If we have two eyes, why don’t we see double?

The direction of each of your eyes is controlled by three pairs of muscles connected to the outside of the eyeball. These are the most precisely controlled muscles of your body. They are controlled by nerve messages from the brain to keep your eyes pointed together.

Seeing begins with nerve messages sent by light-sensitive cells in the retina at the back of each eye and ending up in your brain. That all works so that your brain “sees” a picture of the little image that falls on the retina. And the eyes are pointed together so carefully that the same picture is formed by messages from your two eyes. That’s how you can use two eyes to see “single” and not “double.”