The lamp of the body is the eye. If your eye is sound, your whole body will be filled with light: Matthew 6:22
A sound eye is a natural eye: not one that lectors use deliberately to try to connect with the assembly. When our eye contact is forced, its pretense easily shows.
The eye contact we make with our spouse or best friend over coffee, when serving meals to the homeless or when counseling a child may seem like a good thing to do from the ambo, but unless we're highly skilled at it, we're better off to avoid it.
Some worshippers get uncomfortable when we single them out, others may feel flattered, and others as if we're seeking approval from them for our performance; all feelings that can distract them from hearing the word of God we're proclaiming.
The biggest risk of too much individual eye contact is the exclusion of the rest of the assembly. There's no way the worshippers in the back rows will feel that they're being "gathered in" to hear God's word if we're only peeking up at a few people in the front rows.
The better way to make our listeners feel assured that they're being included is with area contact: to look up one side of the assembly from front to back, then down the center, back up the other side and so on. Caution must be taken, however, not to get into a fixed pattern where the assembly will start thinking about where we're going next instead of on the word of God.
We need to be unpredictable as to where our eyes are going next, move seamlessly from the lectionary to the assembly and back without bouncing up and down like a ferret, and keep our finger on the lectionary page where we're reading so we don't get lost when returning back to it.
With area contact, we'll likely find ourselves dropping our eyes down on a few individuals here and there. And this is fine so long as we keep moving along without locking on to anyone. With smaller assemblies as in a chapel at daily mass, area contact will give way to more "pew" contact, challenging us all the more not to rest ourselves on anyone's eyes too long.
Eye contact is important, but it is always secondary to effective proclamation. If we give eye contact priority at the expense of a poorly prepared reading, our listeners' experience will only be "skin deep."