The aim of this proposal is to develop power and data telemetry systems for a new generation of hermetic miniaturized neural stimulators suitable for chronic implantation in a patient's eye to treat degenerative diseases of the retina. These retinal prostheses will necessarily be very small in order to be implanted onto the outside of the eye, and will therefore contain no battery. The devices will receive image data from a camera worn by the patient on a pair of glasses. Both power from an external battery and data from the external camera will be transmitted wirelessly to the prosthesis. This is done by placing an external coil near the implanted coil of the prosthesis. Delivering sinusoidal current to the external coil creates a magnetic field that induces a voltage in the implanted coil. These sinusoidal currents can be modulated to encode data. Retinal prostheses developed in the past by our group and others have implemented between 16 and 60 independent stimulating channels, or pixels. The VA Center for Innovative Visual Rehabilitation (CIVR) strives to build a retinal prosthesis with at least 256 channels for future clinical trials. Such a device will require both more transmitted power to support the large number of channels, and a higher data transmission bandwidth to supply the additional stimulation information. This proposal aims to develop this next-generation telemetry system. Additionally, since this prosthesis is meant for use in humans, our optimized telemetry system will include new safety features. It will implement bidirectional telemetry to send information to the external controller describing the function of the implant, waveforms from the stimulating electrodes, and measurements from the implant's power supplies. The first of these will be used to ensure that the implant is working properly, with no malfunctions or errors in receiving data. The second will be used to monitor the electrochemical status of the electrodes to ensure they are not changing significantly over time. The third piece of information, measurements of the implant's power supplies, will be used to adjust the power telemetry system to deliver just the right amount of power. Too little power can make the implant function improperly, and too much can cause unnecessary heat dissipation and even damage to the device. The final power and data telemetry system will be incorporated into our next-generation 256-channel retinal prosthesis, which will be enclosed in the state-of- the-art titanium package being developed by other members of the CIVR team. These prostheses will be tested by the surgical team of the CIVR in Yucatan minipig trials. After that, we plan to enter clinical trials in humans with the hop that this device will become clinically available to the blind. This 256-channel device made possibly with this optimized telemetry system is expected to open up to the VA and to blind veterans new rehabilitative possibilities through more specific, targeted neural stimulation than has previously been possible- especially for the restoration of truly useful vision to blind patients, but also in other areas of medicine such as deep brain or spinal cord stimulation. In sum, it is our hope that the blind population we serve will ultimately benefit from the improved visual acuity that will arise from our ability to create complex, highly biostable retinal neurostimulators; additionally, the channel capacity and efficacy of future wireless implantable prostheses of all types is expected to be improved.
As the veteran population ages in the years to come, the loss of the ability to perform the activities of daily living resulting from vision loss due, for example, to age-related macular degeneration (AMD) will occur with great social costs. Action must be taken soon to develop a viable visual prosthesis that can restore truly useful vision to these patients; AMD is the leading cause of blindness in the US. The proposed effort is aimed at development technologies to wirelessly send power to the implanted prosthesis from an external battery, while also sending image data to the prosthesis from an external camera. These developments will make possible a retinal prosthesis with a clinically useful number of stimulation channels, or pixels. According to the VA's own estimates, the number of veterans with significant visual impairment will reach 430,000 by the year 2011. There exists no current treatment that effectively restores lost vision in the majority of AMD patients, and the urgency of developing rehabilitative means for the growing patient population cannot be overstated.
| Krishnan, Ashwati; Kelly, Shawn K (2015) On Using Residual Voltage to Estimate Electrode Model Parameters for Damage Detection. IEEE Biomed Circuits Syst Conf 2015: |
| Kelly, Shawn K; Ellersick, William F; Krishnan, Ashwati et al. (2014) Redundant safety features in a high-channel-count retinal neurostimulator. IEEE Biomed Circuits Syst Conf 2014:216-219 |
| Krishnan, Ashwati; Kelly, Shawn K (2012) On the cause and control of residual voltage generated by electrical stimulation of neural tissue. Conf Proc IEEE Eng Med Biol Soc 2012:3899-902 |
| Shire, Douglas B; Ellersick, William; Kelly, Shawn K et al. (2012) ASIC design and data communications for the Boston retinal prosthesis. Conf Proc IEEE Eng Med Biol Soc 2012:292-5 |
