Facebook has acquired Eye Tribe, a Danish start-up that specializes in eye tracking technology, in order to bring the technology to the Oculus’ virtual reality system.

Eye Tribe was founded in 2011 to develop eye-tracking technology. The company has produced an API that allows software developers to build eye tracking into their applications and a $199 consumer product called the Eye Tribe Tracker Pro.

Eye tracking has the potential to bring enhancements to virtual reality. The eye tracking applications are divided into 2 categories: active and passive.

An eye tracker enables users to use their eye movements as an input modality to control a device, an application, a game, etc. The user’s eye gaze point can be combined with other input modalities like buttons, keyboards, mouse or touch, in order to create a more natural and engaging interaction.

For example, fully rendering only the area of the image where the viewer is looking can reduce the computational power needed to bring deeply immersive VR to consumer systems.

Through active tracking, a display could scroll when the user's eyes reach the sides of the screen. Or an onscreen keyboard would allow people with motor disabilities to enter text, email or chat.

Facebook may be more interested in what Eye Tribe calls passive tracking. Passive eye tracking records where a person looks and how long they look at a specific location. The technology is usually advertised as a method for making user interfaces more friendly and website displays more effective from a marketing perspective.