no / This study aimed to determine if response times gathered during perimetry can be exploited within a thresholding algorithm to improve the speed and accuracy of the test. Frequency of seeing (FoS) curves were measured at 24 locations across the central 30° of the visual field of 10 subjects using a Method of Constant Stimuli, with response times recorded for each presentation. Spatial locations were interleaved, and built up over multiple 5-min blocks, in order to mimic the attentional conditions of clinical perimetry. FoS curves were fitted to each participant’s data for each location, and response times derived as a function of distance-from-threshold normalised to the slope of each FoS curve. This data was then used to derive a function for the probability of observing response times given the distance-from-threshold, and to seed simulations of a new test procedure (BURTO) that exploited the probability function for stimulus placement. Test time and error were then simulated for patients with various false response rates. When compared with a ZEST algorithm, simulations revealed that BURTO was about one presentation per location faster than ZEST, on average, while sacrificing less precision and bias in threshold estimates than simply terminating the ZEST earlier. Despite response times varying considerably for a given individual and their thresholds, response times can be exploited to reduce the number of presentations required in a visual field test without loss of accuracy.

Many systems today do not allow the operator to view the environment directly. For example, operators of telerobotic or remote manipulation systems may be far removed from the work site. In these situations, images from cameras at the task site provide the only visual link between the task and operator. Such imaging systems are unable to provide exact representations of the task environment, resulting in a possible degradation of important visual cues. If visual cues are degraded, task performance may be less accurate, require increased completion time, and subject the operator to hazardous conditions. In this study, the field of view and contrast of imagery were manipulated to determine their effects on observers' ability to estimate distances of targets within natural settings. Images were video taped with a rotating camera and the targets were placed between 9.14 m and 60.96 m from the camera. The fields of view ranged from 20 deg to 74 deg. A lightly wooded area and an open field were used to provide either high or low visual contexts, respectively. Participants rated their confidence in the distance estimates on a seven-point scale. / Master of Science

A large number of studies in psychology and cognitive neuroscience suggest that the left and right cerebral hemispheres have differences in specialization of processing. The left hemisphere tends to be specialized for complex capacities such as language and numbers, whereas the right hemisphere typically shows advantages for visuospatial attention and recognition of nonverbal form. The present study was designed to investigate whether these functional cerebral asymmetries would extend to working memory tasks. It was hypothesized that the left hemisphere would have more advantage for accurate responses to a Number-based memory task, whereas the right hemisphere would be relatively advantaged for accurate responses on a Color-based memory task. For the Color-based memory task, we used a Corsi-Block memory task (4x4 grid). For the Number-based memory task, we used a string of 8 digits. In each case, to-be-remembered stimuli were constructed sequentially, such that participants (N = 39) had to form and maintain the image in working memory. Participants then compared these remembered stimuli with flashed images that appeared either on the left or right edge of the screen. We recorded the correct responses and the response time. The left hemisphere appears to be advantaged for accurate responses when the memory stimuli are numerical in nature, whereas the right hemisphere has more advantage for accurate responses on the color-memory task.

Licentiatavhandling (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 2 uppsatser.

Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2006. / Vita. Includes bibliographical references (leaves 161-176).

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 229-239).

