Some strains of coagulase-negative staphylococci produce an extracellular material, slime, which mediates adherence to foreign surfaces, such as indwelling biomedical devices. It is not known if slime is involved in adherence to human tissue. Coagulase-negative staphylococci are the most common members of normal ocular flora and cause many ocular infections, although the role of slime in these infections has not been studied.

Individuals who have Attention Deficit/Hyperactivity Disorder (ADHD) experience adverse effects relating to driving; in addition, they experience deficits in scanning ability (Barkely et.al, 1996; Fischer et al., 2007; Munoz et al., 2003; Naja-Raja et al., 2007). The present study examined the effects of ADHD on eye tracking while driving. Ten participants consisting of both ADHD and individuals who do not have ADHD were included in this study. It was hypothesized that individuals who have ADHD will make more saccadic eye movements and thus shorter fixations than individuals who do not have ADHD. Furthermore, it was hypothesized that despite the fact that individuals who have ADHD will make more saccadic eye movements than individuals without ADHD, those individuals with ADHD will commit more traffic violations including collisions compared to individuals who do not have such a diagnosis. Findings indicated that hypothesis one was not supported by the data, whereas hypothesis two was supported in that ADHD individuals had more collisions and committed more traffic violations than the Control group. Additionally, upon conducting a Chi Square test for independence, a significant difference was found in the spatial distributions of the fixations between the ADHD and Control groups. The findings of this study could help better understand the factors involved in ADHD driving and could be used to train individuals with ADHD to become more aware of their surroundings and driving habits and thus become safer drivers.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Las dificultades del aprendizaje se cuentan entre las principales razones de la deserción escolar, siendo éste un problema a nivel global. El diagnóstico temprano de estas dificultades es primordial para abordar un tratamiento de manera temprana y un acompañamiento adecuado. Hoy en día el diagnóstico de estas dificultades se lleva a cabo por psicopedagogos y/o psicólogos evaluando la resolución de una batería de tests. La relación 1 a 1 entre una persona a diagnosticar y el profesional dificulta la tarea de estudios masivos para detectar tempranamente a niños en edad escolar que sufran alguna dificultad específica del aprendizaje. Un síntoma estudiado para detectar procesos cognitivos anómalos son comportamientos atípicos en los movimientos oculares. Con la tecnología de acceso masivo se pueden registrar los movimientos oculares, de manera sencilla y económica, con dispositivos de seguimiento ocular llamados por su nombre en inglés eye trackers. En esta tesis se desarrollaron herramientas para el estudio de las señales de los dispositivos mencionados. Una de estas herramientas es clave para estudiar los movimientos oculares y es la clasificación de estos en dos grandes grupos llama- dos fijaciones y sacadas. Las características estadísticas que poseen estos movimientos están íntimamente relacionados con procesos cognitivos. Otra herramienta desarrolla- da es el cálculo de diferentes cantidades de carácter estadístico que permiten describir en pocos números múltiples propiedades de señales obtenidas con los eye trackers. Una dificultad específica del aprendizaje que padece alrededor del 10 % de la población es la dislexia. Ésta es un trastorno con el que, aún hoy, hay controversia al momento de definirlo, pero que es una dificultad que afecta el desarrollo el desarrollo de la alfabetización y las habilidades relacionadas con el lenguaje. En esta tesis se estudiaron los movimientos oculares de niños que fueron diagnosticados con dislexia y de niños de un grupo control que han tenido un desarrollo típico. Describimos la dinámica de la trayectoria de la mirada de los niños al leer con un modelo estocástico basado en lo que se conoce como Continuous Time Random Walk (CTRW). Con dicho modelo fuimos capaces de generar señales sintéticas con iguales características que las señales reales. La generación de señales sintéticas es una técnica clave en el aprendizaje automático, o aprendizaje de máquina (machine learning) y es importante porque ayuda a mejorar el rendimiento de los modelos, combatir el sobre-ajuste y manejar la escasez de datos. Con datos reales hemos probado una serie de clasificadores de disléxicos y no disléxicos utilizando herramientas de machine learning. Dos de estos métodos tuvieron una alta precisión. Tener herramientas para analizar movimientos oculares podría ayudar en el diagnóstico rápido de dificultades del aprendizaje. A su vez podría ayudar a evaluar de forma masiva a niños en sus colegios y así bajar de forma drástica la deserción escolar. / Learning difficulties are among the main reasons for school dropout, this being a global problem. The early diagnosis of these difficulties is essential to address early treatment and adequate follow-up. Today the diagnosis of these difficulties is carried out by educational psychologists and/or psychologists evaluating the resolution of a battery of tests. The 1 to 1 relationship between a person to be diagnosed and the professional makes the task of massive studies difficult to detect early school-age children who suffer from a specific learning difficulty. A symptom studied to detect abnormal cognitive processes are atypical behaviors in eye movements. With mass access technology, eye movements can be recorded easily and cheaply with eye tracking devices. In this thesis, tools were developed to study the signals of the mentioned devices. One of these tools is key to studying eye movements and it is the classification of these into two large groups called fixations and saccades. The statistical characteristics that these movements have are closely related to cognitive processes. Another tool developed is the calculation of different quantities of a statistical nature that allow multiple properties of signals obtained with eye trackers to be described in a few numbers. A specific learning difficulty that about 10 % of the population suffers from is dyslexia. This is a disorder with which, even today, there is controversy when defining it, but it is a difficulty that affects the development of literacy and language-related skills. In this thesis, the eye movements of children who were diagnosed with dyslexia and of children from a control group who have had a typical development were studied. We describe the dynamics of children’s gaze trajectory when reading with a stochastic model based on what is known as Continuous Time Random Walk (CTRW). With this model we were able to generate synthetic signals with the same characteristics as the real signals. The generation of synthetic signals is a key technique in machine learning, or machine learning, and is important because it helps improve model performance, combat overfitting, and handle data sparseness. With real data we have tested a series of dyslexic and non-dyslexic classifiers using machine learning tools. Two of these methods had high precision. Having tools to analyze eye movements could help in the rapid diagnosis of learning difficulties. In turn, it could help to massively evaluate children in their schools and thus drastically reduce school dropouts, with all the benefits that this entails for society.

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Over 2.4 million eye injuries occur each year in the United States as a result of trauma. Eye injuries have been investigated for years; however, the role of the extraocular muscles in relation to eye injuries has yet to be quantified. In this research, Computed Tomography quasi-static tests were conducted to investigate the effect of the presence of the extraocular muscles on the biomechanical response of the human eye in situ. Three matched pairs of human eyes were displaced in 5 mm increments using a large flat cylindrical indenter to a maximum displacement of 30 mm. The loading was similar to what is experienced during a blunt impact, which is believed to cause the most serious eye injuries. In the matched pair, one eye had the extraocular muscles intact and the other had the extraocular muscles transected. Force, pressure, and displacement measurements were collected for each test. A trend was seen where a greater amount of force was created in the eye with the extraocular muscles intact than in the eye with the muscles transected, and a correlation between them was made. The greatest force measured in an eye with the extraocular muscles intact was 92 N, while the greatest force measured in an eye with the extraocular muscles transected was 80 N. An increase in intraocular pressure was also noticed for an eye with the extraocular muscles attached, rising steadily from 2 kPa to a maximum pressure of just over 50 kPa. It was also noted that during a quasi-static impact the eye can move out of the way of the imposing force. Since the test data set was small, analytical calculations were also conducted. / Master of Science