Not at all. In fact you should always wait until eye contact. I can't count the number of times I wish I had stared down a boss to make him/her understand that I was drowning in boredom only instead to give a quick smile and nod while continuing to look at my monitor.

It is way to easy to do "manager drive-by" and get absolutely no sense of reality from employees.

This is on both sides to get right. The manager waiting, and the employee taking the time to "look them in the eye".