An IOP control device for implantation in an eye of a patient is disclosed, including a housing with an entrance port and an exit port, a membrane anchored within the housing in a manner forming a flow control chamber on a first side of the membrane and a fluid flow passageway on a second opposing side of the membrane, and a position sensor system. The flow control chamber is arranged to contain a gas creating a flow control chamber pressure, and the membrane is configured to affect flow through the fluid flow passageway from the entrance port to the exit port by deflecting in response to changes in the flow control chamber pressure. The position sensor system includes a first conductive portion and a second conductive portion positioned to selectively contact the first conductive portion to indicate the position of the membrane relative to the fluid flow passageway.
