The eye position detector monitors {HEAD ~ light} reflected from {TAIL ~ the users eye} to identify the pupil position 
reflected from
The eye position detector monitors { HEAD ~ light } reflected from { TAIL ~ the users eye } to identify the pupil position
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH