Use eye tracking to induce hallucinations

I heard there were new cell phones with front facing cameras specifically track eye movement so that content could be scrolled for the reader. I think similar eye tracking could be used for psych ops to intentionally put the reader in a state of mental imbalance.

For example if one knew but the readers browsing history that they were paranoid about some thing certain words or images could be imbedded with in websites they view. The images or words would remain on the page only until the camera notes the person has seen them , then they would instantly vanish the person would barely be aware they saw the words, and think their minds had played a trick on them, as frequency increases, the reader think they hallucinated the words. the words send to encourage frustrate, or frighten the person would become real self doubt and paranoia, and the person ability to do the tasks they had originally set out to do would be hindered.