The musculature and pupillary response of the Great Horned Owl iris

Lynn W. Oliphant, Mark R. Johnson, Christopher J Murphy, Howard Howland

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


There is considerable confusion in the literature regarding the nature of the musculature of the avian iris. The most commonly held view is that both the sphincter and dilator are striated. The iris of the Great Horned Owl (Bubo virginianus) has a complex iridial musculature consisting of three circumferential components (a myoepithelium, smooth muscle and striated muscle) and two radial components (a well-developed myoepithelium and a few striated fibers). On the basis of the anatomy and relative development of these components, and a quantitative analysis of the pupillary reflex, it is proposed that the circumferential striated muscle is the primary pupillary constrictor and radial myoepithelium is the primary dilator. The annular band of smooth muscle may play an important role in maintaining pupillary size.

Original languageEnglish (US)
Pages (from-to)583-595
Number of pages13
JournalExperimental Eye Research
Issue number6
StatePublished - 1983
Externally publishedYes


  • avian iris
  • myoepithelium
  • pupillography
  • smooth muscle
  • striated muscle

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems


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