An optical coherence tomography instrument is disclosed. The instrument comprises an eyepiece for receiving at least one eye of a user, at least one target display visible through said eyepiece, and a light source that outputs light that is directed through the eyepiece to the user's eye. The instrument further comprises an interferometer configured to produce optical interference using light reflected from the user's eye, an optical detector disposed so as to detect said optical interference, and electronics coupled to the target display and said detector. The electronics are configured to provide an output based on optical coherence tomography measurements obtained using said interferometer, and to produce features on said target display of varying size and receive user responses to test a user's visual acuity.
