A system, a head-mounted device, a computer program, a carrier, and a method for a head-mounted device comprising an eye tracking sensor, for updating an eye tracking model in relation to an eye are disclosed. First sensor data in relation to the eye are obtained by means of the eye tracking sensor. After obtaining the first sensor data, the eye tracking sensor is moved in relation to the eye. After moving the eye tracking sensor, second sensor data in relation to the eye are obtained by means of the eye tracking sensor. The eye tracking model in relation to the eye is then updated based on the first sensor data and the second sensor data.