A successful restoration of vision should allow the blind to look, to see and to understand. The engineering of a microelectronic vision prosthesis has come a long way over the last forty years, but the understanding of how the restored form of vision would be interpreted and functionally applied to everyday living has made little progress until recent times. Prosthetic vision is not what most people think it would be; it is a visual scene composed of relatively large, isolated, spots of light so-called "phosphenes", very much like a magnified pictorial print. This thesis dissertation seeks to obtain a complete survey of the visual description of phosphenes from the human trial reports in the literature, simulate it, obtain a measure of the functional capacity of such visual perception, and explain the measured performance against design aspects of phosphene presentation, human perception, cognition and behaviour. Specifically, "visual acuity" (VA) was assessed on normally sighted subjects (N=15) administered with "simulated prosthetic vision". VA is a functional measure of vision highly correlated to many daily activities. Aggregating the results from the study with the other VA studies in prosthetic vision, it is shown that in general, the density of the phosphene field determines the affordable VA; however, design aspects relating to the phosphene field lattice (0.03 10gMAR with the hexagonal lattice as opposed to a square lattice) and image processing routines (0.15 10gMAR at optimised settings) can be further fine-tuned to improve VA performance. Significant performance improvement also arose from learning (0.13 10gMAR over ten visitations) and visual scanning adaptation (0.20 10gMAR with a circular scanning strategy). Performance improvements are likely related to various preferences and perceptual preferences of the human visual system. A rehabilitation program targeting the appropriate behavioural adaptation coupled with image processing routine optimised for image comprehension should provide a vision prosthesis recipient with the best functional experience to restored vision.
| Identifer | oai:union.ndltd.org:ADTP/272548 |
| Date | January 2009 |
| Creators | Chen, Spencer Chin-Yu, Graduate School of Biomedical Engineering, Faculty of Engineering, UNSW |
| Publisher | Publisher:University of New South Wales. Graduate School of Biomedical Engineering |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | http://unsworks.unsw.edu.au/copyright, http://unsworks.unsw.edu.au/copyright |
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