A ring of smooth muscle fibers located close to the pupillary margin, a little anterior to the iris’ epithelium. It encircles the pupil and constricts the pupil in bright light during accommodation or pupillary light reflex.

Also Known As

  • Iris Sphincter Muscle
  • Pupillary Sphincter
  • Pupillary Constrictor
  • Circular Muscle of Iris
  • Circular Fibers