An in-flight entertainment system includes a video display unit facing a user seat. The video display unit includes a display surface that displays images to a user who is seated on the user seat. A light emitter illuminates eyes of the user. A camera outputs a video signal containing reflections from the illuminated eyes. A processor processes the video signal to determine a viewing location on the display surface at which the eyes are directed, and controls at least one function for how images are displayed on the display surface responsive to the determined viewing location.