Perceiving visual properties of indoor layouts with impaired vision

University of Minnesota Ph.D. dissertation. Ph.D dissertation. September 2013. Major: Psychology. Advisor: Gordon E. Legge. 1 computer file (PDF); ix, 110 pages.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