To me and many of the players I know, eye contact is a key element.  From the time who at first refuses to allow the sub to look up from the floor without permission to the intense use of eye contact during intense moments of pain, eye contact is a reward and a way to share the experience,  
I love to have a sub restrained while I simulate her and stare deep into here sys I bring he to the edge  and then back  off and repeat this.  It allows me to know where we are and how far to go.
Just recently Madam 9 approached me seductively (I never reviewed her and she deserves a great one so I  hope she won't mind) She stared seductively, affectionately,hypnotically into me eyes and while holding my stare brought a well placed knee which came so unexpectedly give the romanic stare that is set the perfect atmosphere for the rest of the lovely hours that followed.  
One of my ATF dommes would sit across me while I DATY and she kept me working devotedly with an expendable rectal insert and as I DATY, she stared into my very soul.  
One of my favorite subs who was into more pain than I am comfortable with  like to be ring gagged (I use these as breathing through the mouth is open) and used her eyes to beg and plead while I use her favorite  instruments on her.

Whether that is to withhold it or to insist on it...to command the attention to my eyes as you are consumed into the moment is an edging tool.