Visual search and reading in patients with macular degeneration - eye movements and mathematical modelling
Final Report Abstract
Key findings: In the Berlin part of the project, we investigated visual search with central vision loss (CVL). Visual search contributes to a variety of visual everyday tasks, ranging from purposefully locating objects to supporting spatial orienting. In standardized forms, visual search is a widely used laboratory paradigm in psychology of attention. Searching with progressive CVL is thus on the one hand a challenge for patients with macular degeneration (MD), on the other hand a promising research tool for cognitive psychologists. By applying visual search tasks with graded target saliency (a) to healthy adults with different levels of simulated scotomata, and (b) to MD patients in different stages of the disease, we essentially found two reliable results: (1) Concerning application, we could resolve inconsistent findings in the literature by proposing that the optimal strategy of attention allocation depends on the stage of the CVL. When central vision was only blurred, it was most adaptive to focus attention even more narrowly than normal in order to find a target of low saliency. In contrast, when central vision was completely lost, the best strategy was to keep attention constantly wide regardless of the saliency of the target. (2) Concerning basic research in cognitive psychology, we used CVL conditions in order to investigate the relationship between retinocortical function and attentional processes. With intact central vision, these two processes are usually coupled: objects are inspected with the retinotopic region of sharpest vision, and attention is concentrated there. Since we reliably found that with CVL, it was not adaptive to concentrate attention in a retinally peripheral region where vision is relatively sharpest but instead to distribute it widely, we concluded that allocation of attention does not serve retinocortical function but operates as an independent process. In the Potsdam part of the project, we investigated fixational eye movements and microsaccades during central and peripheral fixation. Analyses were based on advanced detection procedures and statistical evaluation using surrogate time series. Our results indicate that reduced image motion immediately before upcoming microsaccades disappears under peripheral fixation. This new finding will be further investigated using experimentation and mathematical modeling. At present, applications are limited to recommending some general guidelines on how visually impaired MD patients might optimize their visual search behavior, like “If focusing attention more narrowly does not help in locating a target, try to spread your attention widely”. Follow-up research is needed in order to design and evaluate specific training programs for rehabilitation. Compared to the project proposal, the main and most disadvantageous surprise concerned the characteristics of MD patients. From the literature, it seemed to be standard to record eye movements in these patients. However, we found that these data are far from reliable. Secondly, in most MD patients the two eyes are affected to a largely different level. It is widely unknown how much input from which eye is used to form the conscious percept. Therefore the dilemma arose whether to examine visual behavior monocularly or binocularly. Whereas the second is the ecologically valid condition, only the first can be controlled and related to ophthalmological findings. Consequently, research on reading (Potsdam) was cancelled and replaced, and the three partner projects in Berlin/Potsdam and Magdeburg could not collaborate as closely as planned. Instead, we decided to conduct large parts of the research with simulated scotomata than with real patients.
Publications
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(2011). Visual search and eye movemements in patients with agerelated macular degeneration (AMD). Perception, 39 (supplement), p. 168
Wienrich, C. & Müller-Plath, G.
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(2011). Visual Search and Fixation in Patients with Age-Related Macular Degeneration (AMD). In: F. Vitu, E. Castet, & L. Goffart (Eds.). Abstracts of the 16th European Conference on Eye Movements. Journal of Eye Movement Research, 4(3), p. 27
Wienrich, C., Herbik, A., Hoffmann, M., & Müller-Plath, G.
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(2011). Visual Search and Fixation in Patients with Age-Related Macular Degeneration (AMD). In: K. Bittrich, S. Blankenberger, & J. Lukas (Eds.): Beiträge zur 53. Tagung experimentell arbeitender Psychologen, p. 192. Lengerich: Pabst
Wienrich, C., Herbik, A., Hoffmann, M., & Müller-Plath, G.
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(2013). Visual Search with central Scotoma - A simulation Study. In: U. Ansorge, E. Kirchler, C. Lamm, & H. Leder (Eds.): Abstracts of the 55th Conference of Experimental Psychologists, p. 187. Lengerich: Pabst
Wienrich, C. & Müller-Plath, G.
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(2015). Die Verteilung von Aufmerksamkeit bei zentralem Sehverlust. Technische Universität Berlin: Dissertation
Wienrich, C.
