A method for training an eye tracking model, wherein the eye tracking model is adapted to estimate eye tracking data based on sensor data from a first eye tracking sensor of a new eye tracking system, wherein the first eye tracking sensor is arranged to monitor an eye, the method comprising: receiving sensor data, wherein the sensor data is obtained by the first eye tracking sensor at a time instance; characterized by: receiving reference eye tracking data for said time instance generated by an old eye tracking system comprising a second eye tracking sensor, arranged to monitor the eye, wherein the reference eye tracking data is generated by the old eye tracking system based on sensor data obtained by the second eye tracking sensor at said time instance; and training the eye tracking model based on the sensor data obtained by the first eye tracking sensor at said time instance and the generated reference eye tracking data for said time instance, wherein training the eye tracking model comprises: estimating eye tracking data for said time instance using the eye tracking model and the sensor data obtained by the first eye tracking sensor at said time instance; applying an objective function to at least the eye tracking data estimated by the eye tracking model for said time instance and the generated reference eye tracking data for said time instance; and updating the eye tracking model. receiving sensor data, wherein the sensor data is obtained by the first eye tracking sensor at a time instance; characterized by: receiving reference eye tracking data for said time instance generated by an old eye tracking system comprising a second eye tracking sensor, arranged to monitor the eye, wherein the reference eye tracking data is generated by the old eye tracking system based on sensor data obtained by the second eye tracking sensor at said time instance; and training the eye tracking model based on the sensor data obtained by the first eye tracking sensor at said time instance and the generated reference eye tracking data for said time instance, wherein training the eye tracking model comprises: estimating eye tracking data for said time instance using the eye tracking model and the sensor data obtained by the first eye tracking sensor at said time instance; applying an objective function to at least the eye tracking data estimated by the eye tracking model for said time instance and the generated reference eye tracking data for said time instance; and updating the eye tracking model. receiving reference eye tracking data for said time instance generated by an old eye tracking system comprising a second eye tracking sensor, arranged to monitor the eye, wherein the reference eye tracking data is generated by the old eye tracking system based on sensor data obtained by the second eye tracking sensor at said time instance; and training the eye tracking model based on the sensor data obtained by the first eye tracking sensor at said time instance and the generated reference eye tracking data for said time instance, wherein training the eye tracking model comprises: estimating eye tracking data for said time instance using the eye tracking model and the sensor data obtained by the first eye tracking sensor at said time instance; applying an objective function to at least the eye tracking data estimated by the eye tracking model for said time instance and the generated reference eye tracking data for said time instance; and updating the eye tracking model. estimating eye tracking data for said time instance using the eye tracking model and the sensor data obtained by the first eye tracking sensor at said time instance; applying an objective function to at least the eye tracking data estimated by the eye tracking model for said time instance and the generated reference eye tracking data for said time instance; and updating the eye tracking model.