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K. Cockerham, S. Aro, O. Pantchenko, S. Litster, W. Liu, J. Santiago, D. Liepmann; Development of a Biocompatible, Implantable Microstimulator for Closing Denervated Orbicularis Oculi in Rabbits. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5264.
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Facial nerve (CN-7) dysfunction from disease or trauma results in an inability to close the eyelid with subsequent corneal damage, vision loss and pain. Current treatments are palliative and insufficient, resulting in visual blurring and otherwise incomplete resolution of complications. Our goal is to develop a dynamic, bio-compatible, implantable electro-chemical microstimulator to close dysfunctional eyelids in synchrony with the contralateral functioning eyelid. We have previously achieved lid closure with an implant but signs of pain were observed. In order to reduce the amount of electrical stimulation, optimal electric wave parameters were ascertained and will be coupled with chemical drug delivery to produce robust blinks without pain.
The facial nerves of Female New Zealand white rabbits were transected. Modified EMG needles were connected to function generators and then placed around the orbicularis oculi of the denervated rabbits. High-speed videography and computerized calculations were used to calculate the percentage of closure of the palpebral fissure due to stimulation. Optimal electrode locations, electric wave pulse widths, pulse number, phase delay, amperage and frequency were found. These were repeated over a time period of several months post-denervation.
Optimal electrode placement was found to be at the medial and lateral canthi. Optimal electric wave parameters were determined for pulse width and number, phase delay, frequency, and amperage.
Coupled with chemical delivery for maintenance of denervated muscle and synergistic lowering of electrical stimulation necessary for closure, a microstimulator chip will be manufactured to utilize these optimal parameters for closing the eyelids of patients with facial nerve (CN-7) dysfunction. Future work will involve optimizing the delivery of drugs and developing a synchronizing sensor for the contralateral side.
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