Which layer of the eye completely surrounds the eye except for a dark, round opening called the pupil?

The layer of the eye that completely surrounds the eye except for a dark, round opening called the pupil, is the uvea. The uvea is also the pigmented area of the person's eye. So when people that a person has a brown, blue, or green eyes, they are referring to the uvea's color.

Atissue is a group of connected cells that have a similar function within an organism.