A preliminary path (410) for light travelling towards a camera (302) via corneal reflection (116) is estimated based on a preliminary position (109) and orientation (112) of an eye (100). A position (502) where the reflection would appear in images (500) captured by the camera is estimated. A distance (503) is formed between a detected position (501) of a corneal reflection of an illuminator (301) and the estimated position. A second preliminary path (810) for light travelling through the cornea (106) or from the sclera (117) towards a camera (302) is estimated based on the preliminary position and orientation, and a position (902, 905) where the second preliminary path would appear to originate in images (900) captured by this camera is estimated. A distance (903, 906) is formed between a detected edge (901, 904) of a pupil (103) or iris (101) and the estimated position where the second preliminary path would appear to originate. An updated position and/or orientation of the eye is determined using an objective function formed based on the formed distances.
