In a study published in PNAS we show how eye movements can be used to measure the level of attention of students in online education:
Jens Madsen , Sara U. Julio , Pawel J. Gucik, Richard Steinberg , and Lucas C. Parra, Synchronized eye movements predict test scores in online video education, Proceedings of the National Academy of Science, February 2, 2021 118 (5) e2016980118.
We can also look in to depth when students are paying attention in the video. Below we added traces on the bottom which indicate how synchronized eye movements and pupil size are between students at that point in time. When this inter-subject correlation (ISC) is above the pink-shaded area the synchronization is statistically significant.