Qui n’a jamais souhaité avoir des yeux derrière la tête ? Cette thèse propose d’étudier l’extension du champ visuel humain, que ce soit dans le monde réel ou dans un environnement virtuel. Nous avons d’abord conçu FlyVIZ, un dispositif qui permet d’augmenter le champ visuel. Il est composé d’une caméra catadioptrique, d’un visiocasque et d’un algorithme de traitement d’image. Lorsqu’un utilisateur porte ce dispositif, il dispose d’une vue à 360 degrés de son environnement. Le prototype a été testé avec succès dans différents scenarios, comme attraper un objet tendu dans le dos sans tourner la tête, ou passer des portes en marchant à reculons. Ensuite nous avons proposé une nouvelle méthode pour le rendu d’environnements virtuels, avec un champ visuel étendu, et en temps réel. Pour résoudre les problèmes dus à l’utilisation de projections non planes, nous avons ajouté une nouvelle étape dans le pipeline graphique. Notre méthode a ensuite été adaptée au rendu stéréoscopique avec un champ visuel de 360°. Nous avons mené une évaluation préliminaire sur l’utilisation d’un champ visuel étendu appliqué à une tache de navigation dans des environnements virtuels. Nos résultats semblent confirmer que l’utilisation d’un champ visuel étendu permet une navigation plus efficace, en diminuant le temps moyen pour effectuer une tache. Parmi les différentes projections non planes testées, une préférence pour les projections équirectangulaire et de Hammer a été exprimée. Nous avons également traité le problème de conflit d’indice de profondeurs rencontré dans les images stéréoscopiques lorsqu’un objet affiché en parallaxe négative est partiellement occulté par un bord du support d’affichage. Nous avons proposé SCVC (Stereoscopy Compatible Volume Clipping, le découpage de la scène selon le volume compatible avec la stéréoscopie) pour résoudre ce problème en n’affichant que la partie de l’espace qui n’est pas sujette au conflit d’indice de profondeur. La méthode a été évaluée et les résultats ont montrés que SCVC améliore significativement la perception de la profondeur et que les utilisateurs expriment une préférence pour cette méthode. L’extension du champ visuel humain ouvre de nouvelles perspectives pour l’exploration ou la surveillance de l’environnement d’un utilisateur. Cette extension pourrait bénéficier à diverses applications, que ce soit dans le contexte d’un environnement réel ou virtuel. Pour la sécurité des personnes ou la défense, des pompiers, des policiers ou des soldats pourraient tirer avantage d’un champ visuel étendu. Ce type de visualisation peut également profiter à l’exploration rapide d’environnements virtuels ou à la recherche d’objet dans ces derniers. / Who have never wanted to have eyes in the back of his head? This doctoral thesis proposes to study the extension of the human field-of-view (FoV) in both real and virtual environments. First we have designed FlyVIZ, a new device to increase the human FoV. It is composed of a helmet, combining a catadioptric camera, a HMD and an image processing algorithm. Wearing this device allows a user to experience 360° vision of its surroundings. The prototype is demonstrated through scenarii such as grasping an object held out behind their back without turning their head or walking backward through doorways. Then we have proposed a novel method to render virtual environments with wide FoV in real-time. To solve the rendering issue induced by usage of non-planar projections, we introduce a special stage in real-time rendering pipeline. Our method was then adapted for real-time stereoscopic rendering with 360° FoV. We have conducted a preliminary evaluation of real-time wide FoV rendering for a navigation task in virtual reality. Our results confirm that using a wide FoV rendering method could lead to more efficient navigation in terms of average task completion time. Among the different tested non-planar projection methods, the subjective preference is given to equirectangular and Hammer projections. We also address the problem of frame cancellation, generated by the conflict between two depth cues: stereo disparity and occlusion with the screen border. We have proposed the Stereoscopy Compatible Volume Clipping (SCVC), solving the problem by rendering only the part of the viewing volume free of disparity - frame occlusion conflict. The method was evaluated and results have shown that SCVC notably improved users’ depth perception and that the users expressed preference for SCVC. Wide FoV opens novel perspectives for environments exploration or monitoring. Therefore, it could benefit to several applications, both in real world context or virtual environments. In safety and security applications, firemen, policemen or soldiers could take advantage of wide FoV. Performance of searching task and fast exploration in virtual environments could also be improved with wide FoV.

yes / Purpose Perimetry is increasingly being used to measure sensitivity at central visual field locations. For many tasks, the central (0°, 0°) location is functionally the most important, however threshold estimates at this location may be affected by masking by the nearby spatial structure of the fixation target. We investigated this effect. Methods First we retrospectively analysed microperimetry (MAIA-2; CenterVue, Padova, Italy) data from 60 healthy subjects, tested on a custom grid with 1° central spacing. We compared sensitivity at (0°, 0°) to the mean sensitivity at the eight adjacent locations. We then prospectively tested 15 further healthy subjects on the same instrument using a cross-shaped test pattern with 1° spacing. Testing was carried out with and without the central fixation target, and sensitivity estimates at (0°, 0°) were compared. We also compared sensitivity at (0°, 0°) to the mean of the adjacent four locations in each condition. Three subjects undertook 10 repeated tests with the fixation target in place to assess within-subject variability of the effect. Results In the retrospective analysis, central sensitivity was median 2.8 dB lower (95% range 0.1–8.8 dB lower, p < 0.0001) than the mean of the adjacent locations. In the prospective study, central sensitivity was median 2.0 dB lower with the fixation target vs without (95% range 0.4–4.7 dB lower, p = 0.0011). With the fixation target in place central sensitivity was median 2.5 dB lower than mean sensitivity of adjacent locations (95% range 0.8–4.2 dB lower, p = 0.0007), whilst without the fixation target there was no difference (mean 0.4 dB lower, S.D. 0.9 dB, p = 0.15). These differences could not be explained by reduced fixation stability. Mean within subject standard deviation in the difference between central and adjacent locations' sensitivity was 1.84 dB for the repeated tests. Conclusions Perimetric sensitivity estimates from the central (0°, 0°) location are, on-average, reduced by 2 to 3 dB, corresponding to a 60–100% increase in stimulus luminance at threshold. This effect can be explained by masking by the nearby fixation target. The considerable within- and between-subject variability in magnitude, and the unknown effects of disease may hamper attempts to compensate threshold estimates for this effect. Clinicians should interpret central perimetric sensitivity estimates with caution, especially in patients with reduced sensitivity due to disease.

