Eye-tracking allows to detect and follow the eye movements of a user. It is a technology initially used in scientific research and in the field of marketing. In virtual reality, eye-tracking allows to know where the user has looked, where in the virtual environment he has paid the most attention. This is useful data for advertisers and trainers in particular. Eye-tracking can also be used to create more realistic virtual reality experiences, such as reproducing eye movement on an avatar. It is also an interesting technology to build more natural interactions, by triggering commands with the eyes. Finally, combined with foveal rendering, eye-tracking allows to have an image rendering close to the human eye.