An eye tracker includes at least one illuminator for illuminating an eye, at least two cameras for imaging the eye and a controller. The configuration of the reference illuminator and cameras is such that, at least one camera is coaxial with a reference illuminator and at least one camera is non-coaxial with a reference illuminator. The controller selects one of the cameras to be active to increase an image quality metric and avoid obscuring objects. The eye tracker is operable in a dual-camera mode to improve accuracy.