The natural upper eyelid crease is called the supratarsal fold or crease. This crease occurs just above the upper border of a stiff structure called the tarsus. The tarsus provides structural integrity to the lower aspect of the upper eyelid so that it has stiffness and so that it does not flop around. This crease is created by the extension of the eyelid lifting muscle, called the levator, as it attaches to the skin.