Abstract: Methods and apparatus for correcting the gaze direction and the origin (entrance pupil) in gaze tracking systems. During enrollment after an eye model is obtained, the pose of the eye when looking at a target prompt is determined. This information is used to estimate the true visual axis of the eye. The visual axis may then be used to correct the point of view (PoV) with respect to the display during use. If a clip-on lens is present, a corrected gaze axis may be calculated based on the known optical characteristics and pose of the clip-on lens. A clip-on corrected entrance pupil may then be estimated by firing two or more virtual rays through the clip-on lens to determine the intersection between the rays and the corrected gaze axis.