Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2003. / Vita. Includes bibliographical references (leaves 182-208).

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Purpose: An important challenge for eye care practitioners is meeting the needs of an ever-increasing elderly population. Standard vision tests are inadequate for determining performance in real life situations. One test that was developed to address this issue is the Attended Field of View (AFOV) test (Coeckelbergh et al, 2004). This test was designed to assess the functional field of view when people are allowed to make habitual head and eye movements. The original AFOV test is no longer available. This research seeks to develop a replacement AFOV test and to demonstrate its reliability as an assessment tool. Methods: Two groups of participants were recruited. The first group consisted of seven participants between the ages of 15-41 years. The second group consisted of seven participants between the ages of 59–79 years. All subjects had visual acuities equal or better than 20/25 and no history of visual field loss. A computer-generated display was observed from a 60cm distance. The display consisted of 24 white circles on a gray background and one open circle (target). The circles were organized with one circle in the centre and eight located radially at three eccentricities (4, 8, and 12 degrees). Participants were required to locate the target circle and identify the gap direction. A response was considered correct when both the location and gap direction were accurate. Using a weighted staircase method based on presentation time each location was evaluated independently. Viewing efficiency [log (1/threshold presentation time)] was obtained for each location. The data was analyzed using repeated measures ANOVA. Results: A comparison of viewing efficiency for the two age groups demonstrates that viewing efficiency is consistently lower for the older group at all three visits. The main effect of age was observed (F1,12=25.842;p=0.000). In the older group, a significant difference was found between the second and third visits. This difference was not found in the younger group. A main effect of eccentricity was found in both groups (F2,36=30.84;p<0.000), but no interaction was observed between eccentricity and group (F2,36=0.42;p=0.662). Viewing efficiency values in the older group were lower in all directions (main effect of age) (F1,96=150.36;p<0.000). Directional variations in viewing efficiency were observed showing higher values in the horizontal axes (directions Right and Left) than along the vertical axes (directions Up and Down) in both groups. A comparison of superior and inferior hemifield data shows consistent differences for both age groups. The superior hemifield (average of directions located superiorly to the horizontal axis) demonstrate higher viewing efficiency values (better performance) than the inferior hemifield. Conclusions: The use of the new AFOV test requires a practice time before its use in order to avoid the confound of a learning effect, but subsequent data is reliable in young people. The learning effect was more significant in older people and for this reason the use of the test should be preceded by a longer practice session in this population. When interpreting the results of this test one must account for eccentricity, direction, and age.

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Purpose: The prevalence of age-related visual impairment is projected to increase as the Canadian population ages. As a result, the demand for low vision service is also projected to increase. However, there is a lack of healthcare planning regarding vision rehabilitation in Canada. The current study is the first study that describes optometric low vision services across Canada. The primary purposes of this study were to determine the provision of low vision services by optometrists in Canada, the barriers to providing low vision services and the pattern and perception of referrals to specialised low vision services. The secondary purposes of this study were to examine regional differences in low vision practice and referral patterns, and to identify predictive factors associated with the extent of optometric low vision care. Methods: Practising optometrists across Canada (n=1839 or 40.5% of the Canadian optometric population) were randomly sampled so as to obtain approximately equal responses from the Western Provinces, Ontario, Quebec and the Eastern provinces. Between October 2010 to January 2011, optometrists were invited to participate in a 30-item questionnaire that included questions on personal profile, primary practice profile, types of patients seen, levels of low vision services offered, patterns of referral and barriers to provision of low vision care. Descriptive statistics were used to describe the current landscape of optometric low vision care. Chi-square analyses were used to identify any regional differences in pattern of low vision provision and/or referrals. Multivariate logistic regression was used to determine the predictive factors associated with the extent of optometric low vision care. Written comments on low vision education and provision of low vision services were first coded to represent relevant categories of information emerging from the written data. Then the patterns of coding were grouped into common themes. Results: A total of 459 optometrists responded (24.8%). Optometrists estimated that 1% (range 0-100%) of their patients were patients with low vision, yet also estimated that 10% of their patients had a best corrected visual acuity of ???6/12. Almost three-quarters of respondents would manage a hypothetical patient with minimal visual disabilities and simple visual goals with high-powered additions and lighting; however, the proportion of those who would manage with the same patient with magnifiers and filter lenses dropped to 43%. The most frequently cited barriers to providing more extensive low vision services were found to be related to financial non-viability, lack of affordability by the patient and the time-consuming nature of conducting a low vision assessment. The percentage of respondents who cited no interest in low vision was 33.5%. Many respondents would like to see more continuing education on low vision, preferably through a hands-on approach. The most frequent site of referral was CNIB (81.9%), although most of the respondents (57.1%) rarely (0-5% of the time) or almost never (0-25% of the time) received a written report from the low vision service providers. Chi-square analyses revealed that optometrists in Quebec tended to refer eligible patients to government-sponsored vision rehabilitation centres, while optometrists in Eastern provinces tended to manage patients on their own. The predictive factors associated with the extent of optometric low vision care were advanced years of practice (16+ years), having local low vision optometrists/ophthalmologists within one-day???s travel, working in a practice within a population of less than 50,000 and working in a non-solo practice. Conclusions: This study documents that optometrists may be undertaking more low vision (LV) in patients with relatively good vision than they tend to label as LV. Vision rehabilitation is of interest to a large portion of optometrists across Canada. To translate the interest into practice, barriers identified by the current study must be addressed.

