An IOP control system provides drainage from an anterior chamber of the eye to a drainage location at the eye. The system has a valve with an open flow position and a closed zero flow position. A sensor system includes a first sensor arranged to detect a first pressure representative of IOP. A controller receives data representing the detected pressure from the sensor system and compares the data to an upper pressure threshold and a lower pressure threshold to determine whether to change the state of the valve system in a bimodal fashion.
