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X. Chai, J. Fan, S. Ling, C. Dai, Q. Ren; Positioning Performance and Size Matching of Simulated Phosphenes Based on Tactile Guidance. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4223.
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In this abstract, we investigate the dispersion and accuracy of phosphene positioning and size matching performance based on simulated vision using tactile guidance.
The system is consisted of a 5DT head-mounted display, a self-developed experimental software system and a self-designed tactile positioning mask and size evaluation board. The head mounted display (HMD) is used to display the simulate phosphenes. The tactile mask and the size evaluation board are used to position the simulated phosphenes and to judge the size of them, respectively. Twenty volunteers from 24 to 30 years old are recruited in the study. Training is performed before the actual trial in order to make the subjects familiar with the experimental procedure. The subjects are asked to point out the phosphenes on the touch screen which is covered by the tactile mask use their fingers. The distance and the vision angle both can be exactly expressed by the tactile guidance. The time between the appearance of simulated phosphene and the identified position recorded by touch was recorded by a timer. The effect of visual angle, the effect of different stimulation modes, dot size, dot contrast and the long-term effect are studied. The dispersion and accuracy of positioning are investigated. The size matching performance was measured under two different conditions. Two tasks were designed to taken into consideration of the effect of two distances (100cm and 50cm) and three phosphene distributions (Uniform, Gaussian I and Gaussian II). Subjects’ performances were different depending on different combination of conditions. In the distance of 100cm, the size matching errors of simulated phosphenes in Uniform distribution was least in three distributions. And in the distance of 50cm, there was no significant difference in three distributions.
With the increase of visual angle, the positioning accuracy and dispersion was also increased. The error in 4° to 24° visual angle was from 1.25° to 2.98°, with the error in 2° was 1.78°. The dispersion in 2° to 24° visual angle was from 0.29° to 1.08°. The performances under big, stable and high contrast conditions were better than that under small, flickering and low contrast conditions, respectively.
Using tactile guidance to position the simulated phosphenes could improve the positioning accuracy and dispersion. Long term learning could improve the positioning performance significantly. It was also proved the tactile size matching method was available in the artificial vision research.
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