title: Accommodative changes in lens diameter in rhesus monkeys.
abstract: OBJECTIVE
  Some debate surrounds the accommodative mechanism in primates, particularly whether the lens equatorial diameter increases or decreases during accommodation. This study has been undertaken to measure the relationship between changes in lens diameter and refraction during accommodation in rhesus monkeys.
  
  
  METHODS
  Photorefraction was used to measure accommodation, and goniovideography was used to measure accommodative changes in lens diameter in the iridectomized eyes of two rhesus monkeys. Accommodation was stimulated through the full amplitude available to each eye by stimulation of the Edinger-Westphal nucleus of the brain. Dynamic measurement of refractive changes followed by dynamic measurements of changes in lens diameter for the same stimulus current amplitudes allow the relationship between refraction and lens diameter to be determined.
  
  
  RESULTS
  Lens diameter decreased relatively linearly during accommodation by 0.055 mm/diopter (D), resulting in an overall decrease in lens diameter of approximately 7% of the unaccommodated lens diameter for approximately 12 D of accommodation.
  
  
  CONCLUSIONS
  The rhesus monkey lens diameter decreases systematically with the refractive change during accommodation in accordance with the Helmholtz accommodative mechanism and in contrast to the accommodative mechanism originally proposed by Tscherning.
authors.affiliation: College of Optometry, University of Houston, Houston, Texas 77204-2020, USA. aglasser@uh.edu
authors.forename: Adrian
authors.initials: A
authors.lastname: Glasser
authors.forename: Mark
authors.initials: M
authors.lastname: Wendt
authors.forename: Lisa
authors.initials: L
authors.lastname: Ostrin
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000818:Animals; D005133:Eye Movements / Q000502:physiology; D032801:Iridectomy; D007498:Iris / Q000502:physiology / Q000601:surgery; D007908:Lens, Crystalline / Q000502:physiology*; D008253:Macaca mulatta; D012029:Refraction, Ocular / Q000502:physiology; D014741:Video Recording