Age-related Macular Degeneration (AMD) is a retinal disease causing the progressive loss of macular vision. Initially, central vision seems like a light haze (blurred vision), which gradually becomes more and more dense. Later on, the central scotoma is entirely evolved (central vision loss), confining the patient to rely solely on peripheral vision to achieve visual tasks. The main aim of the present thesis is to investigate visual attention in adaptation to central vision loss progress. The topic might be examined from two points of view: From an applied point of view, one could ask: How does a central vision loss impact visual attention? In order to investigate this impact, different experimental paradigms might be performed with AMD patients and corresponding controls. From a more scientific point of view, one could ask: What could we learn about the interrelationship between visual acuity and visual attentional in the presence of a central vision loss? Whereas the approach in the first case reveals a descriptive character, the second case implies a theory-driven approach. At the last-mentioned approach, the central vision loss initially serves as research method, before it becomes the subject of research. This thesis focuses on the second approach. It's been systematically examined how factors of the disease itself (scotom opacity) as well as more objective parameters of the task (stimulus contrast, item size) determine the visual search. In order to model the interrelationship between the attentional focus size and visual acuity, two hypotheses were contrasted (Gradientenhypothese versus Fixationsorthypothese). In the first part of the present thesis, the following research questions were answered: How do retinal acuity and the visual attention interrelate? Does the attentional focus size depend upon the fixation point on the retina? In order to answer these two questions, the central vision loss serves as research method in the form of gaze contingent simulated scotomata. The main result of Experiment 1 revealed constant large attentional focus sizes in participants with opaque simulated scotomata. Experiment 2 underlined the results of Experiment 1, even though, no eye movements were possible. Oculomotor irritation could be excluded. The second part answered the following questions: How do AMD patients allocate their visual attention? Does this allocation depend on the progress of their central vision loss (impact of scotom opacity)? At this point, the central vision loss becomes the subject of research. In Experiment 3 and 4, the visual search behavior of AMD patients with central scotomata corresponded with simulations investigated in Experiment 1 and 2. While individual patients differed from the expectations, the results were in line with the Gradientenhypothese.
|School:||Technische Universitaet Berlin (Germany)|
|Source:||DAI-C 81/1(E), Dissertation Abstracts International|
|Subjects:||Biomedical engineering, Neurosciences, Ophthalmology|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be