How often have you ordered your child to "Look at me!" when what you really wanted him or her to do was listen? Eye contact is such a powerful connection that we believe we must have it to get our message across. When a child won't make eye contact, it's hard not to consider it as willful resistance, or at the very least inattentiveness.
But there can be times when, quite frankly, eye contact is not only not essential, but actively harmful in getting your message through. If making eye contact is difficult for your child, forcing it is going to focus all of his or her attention and effort on that one act -- not on the verbal message you're trying to get across. And if processing is a problem for your child, adding visual processing into the mix with auditory processing can make it that much harder for a verbal message to get through. What you want is to focus attention on the specific skills you need, not spread it out.
So, if what you want is for your child to listen to you, say just that: "Listen to me." Your child may actually turn his face away or bow her head in order to do that, but if you've got an ear to you, you're in business. As long as your child does in fact listen and respond, don't sweat the eye contact. There's something to be said for being all ears.