What is Eye Tracking?

What is eye tracking?

What is eye tracking?

The basics

Eye tracking basics

Eye tracking, or gaze interaction, is a technology used to see where a person is looking on a computer screen. It can also be used to control a computer with your eyes instead of using a traditional keyboard and mouse, enabling individuals with physical and cognitive conditions to live richer and more independent lives.

Eye tracking for accessibility

There are different uses for eye tracking within the area of assistive technology:

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Speech generation

People who are unable to speak or use a body part in a controlled manner to operate a keyboard, mouse, or touch screen can use eye tracking to write messages using only their eyes and then have the computer speak those messages out loud.

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Computer access

Messages can also be sent via e-mail, text or video call since you can access all the functions of a Microsoft tablet or computer with gaze interaction. This makes it possible to stay in touch with friends, order a pizza, or write a thesis independently.

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Environmental control

Many appliances, such as TVs, air conditioners, and even doors, can be operated by infrared remote controls. People with limited movement can use their eye-controlled computer as a remote control and operate appliances with gaze interaction.

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Increased engagement

Eye tracking can be used as a tool for teachers, parents and assistants. With an eye tracker and a simple yet powerful app like Gaze Viewer, you can see where someone is looking, or not looking, on a screen and base conversations on this.

How does eye tracking work?

Illustration of how the Tobii Dynavox eye tracker works


  1. The eye tracker sends out near infrared light.
  2. The light is reflected in your eyes.
  3. Those reflections are picked up by the eye tracker’s cameras.
  4. Through filtering and calculations, the eye tracker knows where you are looking.

As simple as the concept may be, an enormous amount of research and development has gone into Tobii Dynavox eye trackers to make them work in a simple and unobtrusive way.


For eye tracking to work as accurately as possible, the eye tracker must know more about your eyes. That's why you need to do a calibration, when the eye tracker measures how your eyes reflect light. The calibration is done by following a point or video that moves across the screen. The calibration data is combined with our unique 3D model of an eye to create an accurate eye tracking experience.

Illustration of how the Tobii Dynavox eye tracker calibrates the eyes

 Man uses a Tobii Dynavox device with eye tracking to click and choose an object on the screen


There are two ways of clicking when using gaze interaction. The method available depends on the application you use as well as your abilities:

  1. Dwell: A click occurs after focusing your eyes on a specific area for a predetermined number of milliseconds.
  2. Switch: Look where you want to click, and then press a switch to perform the click.

What makes Tobii Dynavox’s eye trackers unique?

Young girl who can move around freely when using the Tobii Dynavox I-Series

Free head movement

Our eye trackers use a unique and very accurate 3D model of a human eye. This model holds information about the physical shape of an eye and how light is reflected and refracted, among other things. With this model you don’t need to keep your head still when using a Tobii Dynavox eye tracker, in fact you can move your head freely without any significant loss of precision or accuracy. This is particularly beneficial for individuals with uncontrolled head movement, such as those with cerebral palsy or individuals with ALS who might adjust their position throughout the day.

Pupil tracking

For accurate eye tracking, the eye tracker needs to find your pupils (or more precisely, the relationship between the pupils and the glints, or reflections). This can be done through either bright or dark pupil tracking. Bright pupil tracking works similarly to when you get red eyes when using a camera with a flash. By placing the flash, or in this case the illuminators, farther away from the lens you can avoid this. This is dark pupil tracking.

Illustration of how the Tobii Dynavox eye tracker calibrates the eyes by bright and dark pupil tracking

Young boy using Tobii Dynavox I-Series device with her eyes

Works with most eyes

Some people track better with dark pupil tracking, others with bright pupil tracking. Factors like pupil size, age and environmental lights affect how well you are tracked using either of the two methods. Tobii Dynavox eye trackers are unique in that they dynamically switch between bright and dark pupil tracking, so you will always have an optimized eye tracking experience.

The Tobii Dynavox eye tracking advantage

Our eye tracking technology is designed with the following in mind:

Teen communicating using a Tobii Dynavox eye tracking device


Even though eye tracking may be a simple concept, it's a very complex and research-intense endeavor to make a product that's easy to use. We strive to make our eye tracking technology as simple to use as possible.


We have many years of experience with eye tracking technology. This includes the development of outdoor eye tracking - the industry’s first eye tracker dedicated specifically to accessibility, with the ability to control a device outdoors in bright sunlight.

Basketball practice coached with a Tobii Dynavox eye tracking device