title: Accommodative movements of the lens/capsule and the strand that extends between the posterior vitreous zonule insertion zone & the lens equator, in relation to the vitreous face and aging.
abstract: OBJECTIVE
  To elucidate the dynamic accommodative movements of the lens capsule, posterior lens and the strand that attaches to the posterior vitreous zonule insertion zone and posterior lens equator (PVZ INS-LE), and their age-related changes.
  
  
  METHODS
  Twelve human subjects (ages 19-65 years) and 12 rhesus monkeys (ages 6-27 years) were studied. Accommodation was induced pharmacologically (humans) or by central electrical stimulation (monkeys). Ultrasound biomicroscopy was used to image intraocular structures in both species. Surgical procedures and contrast agents were utilized in the monkey eyes to elucidate function and allow visualization of the intraocular accommodative structures.
  
  
  RESULTS
  Human: The posterior pole of the lens moves posteriorly during accommodation in proportion to accommodative amplitude and ciliary muscle movement. Monkey: Similar accommodative movements of the posterior lens pole were seen in the monkey eyes. Following extracapsular lens extraction (ECLE), the central capsule bows backward during accommodation in proportion to accommodative amplitude and ciliary muscle movement, while the peripheral capsule moves forward. During accommodation the ciliary muscle moved forward by ~1.0 mm, pulling forward the vitreous zonule and the PVZ INS-LE structure. During the accommodative response the PVZ INS-LE structure moved forward when the lens was intact and when the lens substance and capsule were removed. In both the monkey and the human eyes these movements declined with age.
  
  
  CONCLUSIONS
  The accommodative shape change of the central capsule may be due to the elastic properties of the capsule itself. For these capsule/lens accommodative posterior movements to occur, the vitreous face must either allow for it or facilitate it. The PVZ INS-LE structure may act as a 'strut' to the posterior lens equator (pushing the lens equator forward) and thereby facilitate accommodative forward lens equator movement and lens thickening. The age-related posterior restriction of the ciliary muscle, vitreous zonule and the PVZ-INS LE structure dampens the accommodative lens shape change. Future descriptions of the accommodative mechanism, and approaches to presbyopia therapy, may need to incorporate these findings.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, USA.
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Croft
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, USA.
authors.forename: Gregg
authors.initials: G
authors.lastname: Heatley
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, USA.
authors.forename: Jared P
authors.initials: JP
authors.lastname: McDonald
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Katz
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, USA.|Wisconsin National Primate Research Center, University of Wisconsin-Madison, Madison, USA.|McPherson Eye Research Institute, University of Wisconsin-Madison, Madison, USA.
authors.forename: Paul L
authors.initials: PL
authors.lastname: Kaufman
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D007903:Lens Capsule, Crystalline / Q000502:physiology*; D007908:Lens, Crystalline / Q000502:physiology*; D008253:Macaca mulatta; D008297:Male; D008875:Middle Aged; D011305:Presbyopia / Q000503:physiopathology*; D014822:Vitreous Body / Q000502:physiology*; D055815:Young Adult
keywords: accommodation; capsule; lens; presbyopia