• Located at the center of the iris, the pupil is the mobile aperture through which light enters the eye. Changes in pupillary diameter, controlled by the balance of parasympathetic and sympathetic innervation, adjust retinal illumination and the depth of focus of the eye. Pupil constriction (miosis) occurs in response to: (1) increases in retinal illumination; (2) drowsiness, fatigue, or decreased alertness; and (3) near viewing as part of the near triad of convergence, accommodation, and pupil constriction. Pupil dilation (mydriasis) occurs both in response to decreases in ambient lighting and to alerting stimuli or excitement. Depending on the relative balance of these conditions, pupil diameter can vary between 1 and 9. mm in normal individuals.
  • Authors

    Digital Object Identifier (doi)

    International Standard Book Number (isbn) 13

  • 9780123851581
  • Start Page

  • 1014
  • End Page

  • 1016