Iris - general

Author: Nat Pernick, M.D. (see Authors page)

Revised: 23 May 2018, last major update February 2014

Copyright: (c) 2004-2018, PathologyOutlines.com, Inc.

PubMed Search: Iris [title] eye review[ptyp]

Cite this page: Pernick, N. Uvea: iris - general. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/eyeuveairisgeneral.html. Accessed December 13th, 2018.
Definition / general
  • Thin diaphragm of tissue with central opening (pupil)
  • Forms boundary of anterior and posterior chamber
  • Highly textured with folds and crypts
  • Part of middle layer of eye (also ciliary body and choroid)
  • Normally rests gently upon lens and bulges slightly forward
  • Consists of stroma and posterior epithelial lining (two closely apposed epithelial layers, with numerous melanosomes); contains sphincter muscle within stroma that controls pupil
  • Anterior iris lacks a cellular lining
  • Color is due to number of stromal melanocytes; blue irises have few stromal melanocytes; brown irises have numerous melanocytes
  • Blood vessels are usually surrounded by a thick collar of collagen fibers, resembling arteriolosclerosis
  • Fewer melanosomes and melanocytes in patients with ocular and oculocutaneous albinism
  • Regulates amount of light reaching pupil; muscles of iris dilate or constrict pupil in response to parasympathetic or sympathetic nerve impulses; normal diameter of pupil is 1 - 8 mm
  • Iridectomy: excision of small segment of iris; place on filter paper to avoid folding
  • Ectropion uveae: fibrovascular tissue on anterior surface of iris everts the papillary margin and pulls pigmented epithelia onto anterior surface of iris

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Iris: front view

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Choroid and iris

Microscopic (histologic) images

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Iris and ciliary body with open anterior chamber angle

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Normal iris

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Iris and lens