Popping off one of the two IR emitter rings, we find the elusive eye-tracking IR camera hiding behind a dark filter.

These appear to be OmniVision CameraCubeChip cameras with externally-mounted dichroic filters.

Eye tracking in VR and AR allows for some pretty cool new interface options, as well as improvements in realism and rendering efficiency.

Placing a single camera below each eye may limit the accuracy and range of eye tracking—the camera can better view the eye/pupil when the user is looking downward than upward.