Expectation Maximization to Determine Position of Ambient Glints

Exemplary embodiments may involve analyzing reflections from an eye to help determine where the respective sources of the reflections are located. An exemplary method involves: (a) analyzing eye-image data to determine observed movement of a reflected feature on an eye surface; (b) determining an expected movement of the reflected feature on the eye surface given a value of a z-distance parameter; (c) determining a difference between the observed movement of the reflected feature on the eye surface and the expected movement of the reflected feature on the eye surface; (d) if the difference is less than a threshold, then associating the value of the z-distance parameter with a source of the reflected feature; and (e) if the difference is greater than the threshold, then: (i) making a predetermined adjustment to the value of the z-distance parameter; and (ii) repeating (a) to (d) with the adjusted value of the z-distance parameter.