Systems and methods for measuring visual axis of the eye

A computer program product comprising a non-transitory computer readable medium having instructions recorded thereon, the instructions when executed by a computer implementing a method comprising:

• while a person's head is at a first pose and the person's eye is gazing at a point in a 3D space, obtaining a first orientation of the eye with respect to an image sensor and a first orientation of a spatial orientation sensor with respect to the 3D space;
• while the person's head is at a second pose and the person's eye is gazing at the point, obtaining a second orientation of the eye with respect to the image sensor and a second orientation of the spatial orientation sensor with respect to the 3D space;
• wherein the first pose and the second pose are different;
• determining an angular offset between a visual axis of the eye and an optical axis of the eye, or an angular offset between a line of sight of the eye and the optical axis of the eye, based on:
• the first orientation of the eye,
• the first orientation of the spatial orientation sensor,
• the second orientation of the eye,
• the second orientation of the spatial orientation sensor, and
• an orientation of the image sensor relative to the spatial orientation sensor or an orientation of the spatial orientation sensor relative to the image sensor;
• wherein the image sensor and the spatial orientation sensor do not move relative to each other.