yes / There is limited information regarding the views of patients, as healthcare consumers, on visual field testing, and no information regarding their preferences for future test developments. This study aimed to increase knowledge of patients' subjective experience of visual field assessment and to explore their opinions and priorities regarding current active areas of research and development. Online questionnaire with purposive sampling design. Adults who regularly perform visual field tests in Australia who report having glaucoma or being at risk of glaucoma. An anonymous survey, implemented using the Qualtrics webtool, with both closed and open ended questions designed to explore opinions regarding visual field testing, visit attendance for perimetry, as well as priorities for developments. The survey assessed three domains: 1) opinions regarding visual field test duration and visit frequency; 2) subjective experience; and 3) perspectives on future developments for perimetry. 152 complete survey responses were obtained. The median (IQR) age of participants was 66 (60-72) years. Most participants (70%) had experience of performing more than 11 visual field tests. Participants recalled that they completed visual field tests in median of 6 minutes (IQR: 5-8 minutes) and were willing to accept additional time (median: 5, IQR: 3-6 minutes) to obtain more information. Participants were prepared to increase both the number of visual field tests per eye and the frequency of visual field tests (median: 3, IQR: 2-4 visits per year), in order to gain more information about their visual status. Regarding future developments, the most preferred option was "similar test times but an increase in the level of information about my visual field", which ranked significantly higher than all other options including "shorter test times that maintain the currently available level of information about my visual field." Our study confirms, in a different population and healthcare system, previous research reporting patient perspectives on visual field assessment. We further reveal that healthcare consumers show a strong preference for accurate information about their vision and report being prepared to undergo longer visual field tests or more visual field tests to achieve that outcome.

This dissertation research had three primary objectives. The first was to develop and evaluate a metric of image quality that incorporates a model of suprathreshold contrast and is based upon the perceived magnitude of suprathreshold contrast. The second objective was to determine the effects that common display characteristics, such as MTF shape, noise, and field of view, have on a display observer's ability to perceive egocentric motion from a display. The third and final objective was to provide a discussion of the use of image quality metrics for the evaluation of displays that are designed to facilitate motion perception. To meet these objectives, two experiments were conducted. The first experiment investigated the effects of the display Field of View, Dynamic Contrast Range, Noise Level, and Bandwidth on perceived image quality. The second study investigated the effects of these same display parameters as well as the effect of terrain type on observers’ sensitivity to changes in the speed of image motion. Existing visual psychophysical data were used to propose the two additional image quality metrics, the Perceived Contrast Magnitude (PCM) and the Weighted Perceived Contrast Magnitude (WPCM). Each of these metrics provides some additional model parameters to the Modulation Transfer Function Area (MTFA). However, based upon the studies that were conducted in this dissertation, it appears that the Integrated Contrast Sensitivity (ICS) and Square Root Integral (SQRI) provide significantly better estimates of perceived image quality than do MTFA, PCM, or WPCM. Results indicate that the display parameters of Bandwidth, Field of View, and Noise Level, plus several interactions significantly influenced the observers’ sensitivity to changes in the speed of images. One interaction indicated that observers were more sensitive to changes in the speed of images when the scene contained a lot of contextual information or when the scene was viewed through a display with reasonably high bandwidth and low noise level. However, when the bandwidth of the system was decreased, the noise level was increased, and the contextual information in the image was reduced, the observer's sensitivity to changes in motion was degraded when viewing the image through a small field of view display (20 deg) but it was not degraded when viewing the image through a larger field of view display (47 deg). Based upon the evidence collected in this dissertation, it appears that displays designed to support motion perception should have a relatively large field of view with partitions to facilitate relative motion perception. The factors of Dynamic Contrast Range and Field of View were shown to have different effects on the perception of image quality than they have on the perception of changes in the speed of an image. Therefore, the use of image quality metrics for the evaluation and design of displays that must support the veridical perception of motion should be questioned. Instead, it appears that a task specific evaluation technique should be developed for the evaluation of these displays. / Ph. D.