Sentence:  If we tilt the head to the right, the right eye will <WSD>intort</WSD> and the left eye will extort....So, if the right eye <WSD>intorts</WSD>, it means the superiors in that eye (RSR and RSO) work and if the left eye extorts it means the inferiors of that eye (LIO and LIR) work. 
Meaning of the word marked with <WSD> tags:  To twist inwards.