Hi @maryam, If you have some skill in programming then you can access this metric using the Tobii XR SDK where we refer to the user-eye tracking distance as the gaze origin, which originates from the eye. The 3D position of the eye relative the eye tracker can then be accessed by
We describe this in more detail @ https://vr.tobii.com/sdk/develop/unity/documentation/api-reference/
Hopefully, this should point you in the right direction, please let us know how you get on. Best Wishes.