An implant apparatus comprising a plurality of photo sensors, a plurality of micro electrodes and circuitry coupled to the photo sensors and the micro electrodes are described. The photo sensors may receive incoming light. The circuit may drive the micro electrodes to stimulate neuron cells for enabling perception of a vision of the light captured by the photo sensors. The apparatus may be implemented in a flexible material to conform to a shape of a human eyeball to allow the micro electrodes aligned with the neuron cells for the stimulation. In another embodiment, fabrication methods for a flexible device having an array of pixel units for retina prosthesis are described. The fabrication method may comprise forming layered structures including the array of pixel units over a substrate, each pixel unit comprising a processing circuitry, a micro electrode and a photo sensor. In another embodiment, methods and apparatuses for configuring an implantable device to interface with retina cells are described. The device may comprise an array of pixel units capable of stimulating the retina cells. The pixel units may operate in a mode of operation selected from a plurality of modes including a normal mode and a calibration mode.