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J. D. Dorn, A. K. Ahuja, M. Arsiero, A. Caspi, M. J. McMahon, D. Nanduri, R. J. Greenberg, Argus II Study Group; The ArgusTM II Retinal Prosthesis Provides Complex Form Vision for a Subject Blinded by Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3020.
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To test whether a subject can perceive complex shapes created by patterned multi-electrode stimulation of the Argus II retinal prosthesis. These subjects have shown varying visual abilities with their systems, as detailed in other presentations at this conference. Many of the previous experiments used to measure the subjects’ vision involve stimulation as determined by real-time video input. These experiments may involve head scanning, motor control, and many environmental variables (e.g., lighting and stimulus contrast). In this experiment, we bypassed stimulation from the camera, instead directly stimulating groups of electrodes under computer control, in order to determine whether a subject can perceive complex shapes without the benefit of head scanning.
The Argus II retinal prosthesis system includes a 10 x 6 electrode array implanted epiretinally, a tiny video camera mounted on a pair of sunglasses, and a small external computer that processes the video and determines the stimulation current of each electrode in real time. Patterns of electrodes that made up multiple complex shapes - such as parallel lines, squares, and simple letters such as "H" and "L" - were stimulated at different current amplitude levels in randomized trials (five repeats per pattern). After each stimulation, the subject was asked to draw the shape he perceived on a touch screen monitor. The subject was not trained on the specific patterns, had no prior knowledge of the shapes that would be used, and was not given feedback about his responses.
Preliminary results provide strong evidence of form vision with the Argus II retinal prosthesis. For example, one subject’s touch screen drawings closely reproduced the expected shape in most or all trial repeats (interleaved with other shapes) of several patterns, such as an "H", a triangle, a "T", and several parallel lines. To our knowledge, this is the first demonstration that a retinal prosthesis subject can perceive complex shapes with intersecting lines without head scanning when patterns of multiple electrodes are stimulated.
The Argus II retinal prosthesis provides form vision for at least one implanted subject.
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