Inner zone of iris
Anulus minor iridis
- Latin synonym: Zona pupillaris iridis
- Synonym: Pupillary zone of iris
- Related terms: Inner border of iris
Definition
The inner zone of iris (a.k.a. the lesser ring of the iris or the pupillary zone) is the inner, narrow, coarsely striated, concentric pupillary zone on the anterior surface of the iris, more delicate than the greater ring.
It should be distinguished from the pupillary margin, which is the inner edge of the pupil, whereas the pupillary (inner) zone is the region of the iris extending from that edge to the collarette.
The inner (pupillary) zone contains the sphincter pupillae muscle, which lies circumferentially near the pupillary margin.
References
Standring, S. (Ed.). (2015). Eye (Chapter 42). In Gray's anatomy: The anatomical basis of clinical practice (41st ed., pp. 686-706). Churchill Livingstone.
