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J. Zhou, S.-I. Park, E.-T. Kim, J.-M. Seo, C. Hum, S.-J. Kim; The Electrical Retinal Stimulation System for Long-Term Animal Experiments. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2557.
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An implantable retinal prosthesis system is introduced for a chronic electrical stimulation test in an animal model. This system can provide the animal’s free movement and also protect the stimulation system from the animal’s claws and teeth during the stimulation test. In vivo experiments on rabbits are done to prove the implantation feasibility of this newly suggested stimulation system and to measure the electrically evoked potentials.
The electrical retinal stimulation system for long-term animal study consists of an external unit which provides preset stimulation patterns and an implantable stimulator which provides continuous electrical stimulation. A paired RF coil links these two units when data and power transmission are needed. The external unit has a stimulation waveform parameter selector to control the channel selection, amplitude, duration and rate of stimulation. The implantable stimulator which implemented with four IC chips (data/power receiver chip, current stimulation chip, parameter memory chip and battery charging chip) has two function modes: a stimulation mode and a battery recharging mode. To remove the external part from the animal during electrical stimulation, a small rechargeable battery and a parameter memory were introduced into the stimulator. Except for data/power receiver chip, the other chips in the internal stimulator are powered by this battery. Therefore, once the parameters are passed to the parameter memory, the external unit is no longer need. The battery could be simply recharged using an RF inductive link during battery recharging mode. Rabbits were used for testing of the retinal electrical stimulation system. Electrically evoked potentials were measured from the animals.
The electrical retinal stimulation system operates as designed. The implantable stimulator can deliver charge-balanced, biphasic currents to all stimulation channels. The current amplitude can be selected from 8 µA to 2 mA with 8uA resolution. The implanted stimulator consumed around 2 mW when delivering 216 uA biphasic current pulses of 460 us pulse width at a stimulation rate 10 Hz. Electrically evoked potentials recorded from rabbits following stimulation delivered according to various parameters will be reported.
The electrical retinal stimulation system provides a useful tool for long-term animal experiments on retinal prostheses.
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