ID Number		1390
Study Type		Engineering & Physics
Model		Modeling of tissue heating due to retinal implants using 2 MHz inductive stimulus as a prosthesis for macular degeneration and eye damage
Details		Modeling of heat generated by RF stimulation circuitry in patients with retinitis pigmentosa and age-related macular degeneration. In these diseases, limited reconstruction of vision is being developed using implanted microchips to provide electrical stimulation to existing viable ganglion and bipolar cells. In these prosthetic devices, the major mechanism of power and data communication is envisioned to be a via 2 MHz inductive coupling to the implant using coils. This authors report methods and models to estimate heat induced in the human eye and surrounding head tissues by such a retinal prosthesis. A two-dimensional 0.25-mm high-resolution human head model complete with choroidal blood flow and properties of the complex implanted circuitry was developed and FDTD numerical methods were used for both electromagnetic and thermal modeling. The authors report temperature increases of approximately 0.6 and 0.4 C in the midvitreous of the human eye in the absence and presence of choroidal blood flow, respectively, with correspondent temperature rises of 0.19 and 0.004 C on the retina. Comparison with in vivo experimental measurements on intraocular heating in dog eyes shows good agreement.
Findings		Effects (only at thermal levels)
Status		Completed With Publication
Principal Investigator		North Carolina State University, USA
Funding Agency		NIH, USA
Country		UNITED STATES
References		DeMarco, SC et al. IEEE Trans. Ant. Prop., (2003) 51:2274-2285
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