Ch_06.qxd 18/08/2004 09:35 AM Page 59
Chapter
6 Neuro-Ophthalmology
Thomas E. Bournias, MD
Pupil
The pupil is the central portion of the iris plane. It both constricts (miosis) and dilates (mydriasis). Mydriasis is controlled by the dilator muscle, which is controlled primarily by sympathetic innervation. Miosis is controlled by the sphincter muscle, which primarily receives parasympathetic innervation.