Si-LSI Based Stimulators for Retinal Prosthesis

In this presentation, we demonstrate a pulse-frequency-modulation (PFM)-based retinal stimulator for sub-retinal implantation using standard CMOS technology with low voltage operation of 1.2 V. A PFM-based photosensor converts input light intensity to electrical pulse trains whose frequency is proportional to the input light intensity. To employ simple image processing function, 1-bit pulse domain operation is introduced and demonstrated. A packaging technology for ocular implantation is also discussed. We have proposed and demonstrated a multi-chip architecture with expandability of the number of stimulus electrodes and flexibility of bending along the eye-ball. A fabricated stimulator based on this architecture is implanted in a rabbit eye and achieved to obtain EEP (electrical evoked potential) signals.