are "the mirrors of the soul", the "traintors of the heart". The importance of continuos eye contact cannot be overestimated.
Try to give every person 2- 3 seconds eye contact, no matter what the size of your audience. The main reason is to assess their understanding and concentration levels. With a flexible approach and good planning this will allow you to amend your content to meet the needs that you observe.
The audience will also be encouraged to pay attention and are more likely to ask relevant questions.