A prosthetic device for optical control of target cells comprises a set of light sources, hardware for guiding light to the target cells, supporting hardware that holds members of the set of light sources with respect to each other and the target cells, control circuitry for controlling the set of light sources, and power circuitry that provides power to the set of light sources and the control circuitry. The device may be wearable or implantable, and may be remotely powered or employ wireless communication. The supporting hardware may comprise implantable hypodermics or cannulas, or a plate or scaffold. The set of light sources may be assembled into an array.