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Shawn K. Kelly, William F. Ellersick, Attila Priplata, Douglas B. Shire, John L. Wyatt, Joseph F. Rizzo, III; Power and Data Telemetry Developments for a Retinal Implant. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5516. doi: https://doi.org/.
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This work is related to the efforts of the Boston Retinal Implant Project to develop a sub-retinal prosthesis to restore vision to the blind. Specifically, this poster presents progress on the telemetry system design for the prosthesis. Our implant receives both power and image data from external circuitry via an inductive telemetry link. We have applied optimization methods to our coils and system to improve coupling and efficiency.
We are developing an implant with more than 256 individually-addressable stimulation channels, and the power and data telemetry systems are being optimized to support this number of channels. We have employed inductance calculation tables in creating a spreadsheet to calculate inductance, resistance, capacitance, and self-resonance values for both the primary and secondary coil. We have also created a numerical magnetic field integrator in Matlab, which was used to optimize the coil sizes for improved coupling.Coils have been designed using these tools and have been wound by a professional vendor. We have measured the inductance, quality factor, and self-resonance frequency of the coils on a 30 MHz LCR meter. We have also measured coupling between the coils at a number of axial displacements and angular displacements, assuming varying positions of the primary coil and varying rotational angles of the patient’s eye.
Our primary coil, wound with Litz wire, was found to have a low-frequency inductance of 9.1 μH and a self-resonance frequency of 6.74 MHz. Our secondary coil, wound with magnet wire on a spherical form, was found to have a low-frequency inductance of 5.5 μH and a self-resonance at 24.92 MHz. At eye rotational angles up to 30°, the secondary coil collected magnetic flux of at least 65% of the normalized flux at 0 angular displacement.
Primary and secondary telemetry coils for power and data transfer to a retinal prosthesis were redesigned to optimize for coupling and efficiency. The coils were resized and rewound to generate sufficient coupling and angular displacement tolerance to power a retinal implant of 256 or more channels.
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