how does eye tracking work?

If you’ve worked on your resume or website recently, you may have come across some design suggestions based on where people’s eyes tend to move. If you’re like me, you’re wondering how on earth anyone knows that people view your website like so:


Personally, I imagined something like this, except tiny and all over your eyeballs:


I knew that couldn’t be right. Rather than making a series of increasingly horrible guesses, I decided to take to the internet. It turns out there are three major types of eye tracking methodologies. 

1. Optical Tracking

For a technique used in something called “Eye Tracking”, I find this to be a rather unhelpful name, so I’m calling it “the dog photo technique”. You know how if you have your flash turned on when you take a picture of an animal, you get a crazy glowing eye effect? This technique does basically the same thing except to humans, and captures video instead of still photos. Researchers perform what would be many high schoolers’ least favorite math homework, measuring the distances traveled by the pupils and reverse-engineering them to determine what the subject was looking at.

2. Electric Potential Measurement

This technique is like an EKG for your eyes. Researchers attach a bunch of electrodes to the skin around a subject’s eye, making them look like some sort of uncoordinated bionic pirate, and capture the electrical signals produced by the eye muscles during eye movement. Although this technique is less effective than the dog photo technique at determining gaze direction, it is infinitely funnier to review at the company holiday party.

“Yarrrr, four tries and I still missed me eye!” Photo courtesy of

3. Eye-Attached Tracking

This is the technique where some readers may start squirming. It’s pretty much what it sounds like, and is the closest to my original awful guess of any of the three types of techniques. Subjects wear a special type of contact lens that can sense its own movement and transmit that movement back to the researchers to be translated into gaze locations.

So, now we know how the data is collected - the other half of the battle is considering what could be useful or likely future applications of this technology. It’s currently being used by a variety of fields in academic and scientific research, as well as marketing and website design (as seen at the beginning of this post). However, those applications have involved using eye tracking for a specific data-gathering period and then analyzing the data after the fact.

I personally wonder whether we will see this technology incorporated in real-time. Eye tracking has already been used to analyze automobile driver behavior, and many auto insurance companies are initiating “safe driving rewards” trackers that measure things like how hard you brake. What if we combined the two? Excessive downward-gazing could be an indicator of mobile phone usage or other distractions.

If you could apply eye tracking to your field, job or everyday life, what would you use it for?