Human Centered Science and Biomedical Engineering Graduate Major
Depatrment of Mechanical Engineering
Graduate School of Engineering
Tokyo Institute of Technology

Yagi Laboratory

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Visual Prosthesis

(Retinal Implant & Biohybrid Retinal Implant)


A visual prosthesis is an artificial organ to restore the sight of blind patients with electrical stimulation to the visual nervous system. Dr. Yagi has been conducting two types of the visual prosthesis; a biohybird implant and a retinal implant.

In academia, Dr. Yagi's group has been conducting basic research and system design/integration on a biohybird retinal implant, which consists of cultured neurons on MEMS (Microelectromechanical Systems). Axons of the neurons will be guided with an axon-guiding material such as a peripheral nerve graft, or a tube, which is filled with the Schwann cells and the extra cellular matrix. Therefore, the transplanted neurons will be used as living electric wires in order to connect the MEMS and the central nervous system. Since the hybrid retinal implant requires neither the retinal ganglion cells nor the optic nerve, it will be more applicable to blind diseases where the retinal ganglion cells and/or the optic nerve are NOT intact.

Biohybird retinal implant

Biohybird retinal implant project includes; development of various micro-electrode arrays with MEMS technology including a conductive polymer microelectrode array, in vitro nerve cell culture and axon guidance experiments on the fabricated microelectrode array, in vivo electrical stimulation experiments, and various computer simulations including psycho-physical evaluation of reading ability with the visual prosthesis simulator.

In industry, Dr.Yagi has directed his R&D team in industry under the support of a Japanese national research project of a visual prosthesis. His visual prosthesis consists of an extra-ocular and an intra-ocular device, and contains various technologies such as image capture and processing, wireless data&power transmission, data&power recovery and pulse generation on a full-custom IC, and electronics packaging of the fabricated IC and a stimulation electrode array. According to the visual information captured by a video camera in the extra-ocular device, the information is coded, then sent to the intra-ocular device through an infrared (IR) communication unit. After the intra-ocular device receives the IR data, it generates adequate electric pulses for stimulating the retina. The first prototype of the retinal implant was completed 2004 spring, and will be evaluated in animal and clinical tests near future.

Retinal Implant
Optic Nerve Implant
Cortical Implant

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