Title: Eye Tracker Accuracy: Quantitative Evaluation of the Invisible Eye Center Location,
Abstract: Purpose. We present a new method to evaluate the accuracy of an eye tracker
based eye localization system. Measuring the accuracy of an eye tracker's
primary intention, the estimated point of gaze, is usually done with volunteers
and a set of fixation points used as ground truth. However, verifying the
accuracy of the location estimate of a volunteer's eye center in 3D space is
not easily possible. This is because the eye center is an intangible point
hidden by the iris. Methods. We evaluate the eye location accuracy by using an
eye phantom instead of eyes of volunteers. For this, we developed a testing
stage with a realistic artificial eye and a corresponding kinematic model,
which we trained with {\mu}CT data. This enables us to precisely evaluate the
eye location estimate of an eye tracker. Results. We show that the proposed
testing stage with the corresponding kinematic model is suitable for such a
validation. Further, we evaluate a particular eye tracker based navigation
system and show that this system is able to successfully determine the eye
center with sub-millimeter accuracy. Conclusions. We show the suitability of
the evaluated eye tracker for eye interventions, using the proposed testing
stage and the corresponding kinematic model. The results further enable
specific enhancement of the navigation system to potentially get even better
results.