An eye-mountable device includes an enclosure material, a sensor system, and a controller. The enclosure material has a first surface and a second surface. The first surface is configured to be removeably mounted over a cornea and the second surface is configured to be compatible with eyelid motion when the concave surface is so mounted. The sensor system is disposed within the enclosure material. The sensor system has at least one value that varies with changes in a gazing direction of the cornea. The controller is disposed within the enclosure material and electrically connected to the sensor system. The controller is configured to measure the value of the sensor system to detect the changes in the gazing direction.