Towards a monolithic integrated stimulator with integrated image sensor for a wide angle retina implant

Objective: To present a monolithic integrated current controlled stimulator (CCS) with a build-in image sensor for a novel independent epiretinal prosthesis with a wide angle field of view (FOV). Materials & Methods: Existing subretinal implants are limited in size by different medical boundary conditions, like the increasing risk of retina detachment. To create a novel wide angle FOV retinal prosthesis, a large carrier foil with several independent microchips is placed as an epiretinal implant and is capable of stimulating a large area of the retina through its backside electrodes. The high flexibility of the foil makes the implant bendable, which allows the implant to fit its shape to the spherical retina. Also the implant is designed to be foldable, which makes it implantable through the cornea. For this kind of implant a new application specific integrated circuit (ASIC) had to be designed for the stimulation of the retina. The ASIC contains an image sensor and controls the electrodes underneath it. Therefore the ASIC detects the local brightness on each pixel to generate the stimulation waveforms for the electrodes which corresponds to the illuminated area. The CCS signal is a biphasic constant current pulse and can be parametrized for different stimulation intensities. Discussion: The ASIC works independent since image sensor and signal processing chain are fully integrated. Thus the system is completely capsuled and only needs an external wireless power supply. The use of multiple ASICs on one single carrier foil allows stimulating a large retinal area. Because the camera is included in the eye, the projected image correlates to eye movements. Acknowledgment: This research is sponsored by the German Research Foundation (DFG) under contract No. GR3328/10-1.