Perceptual thresholds and electrode impedance in three retinal prosthesis subjects

Three test subjects blind from retinitis pigmentosa were implanted with retinal prostheses as part of a FDA-approved clinical trial. The implant consisted of an extraocular unit that contained electronics for wireless data, power, and generation of stimulus current, and an intraocular unit that cons...

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Bibliographic Details
Published in:IEEE transactions on neural systems and rehabilitation engineering 2005-06, Vol.13 (2), p.201-206
Main Authors: Mahadevappa, M., Weiland, J.D., Yanai, D., Fine, I., Greenberg, R.J., Humayun, M.S.
Format: Article
Language:English
Subjects:
Blindness - etiology
Blindness - physiopathology
Blindness - rehabilitation
Clinical trials
Control systems
Differential Threshold
Electric Impedance
Electric Stimulation Therapy - instrumentation
Electric Stimulation Therapy - methods
Electrical stimulation
Electrodes
Electrodes, Implanted
Equipment Failure Analysis
Impedance
implantable medical device
Implants
low vision
Microelectrodes
neural prosthesis
Optical arrays
Pigmentation
Prosthesis Design
Prosthetics
Retina
Retinal Ganglion Cells
retinal prosthesis
Retinitis Pigmentosa - complications
Retinitis Pigmentosa - physiopathology
Retinitis Pigmentosa - rehabilitation
Testing
Visual Perception
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Summary:Three test subjects blind from retinitis pigmentosa were implanted with retinal prostheses as part of a FDA-approved clinical trial. The implant consisted of an extraocular unit that contained electronics for wireless data, power, and generation of stimulus current, and an intraocular unit that consisted of 16 platinum stimulating electrodes arranged in a 4 /spl times/ 4 pattern within a silicone rubber substrate. The array was held to the retina by a small tack. The stimulator was connected to the array by a multiwire cable and was controlled by a computer based external system that allowed precise control over each electrode. Perception thresholds and electrode impedance were obtained on each electrode from the subjects over several months of testing. The electrode distance from the retina was determined from optical coherence tomography imaging of the array and retina. Across all subjects, average thresholds ranged from 24-702 /spl mu/A (1-ms pulse). The data show that proximity to the retina played a role in determining the threshold and impedance, but only for electrodes that were greater than 0.5 mm from the retina.
ISSN:1534-4320
1558-0210
DOI:10.1109/TNSRE.2005.848687