View clinical trials related to Vision.
Filter by:The ability to judge the locations of various objects from oneself during self-motion in the intermediate distance range (~2-25m) is crucial for successful performance of activities of daily living, such as walking and driving. However, little is known about the mechanisms of visual space perception involved in judging distance, the focus of this project, in the planning and/or execution of self-motion in the natural 3D environment. The theoretical knowledge to be gained from this project will contribute to the scientific literature and provide insights into how eye and neurological defects could impair visual space perception, wayfinding, and mobility.
When looking at an x-ray, radiologists are typically asked to localize a tumor (if present), and to classify it, judging its size, class, position and so on. Importantly, during this task, radiologists examine on a daily basis hundreds and hundreds of x-rays, seeing several images one after the other. A main underlying assumption of this task is that radiologists' percepts and decisions on a current X-ray are completely independent of prior events. Recent results showed that this is not true: perception and decisions are strongly biased by past visual experience. Although serial dependencies were proposed to be a purposeful mechanism to achieve perceptual stability of otherwise noisy visual input, serial dependencies play a crucial and deleterious role in the everyday task performed by radiologists. For example, an x-ray containing a tumor can be classified as benign depending on the content of the previously seen x-ray. Given the importance and the impact of serial dependencies in clinical tasks, in this proposal, the investigators plan to (1) establish, (2) identify and (3) mitigate the conditions under which serial effects determine the participants' percepts and decisions in tumor search tasks. In Aim 1, the investigators will establish the presence of serial effects in four different clinically relevant domains: tumor detection, tumor classification, tumor position and recognition speed. In Aim 2, the investigators plan to identify the specific boundary conditions under which visual serial dependence impacts tumor search in radiology. In Aim 3, once the investigators fully understand these boundary conditions in Aim 2, they will propose a series of task and stimulus manipulations to control and mitigate the deleterious effects of visual serial dependence on tumor search. As a result of these manipulations, visual search performance should improve in measurable ways (detection, classification, position, speed). Aim 3 is particularly crucial because it will allow the investigators to propose new guidelines which will greatly improve tumor recognition in x-ray images, making this task even more effective and reliable. Taken together, the proposed studies in Aim 1, 2, and 3 will allow the investigators to establish, identify, and mitigate the deleterious effect of serial dependencies in radiological search tasks, which could have a significant impact on the health and well-being of patients everywhere.
During visual fixation, small eye movements of which we are usually not aware, prevent the maintenance of a steady direction of gaze. These eye movements are finely controlled and shift retinal projection of objects within the fovea, the region of the retina where visual acuity is highest. This program of research examines the link between these eye movements and attention, and tests the hypothesis that attention, similarly to eye movements, can be controlled at the foveal level. Psychophysical experiments with human subjects, using state-of-the-art techniques, high resolution eyetracking and retinal stabilization are conducted to address these questions. Gaze-contingent calibration procedures are employed to achieve high accuracy in gaze localization. A custom developed gaze-contingent display is used to shift in real-time visual stimuli on the monitor to compensate for the observer eye movements during fixation periods and to maintain stimuli at a desired location on the retina. Experiments involve visual discrimination/detection tasks with stimuli presented at selected eccentricities within the fovea. Participants' performance and reaction times are examined under different conditions, in which various types of attention are manipulated. In addition to advancing our basic understanding of visual perception, this research leads to a better understanding of attentional control at the foveal scale and of the contribution of microscopic eye movements to the acquisition and processing of visual details.
The aim of this study is to collect data on the early visual development of extreme premature infants. The method is the measurement of flash visual evoked potentials and the study population includes premature infants under the 28th weeks of gestation, who have normal cranial ultrasound examinations, normal aEEG, no clinical neurological symptoms and who have a normal ophthalmological status. fVEP measurements were recorded from the first week of life every second week until term. The fVEP recordings were performed in active sleep, in stable premature infants, who were continuously monitored. The Nihon Kohden Neuropack 8 was used, the stimulus frequency was 0,5 Hz, artefact free averages were analyzed. The measurements were analyzed according to the presence and absence of known waveforms, their latencies and amplitudes. Longitudinal analysis was performed to analyse the effect of extrauterine visual development on fVEP with growing gestational ages.