Browsing by Subject "Vision disorders"
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Item Spatio-temporal contrast sensitivity in Parkinson's patients and age-equivalent controls(Texas Tech University, 1995-08) Poston, Jenny NThe elderly suffer from a higher incidence of visual problems than does the rest of the population. Older individuals often report recurrent visual problems which may persist in individuals with no apparent occular pathology and with normal or near-normal acuity. However, elderly individuals are not the only populations that report ill-defined visual difficulties. Many patients with various neurologic conditions also report vague visual problems which persist in spite of normal or near-normal acuity. Research is now indicating that traditional tests of visual acuity do not adequately assess how well a person sees. An alternative to traditional vision tests is Contrast Sensitivity (CS) testing. CS is a vision test that systematically varies contrast and frequency, thus measuring the ability to see targets covering the full range of object sizes encountered in daily activities. By detecting visual deficiencies at a wide variety of spatial frequencies, CS allows a more detailed assessment of visual capacity. The present study investigated the relationship between spatial frequency and temporal modulation with respect to their impact on the contrast sensitivity of Parkinson's patients and age-equivalent controls. Individuals in various stages of the disease were assessed to evaluate how CS is affected by the progression of Parkinson's disease. Results from the study revealed distinct differences between Parkinson's patients and controls with respect to CS, as well as significant differences between the four stages of Parkinson's disease evaluated in this study. Temporal modulation and spatial frequency were found to have a significant impact on contrast sensitivity, both independently and in an interactive fashion. Specifically, these results indicated that in order to maximize CS for Parkinsonians and controls in the widest possible range of circumstances, a slow pulsing modulation is optimal. Lack of modulation was found to be extremely detrimental at very low spatial frequencies, but did not have as negative an impact at mid- and high-range spatial frequencies. These findings indicate that, whenever possible, it is important to take into consideration the range of spatial frequencies involved in a task and choose the temporal modulations that are most advantageous for the circumstances.Item Students with visual impairments' perceptions of the accessibility of the Internet(Texas Tech University, 2003-05) Siew, Lai KeunThe Internet has a tremendous potential to improve the lives and increase the independence and confidence of students with visual impairments. In the last ten years, federal and state legislation requires that information technology be accessible to people with disabilities. The provision of assistive technology (AT) is essential to the people with disabilities' full participation in advanced information technologies. Furthermore, many organizations have formulated different accessibility standards and guidelines that help authors and designers make their Internet documents accessible to the broadest possible audience, especially for people with visual impairments, because they are the user group that currently has the most difficulty interacting with Web content. However, recent studies showed that advanced information technology and communications networks are not really available, affordable or accessible to people with visual impairments. Most of the early studies focused on the accessibility of the computer and AT, but failed to take into consideration the accessibility of the Internet. Additionally, most of these studies were more interested in people with disabilities. A paucity of research is concerned with the secondary school students with visual impairments. This leaves a gap between what legislation requires and what is happening to students with visual impairments today. This study is devised to examine more closely secondary school students with visual impairments' perceptions of the accessibility of the Internet. This study investigated the following research questions: (1) To what extent are students with visual impairments using the Internet now? (2) What are the most prominent barriers that hinder students with visual impairments using the Internet? (3) What are the most prominent motivators that motivate students with visual impairments overcome the barriers using the Internet? The accessibility of the Internet has the potential to enhance the lives of students with visual impairments as well as to deny them equality of access to information. In particular, this new technology has the potential to enable or to create difficulties for students with visual impairments in the new millennium. Concerns about the Internet and the accessibility for students with visual impairments are evolving issues for the next decade.