Responses of retinal ganglion cells to electrical stimulation with a subretinal photovoltaic prosthesis

Abstract

Purpose: In photovoltaic subretinal prosthesis, the electrical current for reliably stimulating retinal ganglion cells (RGCs) is demanding. This study was aimed to evaluate the efficacy of enhanced current output with a divisional power supply scheme (DPSS) circuit, which provides power alternately to a subset of electrodes at a time with all the electricity.

Methods: The photovoltaic prosthesis was fabricated by the Taiwan Semiconductor Cooperation (TSMC). The prosthetic chip is equipped with a centrally located 8x8 CMOS sensors array, fabricated with 65 nm line width technology of TSMC. An independent output electrode is accompanied by individual sensor and corresponding return electrode. The chip is powered by on-chip integrated solar cells in the periphery. The chip was investigated systematically in vitro to verify the electrophysiological response of RGCs from isolated rabbit and mouse retinas using a multi-electrode array (MEA).

Results: With this chip, RGCs were successfully activated by electrical stimulation of the retinal neural network. In both rabbit and mouse retinas, the evoked spiking responses of RGCs were successfully recorded by MEA. The spike latency of these electrically evoked responses was consistent with previous studies. Furthermore, the effects of stimulation strength and frequency on RGC responses were also characterized.

Conclusions: Reliable activation of RGCs by electrical stimulation in vitro using a subretinal photovoltaic prosthesis with DPSS design demonstrates the potential and could be developed into a power-free device able to restore vision in the future.