The mechanism of lenticular accommodation in chicks

Adrian Glasser, Christopher J Murphy, David Troilo, Howard C. Howland

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


In the chick eye, accommodation for near objects is brought about by changes in the focal length of the lens and by changes in the corneal radius of curvature. Several different mechanisms of lenticular accommodation have been proposed for the avian eye. These include a role for the ciliary muscle, a role for the iris muscle, and a role for changes in intraocular pressure. We have studied accommodation in the chick eye using electrical stimulation of the Edinger-Westphal nucleus, electric-field stimulation of enucleated eyes, in vitro measurement of changes in back vertex distance of the lens, and histology. We prcsent evidence showing that, in the chick eye, lenticular accommodation is induced primarily by a contraction of the muscle fibers at the peripheral edge of the iris. During accommodation, the peripheral muscle fibers of the iris contract to apply a force through the ciliary processes to the anterior equatorial surface of the lens. This increases the focal power of the lens. When accommodation is relaxed, the lens is returned to its unaccommodated state by the elasticity of the pectinate ligament and the ciliary body. Contractions of the posterior ciliary muscle and changes in intraocular pressure, forces that have previously been proposed to play major roles in lenticular accommodation, are shown to be of secondary importance only.

Original languageEnglish (US)
Pages (from-to)1525-1540
Number of pages16
JournalVision Research
Issue number11
StatePublished - 1995
Externally publishedYes


  • Chick
  • Ciliary muscle
  • Edinger-Westphal nucleus
  • Iridectomy
  • Iris
  • Lens

ASJC Scopus subject areas

  • Ophthalmology
  • Sensory Systems


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