Also, there is a difference between a side pass and a leg yield. In a side pass the horse's head is slightly bent in the direction of travel where in the leg yield, the head is slightly bent opposite the direction of travel. As MILDOT indicated, just so you can see the close edge of the eye.
ie, leg yield to the left, the head is bent right..sidepass to the left, the head is bent to the left.
The idea in a side pass and leg yield is that the front and hind legs will cross over each other in the forward travel. If you don't have that cross over, you don't have a correct leg yield or sidepass.