@user-c09cdd I have moved the discussion here. With cognitive load, we are leaving my area of expertise. Actually, in the past I have measured cognitive load using physiological signals (e.g. EDA). It was easier to implement and get reasonable results in my research areas. With eye tracking, the literature tends towards pupil dilation. Although eye movements themselves can reveal information about cognitive processes. What sort of tasks will your participants perform?

Well I will say that stress is not cognitive load, and in fact, stress can confound measurements of cognitive load. So if you are solely using gaze data, you will have to think carefully about what it is you want to measure.