title: Accommodative ciliary body and lens function in rhesus monkeys, I: normal lens, zonule and ciliary process configuration in the iridectomized eye.
abstract: OBJECTIVE
  The underlying causes of presbyopia, and the functional relationship between the ciliary muscle and lens during aging are unclear. In the current study, these relationships were studied in rhesus monkeys, whose accommodative apparatus and age-related loss of accommodation are similar to those in humans.
  
  
  METHODS
  Centripetal ciliary body and lens equator movements were measured during accommodation in 28 eyes of 21 rhesus monkeys (ages, 5.7-26 years) by goniovideography. Ultrasound biomicroscopy was performed in 21 eyes of 17 monkeys. Narrowing of the angle between the anterior aspect of the ciliary body and the inner aspect of the cornea was used as a surrogate indicator of forward ciliary body movement during accommodation.
  
  
  RESULTS
  Average centripetal ciliary body movement in older eyes (age > or =17 years, n = 16) was approximately 20% (0.09 mm) less than in young eyes (age, 6-10 years, n = 6), but not enough to explain the 60% (0.21 mm) loss in centripetal lens movement nor the 76% (10.2 D) loss in accommodative amplitude. Average forward ciliary body movement was 67% (49 degrees ) less in older (n = 11) versus young (n = 6) eyes. Maximum accommodative amplitude correlated significantly with the amplitude of centripetal lens movement (0.02 +/- 0.003 mm/D; n = 28; P < 0.001) and with forward ciliary body movement (3.34 +/- 0.54 deg/D; n = 21; P = 0.01).
  
  
  CONCLUSIONS
  Decreased lens movement with age could be in part secondary to extralenticular age-related changes, such as loss of ciliary body forward movement. Ciliary body centripetal movement may not be the limiting component in accommodation in the older eye.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Wisconsin Regional Primate Research Center, University of Wisconsin, Madison 53792-3284, USA. macroft@wisc.edu
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Croft
authors.forename: Adrian
authors.initials: A
authors.lastname: Glasser
authors.forename: Gregg
authors.initials: G
authors.lastname: Heatley
authors.forename: Jared
authors.initials: J
authors.lastname: McDonald
authors.forename: Timothy
authors.initials: T
authors.lastname: Ebbert
authors.forename: David B
authors.initials: DB
authors.lastname: Dahl
authors.forename: Nivedita V
authors.initials: NV
authors.lastname: Nadkarni
authors.forename: Paul L
authors.initials: PL
authors.lastname: Kaufman
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000375:Aging / Q000502:physiology*; D000818:Animals; D002924:Ciliary Body / Q000000981:diagnostic imaging / Q000502:physiology*; D005133:Eye Movements; D005260:Female; D006068:Gonioscopy; D032801:Iridectomy; D007908:Lens, Crystalline / Q000000981:diagnostic imaging / Q000502:physiology*; D008022:Ligaments / Q000000981:diagnostic imaging / Q000502:physiology*; D008253:Macaca mulatta / Q000502:physiology*; D008297:Male; D033401:Microscopy, Acoustic; D009130:Muscle, Smooth / Q000000981:diagnostic imaging / Q000502:physiology