Implants provide a means to electronically stimulate biological systems. Such stimulation may be designed to be driven by current or voltage. Although the methods are theoretically equivalent, the selection of which to employ has implications as to hardware design, stimulation strategies, and other practical impacts. We model the impact of voltage-driven stimulation, utilising models for producing current-driven approximations to voltage-driven waveforms and a current-driven model of perceived brightness of phosphenes. We give predictions as to phosphene brightness, and consider some practical impacts of choosing current or voltage driven stimulation.