eye tracker

US psychologist Edmund Huey built what might be the first eye tracker, using a sort of contact lens with a hole for the pupil.
The lens was connected to an aluminum pointer that moved in response to the movements of the eye.
The first non-intrusive trackers were built in the 1930s by US professor G T Buswell, using beams of light that were reflected on the eye and then recording them on film.
He conducted systematic studies in to reading and picture-viewing.