The iris has two surfaces and two margins:

Anterior surface (Read more!) - a rough surface that faces the cornea;
Posterior surface (Read more!) - a relatively smooth surface that faces the lens;
Pupillary margin - the inner border that surrounds the pupil;
- Pupillary ruff (pupillary frill) - a dark, serrated fringe of pigment that represents the anterior termination of the pigmented epithelium from the posterior iris; its pigmentation helps reduce stray light entering the eye;
Ciliary margin - the outer border that connects to the ciliary body; also known as the root of the iris; the iris is thinnest at its root.

Additionally, the iris also contains a rich network of blood vessels forming two arterial circles - the major arterial circle near the ciliary margin and the minor arterial circle near the pupillary margin. These circles are formed by branches of the anterior ciliary arteries and the long posterior ciliary arteries.

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Surfaces and margins of iris