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Mark S. Humayun, L da Cruz, Gislin Dagnelie, Jose A. Sahel, Paulo E. Stanga, Eugene Filley, Dean Eliott, Jacque L. Duncan, Robert J. Greenberg; Interim Performance Results from the Second Sight® ArgusTM II Retinal Prosthesis Study. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2594.
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To provide an update on performance outcomes in the Argus II Retinal Prosthesis Study.
Subjects had bare light perception or worse vision due to retinitis pigmentosa. All subjects were implanted with a Second Sight Argus II implant (clinicaltrials.gov NCT00407602). Visual function was evaluated by a grating visual acuity test as well as by assessing the ability to determine the direction of motion of a line and the location of a square on an LCD screen. Orientation and mobility (O&M) tests were also given, which involved following a line and finding a door.
As of December 1, 2010, 30 subjects have been implanted at 10 centers (in the main study). Subjects have been implanted an average of 28 ± 10 months (range of 16 - 42), and all have used or are using the System at home. As of 1 December 2010, the rate of adverse events, which was moderate to begin with, has been further decreased by approximately 3x in the second half of the subjects (i.e., last 15 subjects). As for implant stability, 28 out of 30 devices are intact and functioning - one device was explanted around 14 months post-implant; a second remains implanted but functions intermittently due to partial loss of the RF link that provides power and data to the array. Results on visual function tests with high-contract stimuli showed a hierarchy of function, progressing from the ability to locate an object, through the ability to detect the direction of motion, and finally to the ability to distinguish the orientation of black and white gratings. To date, the best grating visual acuity measurement was 1.8 logMAR (20/1260). Functional vision O&M tests demonstrate that subjects are significantly better at performing visual tasks with the System ON vs. OFF & that this effect is maintained during long-term follow-up (i.e. >2years).
With over 69 cumulative patient-years of follow-up on 30 subjects, this is the largest study of a visual prosthesis to date. The results confirm previous reports on the ability of the Argus II prosthesis to provide visual function and functional vision over the long-term. Higher resolution devices are in development.
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