Methods, systems, and devices are disclosed for optical sensing and tracking of eye movement. In one aspect, a method for tracking the movement of an eye includes emitting a first modulated light and a second modulated light toward an eye of a user, wherein the first modulated light and the second modulated light have substantially the same modulation frequency, but the modulation phases of the two modulated lights are substantially opposite to each other receiving at a photodetector module a returned light including at least a partial retroreflected light from the eye of the user based on the first and second modulated lights and processing the output signal from the photodetector module to determine positional and dimensional parameters of the eye of the user based at least on the partial retroreflected light corresponding to the first and second modulated lights.
