to concern about whether the rotation influences results, such as through pressure exerted by eyelids or extra-ocular muscles. This study investigated whether this approach is valid. Peripheral eye lengths were measured with a Lenstar LS 900 biometer for eye rotation and no-eye rotation conditions (head rotation for horizontal meridian and instrument rotation for vertical meridian). Measurements were made for 23 healthy young adults along the horizontal visual field (+/- 30 degrees ) and, for a subset of eight participants along the vertical visual field (+/- 25 degrees ). To investigate the influence of the duration of eye rotation, for six participants measurements were made at 0, 60, 120, 180 and 210 s after eye rotation to +/- 30 degrees along horizontal and vertical visual fields. Peripheral eye lengths were not significantly different for the conditions along the vertical meridian (F1,7 = 0.16, p = 0.71). The peripheral eye lengths for the conditions were significantly different along the horizontal meridian (F1,22 = 4.85, p = 0.04), although not at individual positions (p >/= 0.10) and were not important. There were no apparent differences between the emmetropic and myopic groups. There was no significant change in eye length at any position after maintaining position for 210 s. Eye rotation and no-eye rotation conditions were similar for measuring peripheral eye lengths along horizontal and vertical visual field meridians at +/- 30 degrees and +/- 25 degrees , respectively. Either condition can be used to estimate retinal shape from peripheral eye lengths.

Indiana University-Purdue University Indianapolis (IUPUI)
Stroke is the main cause of disability in the United States. Individuals with stroke commonly report sensory impairment affects their recovery. Motor recovery and sensory impairment are related and impact individuals’ ability to perform valued occupations. Despite the prevalence of sensation impairment after stroke, many occupational therapists fail to include sensation assessment and intervention in treatment planning. The exclusion of sensation in occupational therapy interventions during stroke rehabilitation may be due to the lack of literature supporting the association between sensation and occupational performance. The current study aimed to determine the relationship between touch sensation of the affected hand and occupational performance and satisfaction in individuals with chronic stroke. Using a cross-sectional study design, this study associated factors related to hand sensation and function in individuals with chronic stroke. Fifty individuals with chronic stroke participated in a one-time testing session in which assessments related to sensation, movement of the hand and engagement in daily activities were administered. Correlation analyses were utilized to determine relationships between touch sensation of the affected hand with individuals’ abilities to engage in valued daily activities, arm and hand disability, and manual abilities. The main finding of the study was that individuals with intact sensation reported greater ability to perform valued occupations and satisfaction with their performance, as compared with individuals with touch sensation impairment. For individuals with impaired touch sensation of the affected hand, impairment of touch sensation of the hand did not correlate with individuals’ performance or satisfaction with valued occupations, arm or hand movement, or manual abilities. Collectively, the results of this study reflect the complex interaction between touch sensation, occupational performance, motor functioning, and manual abilities of the affected hand for individuals’ who have experienced a stroke. This study informs therapists, rehabilitation scientists, and other healthcare professionals that client-centered, individualized approaches, including a wide array of clinical assessments and intervention, including assessment of occupational performance and sensation, remain important components in stroke rehabilitation.