title: Accommodative movements of the vitreous membrane, choroid, and sclera in young and presbyopic human and nonhuman primate eyes.
abstract: OBJECTIVE
  We report, for the first time to our knowledge, dynamic movements of the vitreous membrane and peripheral choroid during accommodation, and age-related changes in the anterior sclera.
  
  
  METHODS
  We studied 11 rhesus monkeys (ages 6-27 years) and 12 human subjects (ages 19-65 years). Accommodation was induced pharmacologically in human subjects and by central electrical stimulation in the monkeys. Ultrasound biomicroscopy, endoscopy, and contrast agents were used to image various intraocular structures.
  
  
  RESULTS
  In the monkey, the anterior hyaloid membrane bows backward during accommodation in proportion to accommodative amplitude and lens thickening. A cleft exists between the pars plicata region and the anterior hyaloid membrane, and the cleft width increases during accommodation from 0.79 ± 0.01 mm to 1.01 ± 0.02 mm in young eyes (n = 2, P < 0.005), as fluid from the anterior chamber flows around the lens equator toward the cleft. In the older eyes the cleft width was 0.30 ± 0.19 mm, which during accommodation increased to 0.45 ± 0.20 mm (n = 2). During accommodation the ciliary muscle moved forward by approximately 1.0 mm, pulling forward the choroid, retina, vitreous zonule, and the neighboring vitreous interconnected with the vitreous zonule. Among the humans, in the older eyes the scleral contour bowed inward in the region of the limbus, compared to the young eyes.
  
  
  CONCLUSIONS
  The monkey anterior hyaloid bends posteriorly during accommodation in proportion to accommodative amplitude and the sclera bows inward with increasing age in both species. 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, Wisconsin 53792-3220, USA. macroft@wisc.edu
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Croft
authors.forename: T Michael
authors.initials: TM
authors.lastname: Nork
authors.forename: Jared P
authors.initials: JP
authors.lastname: McDonald
authors.forename: Alexander
authors.initials: A
authors.lastname: Katz
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; D000818:Animals; D002829:Choroid / Q000000981:diagnostic imaging / Q000503:physiopathology*; D018450:Disease Progression; D004724:Endoscopy / Q000379:methods; D005260:Female; D006801:Humans; D007908:Lens, Crystalline / Q000503:physiopathology; D008253:Macaca mulatta / Q000502:physiology*; D008297:Male; D033401:Microscopy, Acoustic; D008875:Middle Aged; D057972:Posterior Eye Segment / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D011305:Presbyopia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D015203:Reproducibility of Results; D012590:Sclera / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014822:Vitreous Body / Q000000981:diagnostic imaging / Q000503:physiopathology*; D055815:Young Adult
keywords: accommodation; choroid; lens; presbyopia; vitreous membrane