Browsing by Subject "Low vision"

Now showing 1 - 3 of 3
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    Beyond eye charts, the daily challenges for people with impaired vision
    (2023-05) Wu, Yueh-Hsun
    Visual impairment, which affected an estimated 596.5 million people globally in 2020, can lead to numerous challenges in daily life. However, those challenges can’t always be captured by standard clinical vision tests, such as visual acuity tests, contrast sensitivity tests, or visual field tests. This dissertation focuses on understanding real-life challenges encountered by people with visual impairment. Chapter 1 provides an overview of the dissertation. Chapter 2 examines the relationship between visual acuity measurements and people’s daily viewing experience. The results demonstrate that visual acuity, as measured on letter charts, can be estimated by people’s responses to a set of Yes/No questions asking what they can or cannot see in real-life viewing scenarios. Chapter 3 describes an online survey focusing on the reading behavior of individuals with low vision in the digital era. The results show that reading with vision was still the primary way to read, although audio or tactile methods can be used to access digital materials. Digital reading was also found to be used more than hardcopy reading. Chapter 4 reports on a longitudinal study that examined the impact of the first year of the pandemic on social isolation in older people with vision or hearing loss. The findings demonstrated that older people with visual impairment were more likely to experience social isolation and loneliness during the early pandemic in 2020. The studies presented in the thesis provide three perspectives on understanding the daily challenges encountered by people with visual impairment. These findings can be directly applied to better rehabilitation programs for improving the quality of life in people with visual impairment.
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    Does Motion Parallax Enhance the Accuracy of Object Depth Perception?
    (2022-09) Liu, Siyun
    Depth perception is essential for safe and effective mobility. When an observer moves through an environment, the retinal images of surrounding objects shift in the field of view, creating motion parallax, which can be used to infer the depths of the objects. When an observer walks forward to approach an object, the image of the object expands in the field of view, inducing expansive motion parallax; when the motion direction of the observer contains a lateral component, the object image shifts laterally to the left or right, which is termed lateral motion parallax. This thesis investigates three questions regarding the effect of motion parallax on depth perception for people with intact and artificially reduced acuity: whether motion parallax increases depth perception accuracy compared to static viewing with pictorial depth cues present; whether expansive and lateral motion parallax differs from each other in assisting depth perception; and whether continuous motion provides more benefit to accurate depth perception than object image displacement. To control the level of acuity loss, the participants included in this thesis were normally sighted, and the acuity reduction was simulated with digital filters or blur goggles. Chapter 1 provides an overview of the three experiments described in the thesis. In all three experiments, the participants looked at two objects in a virtual or physical scene and estimated the depth separation between the objects either by moving a slider on the screen or by verbal report. Chapters 2 and 3 focus on the effect of visual signals from motion parallax. The results show that when estimating object depth in a virtual scene on a computer screen, for participants with both intact acuity and artificially reduced acuity, the accuracy in the static viewing condition was low, lateral motion parallax yielded higher accuracy than expansive motion parallax, and the continuous motion was more beneficial than discrete object image displacement. Chapter 4 examines the effect of motion parallax for observers who walked in a physical space. The accuracy of depth estimation for static viewing in the physical space was higher than that in the virtual space, and the effect of observer motion was weaker. Lateral motion parallax only increased the accuracy of depth estimation when the acuity reduction was severe and the pictorial cues in the scene were manipulated to be misleading. While motion parallax is an important source of depth information in a scene presented on a screen, in the physical world, pictorial cues may often be sufficient for estimating the depth of objects, reducing the importance of motion parallax. Further investigations are needed to evaluate the importance of motion parallax for people with impaired vision.
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    Perceiving visual properties of indoor layouts with impaired vision
    (2013-09) Bochsler, Tiana Maire
    Low vision is any visual impairment that affects everyday function and is not correctable with lenses (glasses or contacts). It results in a loss of details required for object recognition and space perception, which can lead to getting lost or disoriented, even in familiar environments. Visual accessibility is the use of vision to travel efficiently and safely through an environment, to perceive the spatial layout of key features, and to keep track of one's location. To construct a public space that facilitates visual accessibility, it is necessary to predict how well people with low vision can navigate within such spaces. Two topics are the focus of this thesis: i. the recognition of steps/ramps under different environmental conditions by subjects with low vision and those with normal vision wearing acuity-reducing goggles, and ii. spatial updating in real indoor spaces with limited visual and auditory input. The ability to recognize and safely utilize steps/ramps is an important component of visual accessibility. An overview of the thesis is provided in Chapter 1. Chapters 2, 3, and 4 discuss three related research projects. Chapter 2 investigates two possible ways of enhancing step/ramp recognition for people with low vision: locomotion (walking) and visual floor texture. Normal vision subjects with artificially reduced acuity were evaluated on recognition accuracy. Locomotion enhanced performance, while floor texture detracted from it. Chapter 3 explores the recognition of steps/ramps by people with heterogeneous forms of impaired vision. The effects of distance, target type, and locomotion were qualitatively similar for low vision and normal vision with artificial acuity reduction. Recognition performance was significantly better at shorter distances and after locomotion. Chapter 4 evaluates the spatial updating abilities of normally sighted subjects wearing acuity- and field-reducing goggles. Spatial updating is the ability to keep track of one's position and orientation in an environment. We measured the accuracy of distance and direction estimates, and learned that vision status influenced estimates of distance, but not estimates of direction. Together, these studies provide insight into the visual accessibility of spaces for people with low vision, and suggest directions for future research.