pupil (P)

Introduction

The circular opening in the center of the iris, through which light rays enter the eye.

Pupillary size

• 2-4 mm in diameter in bright light (adults)
• 4-8 mm in the dark
• pupils are generally equal in size

Determinants of pupillary size

• afferent input from the optic nerves, optic chiasm & optic tracts
• efferent output of sympathetic nervous system
• efferent output of the parasympathetic nervous system

More general terms

• eye structure

Additional terms

• anisocoria
• fixed & dilated pupils
• Horner's (Bernard-Horner's) syndrome
• Marcus Gunn pupil (afferent pupillary defect)
• miosis (pupillary constriction)
• mydriasis