An eye tracking apparatus for monitoring the movement of a users eye, the apparatus including: a display for displaying an image an eye imaging sensor for monitoring the users eye and for providing an output indicative of the users point of regard in the users field of vision an optical combiner arranged, in use, in optical communication with the display, the eye imaging sensor and the users eye: said optical combiner arranged to receive the displayed image from the display, to project said image into the users field of vision, to receive electromagnetic radiation reflected from the users eye and to pass said reflected radiation to the eye imaging sensor wherein the optical combiner is adapted to substantially correct for aberrations in the reflected radiation introduced therein by the optical combiner.