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Vision provides relevant information for safe locomotion in a variety of environments. During stair locomotion visual information may be important to detect step boundaries, transitions between ground level and stairs, handrail location, and potential hazards. Although there is a large body of literature on the role of vision during locomotion there is relatively little focused on how visual information is used during stair walking. Stairs are related to a significant number of accidents in daily living, and many of these accidents are attributed to visual factors. Therefore, understanding the role of vision during stair walking could provide insight into the mechanisms involved in stair accidents. The purpose of this thesis was to investigate the properties of the visual input used to guide locomotion on stairs. Study 1 was design to describe the gaze patterns during stair locomotion with a specific focus on transitions and handrails. Study 2 investigated the effects of performing concurrent visual and non-visual tasks on walking performance and associated gaze behaviour during stair ascent. Study 3 explored the role of peripheral visual information during visual and non-visual dual tasking. Finally, Study 4 investigated the effects of restricting the lower peripheral visual field to walk on stairs. Studies relied on the measurement in health young adults of: gaze behaviour using an eye tracker, temporal characteristics of walking using foot switches, and reaction time and errors of dual task performance. Overall, the findings of these studies highlight the importance of the lower visual field in guiding stair locomotion and the specific importance for stair transitions. Moreover, foveal vision is not specifically critical to detecting handrails or steps. Results are interpreted in the light of the specialization of the dorsal ventral stream in processing peripheral visual field information. Findings of this thesis provide basic understanding on the role of vision for stair navigation with potential applications in stair-related accident prevention programs and stair design.

The combination of low-cost imaging chips and high-performance, multicore, embedded processors heralds a new era in portable vision systems. Early vision algorithms have the potential for highly data-parallel, integer execution. However, an implementation must operate within the constraints of embedded systems including low clock rate, low-power operation and with limited memory. This dissertation explores new approaches to adapt novel pixel-based vision algorithms for tomorrow's multicore embedded processors. It presents : - An adaptive, multimodal background modeling technique called Multimodal Mean that achieves high accuracy and frame rate performance with limited memory and a slow-clock, energy-efficient, integer processing core. - A new workload partitioning technique to optimize the execution of early vision algorithms on multi-core systems. - A novel data transfer technique called cat-tail dma that provides globally-ordered, non-blocking data transfers on a multicore system. By using efficient data representations, Multimodal Mean provides comparable accuracy to the widely used Mixture of Gaussians (MoG) multimodal method. However, it achieves a 6.2x improvement in performance while using 18% less storage than MoG while executing on a representative embedded platform. When this algorithm is adapted to a multicore execution environment, the new workload partitioning technique demonstrates an improvement in execution times of 25% with only a 125 ms system reaction time. It also reduced the overall number of data transfers by 50%. Finally, the cat-tail buffering technique reduces the data-transfer latency between execution cores and main memory by 32.8% over the baseline technique when executing Multimodal Mean. This technique concurrently performs data transfers with code execution on individual cores, while maintaining global ordering through low-overhead scheduling to prevent collisions.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1976. / Bibliography: leaves 113-121. / Microfiche. / vii, 121 leaves ill. 29 cm

Thesis (M.Eng.). / Title from title page of PDF (viewed 2008/01/30). Written for the Dept. of Biomedical Engineering. Includes bibliographical references.