Do I need to fine tune my eye tracker for every person using it?

To make sure you have the best possible experience with your eye tracker, you should fine tune for every person using it.

All humans have different characteristics – so do our eyes. When you fine tune your eye tracker, it measures characteristics of your eyes and uses them together with an internal, anatomical 3D eye model to calculate the gaze data. This model includes information about shapes, light refraction and reflection properties of the different parts of the eyes (e.g.  cornea, placement of the fovea, etc.). During the process, several images of the eyes are collected and analyzed. The resulting information is integrated in the eye model and the gaze point for each image sample is calculated.

Tobii's eye trackers use pretty complex technology - because your eyes are unique, just like you!