title: Extralenticular and lenticular aspects of accommodation and presbyopia in human versus monkey eyes.
abstract: OBJECTIVE
  To determine if the accommodative forward movements of the vitreous zonule and lens equator occur in the human eye, as they do in the rhesus monkey eye; to investigate the connection between the vitreous zonule posterior insertion zone and the posterior lens equator; and to determine which components-muscle apex width, lens thickness, lens equator position, vitreous zonule, circumlental space, and/or other intraocular dimensions, including those stated in the objectives above-are most important in predicting accommodative amplitude and presbyopia.
  
  
  METHODS
  Accommodation was induced pharmacologically in 12 visually normal human subjects (ages 19-65 years) and by midbrain electrical stimulation in 11 rhesus monkeys (ages 6-27 years). Ultrasound biomicroscopy imaged the entire ciliary body, anterior and posterior lens surfaces, and the zonule. Relevant distances were measured in the resting and accommodated eyes. Stepwise regression analysis determined which variables were the most important predictors.
  
  
  RESULTS
  The human vitreous zonule and lens equator move forward (anteriorly) during accommodation, and their movements decline with age, as in the monkey. Over all ages studied, age could explain accommodative amplitude, but not as well as accommodative lens thickening and resting muscle apex thickness did together. Accommodative change in distances between the vitreous zonule insertion zone and the posterior lens equator or muscle apex were important for predicting accommodative lens thickening.
  
  
  CONCLUSIONS
  Our findings quantify the movements of the zonule and ciliary muscle during accommodation, and identify their age-related changes that could impact the optical change that occurs during accommodation and IOL function.
authors.affiliation: Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53792-3220, USA. macroft@wisc.edu
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Croft
authors.forename: Jared P
authors.initials: JP
authors.lastname: McDonald
authors.forename: Alexander
authors.initials: A
authors.lastname: Katz
authors.forename: Ting-Li
authors.initials: TL
authors.lastname: Lin
authors.forename: Elke
authors.initials: E
authors.lastname: Lütjen-Drecoll
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; D002924:Ciliary Body / Q000000981:diagnostic imaging / Q000503:physiopathology*; D004195:Disease Models, Animal; D005260:Female; D006801:Humans; D007908:Lens, Crystalline / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008253:Macaca mulatta; D008297:Male; D033401:Microscopy, Acoustic; D008875:Middle Aged; D011305:Presbyopia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014822:Vitreous Body / Q000000981:diagnostic imaging / Q000503:physiopathology*; D055815:Young Adult
keywords: accommodation; ciliary muscle; human; lens; presbyopia