Four key reasons to maintain strong eye-contact with your audience:

• Establishs personal connections with the audience.
• Audiences tend to distrust speakers who do not maintain eye contact.
• You can gauge audience reaction and then adapt your talk as necessary.
• Eye contact helps keep the audience attentive.
  

Helpful hints:

If you know that you keep losing eye-contact, put a hidden reminder in your slides or notes to remind yourself of eye contact.

Look at all parts of the audience, not at just one part of the room or a single person.  Divide the room into segments and force yourself to look at each segment.

Practice your talk until you no longer need to look at your notes.  Use them only when necessary, not out of nervousness.

Remember that if you turn your head to read from the screen, you completely lose eye-contact with your listeners.