Hi @erko94, could you kindly confirm the eye tracker model you are using please? As you may be aware, the Tobii Eye Control software provides fixation algorithms internally with fixation data exposed in the SDK as the start and end time and fixation position.
Certainly, there is a great deal of literature relating to the detection of fixations in general, with one such technique known as IV-T Filter. http://acuity-ets.com/downloads/Tobii%20I-VT%20Fixation%20Filter.pdf
If you could please clarify the software and hardware you are using, that would be helpful to provide a more complete answer for you.