For many years, eye-tracking was used as a tool in education research and by medical researchers and physicians more than anywhere else because it was so expensive. It wasn’t until later in the century that it became more accessible to a new niche: marketers.
Eye-tracking used for marketers and designers
In the 1980s, marketing groups really began using eye-tracking to measure the effectiveness of ads in magazines. Eye-tracking was able to determine what parts of a magazine page were seen, which elements of the page were actually read, and how much time was spent on each part. I found this interesting video about eye tracking in youtube:
Sadly, I don't have the machine to do my surveys. However, I was told each respondent to hold their pen or highlighter as they read the passage. I asked them not to pull their pen, remember the blind drawing? it has the same concept, except... they not do it blindly.