An eye tracker consists of illuminators that illuminate near infra-red light onto your eye. This light creates a reflection also known as a glint on your cornea. Our sensor picks up that reflection and we can pick up your gaze point on a screen.
When you calibrate, we measure characteristics and calculate the personal differences such as where your pupil is located in relation to your cornea and fovea at the back of your eye. We do this to give you the best accuracy possible.
Therefore, it is not required to re-calibrate on a regular basis unless you have changed your light environment. We do however recommend you to do one calibration in a light environment and one when it's dark to have the best tracking result possible.
If you have glasses or lenses, we recommend that you create two different profiles.