An eye tracking system comprising an image display comprising: a first coordinate frame and configured to display an image of a surgical field comprising a second coordinate frame to a user, wherein the user is in a third coordinate frame, the image display configured to emit a light in a first wavelength range; a right eye tracker and a left eye tracker configured to emit light in a second wavelength range and to measure data about a first gaze point of the eyes of the user; an optical assembly between the image display and the right and left eyes of the user, the optical assembly configured to direct the light of the first and second wavelength ranges such that the light of the first and second wavelengths share at least a portion of optical paths between the eyes of the user and the image display; and at least one processor.