An instrument is proposed for examining or machining a human eye, with an eye-tracker for acquiring eye movements and for outputting a signal that is representative of the acquired eye movements, the eye-tracker including an interferometric image-acquisition device that has been set up for time-resolved acquisition of sectional images of the eye and that operates on the basis of two-dimensional or three-dimensional optical coherence tomography, and also an evaluating module ascertaining the eye movements solely from the sectional images.