A t age 11 Lianna Bryant finally got her voice.
Lianna — who has quadriplegic mixed-type cerebral palsy — can make sounds but she cannot speak and lack of motor control makes it impossible for her to use sign language. Her family had tried various communication tools utilizing head motion which Lianna has some control over but they were exhausting. “I’d have to wipe sweat off her head ” describes her mother Utawna Leap on the website cerebralpalsy.org.
In 2009 however Lianna’s inner thoughts and feelings became more than just a gleam in her eye. Using a specialized device made by the company Tobii Lianna was able to focus her eye movements — something she could entirely control without excessive exertion — to press buttons on a screen that would indicate what she wanted to say. With time she became proficient at using the system not only to communicate verbally but to read her schoolbooks online navigate the web write e-mails respond to the teacher in class and a host of other things that allowed her to keep up with her peers.
Helping Lianna emerge from her movement-restricted shell is just one-way eye tracking is being used today to improve people’s lives. There’s much more to this technology — it offers advanced ways to conduct research treat medical conditions change industry even enjoy video games. And it all comes down to the tiny movements that our eyes make all the time.
How Does Eye Tracking Work?
It actually sounds a little crazy. On average your eye will fixate on a spot for as short a duration as 100 to 300 milliseconds. How could these miniscule back-and-forth glances of your eye be tracked — and how can they mean anything?
Believe it or not researchers have been tracking eye movements for more than 100 years. Of course before the advent of computers and cameras they used to just watch people’s eyes and observe what they were looking at where their gaze was directed. The first devices developed were very crude holding the person’s head in place with metal rods and directing huge cameras at each eye. Now with technology advances eye tracking has become much easier more comfortable and less invasive.
“Eye tracking works through a mixture of lights and cameras — not too dissimilar to regular filming” explains Bryn Farnsworth Ph.D science editor for biometric research company iMotions. “However the light is infrared and is projected continuously onto the eyes and face while the camera records the light reflected from the eyes.”
The light is directed at the center of the eye where it reflects on the cornea the clear covering over your pupil. Those reflections are what’s used for tracking the eye’s gaze using complex equations.
It doesn’t feel like you’re staring into a bright light however. “The light is completely unnoticeable” Dr. Farnsworth continues “as the infrared spectrum isn’t visible to our eyes so the participant doesn’t feel anything at all.” Infrared light wasn’t chosen just for the user’s comfort; for best tracking it’s important to see the outline of the pupil clearly which is easier with a nonvisible light.
There’s also no painful machinery attached to your eyeballs. Many eye trackers are remote — they’re attached to or built into a computer screen which the user sits in front of. He can even move his head around to some degree because the computer is able to follow his eyes.
For some research wearable head-mounted eye trackers are more effective than remote ones. These look like space-age glasses that record eye activity from up close. They’re especially good for tracking stuff in the real world — like where a shopper’s eyes are drawn in a supermarket. Like any glasses though they can slip as you are using them which can interfere with data accuracy — although better calibration can make up for these types of movements.
In general quality of the eye-tracking data will vary depending on the instrument used. The more precise the eye tracker the more accurate and more valuable the data it collects.
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