title: Optomechanical response of human and monkey lenses in a lens stretcher.
abstract: OBJECTIVE
  To quantify the forces necessary to change the shape and optical power of human and monkey lenses.
  
  
  METHODS
  Cynomolgus monkey (n = 48; age: 3.8-11 years), rhesus monkey (n = 35; age: 0.7-17 years) and human (n = 20, age 8-70 years) eyes obtained postmortem, including the lens, capsule, zonules, ciliary body, and sclera were mounted in an optomechanical lens-stretching system. Starting at zero load, the lenses were symmetrically stretched in a stepwise fashion in 0.25- or 0.5-mm steps. The load, lens diameter, inner ciliary body diameter, and lens power were measured at each step and the diameter- and power-load responses were quantified.
  
  
  RESULTS
  The diameter- and power-load responses were found to be linear in the physiologically relevant range of stretching. The average change in cynomolgus, rhesus, and human lens diameter, respectively, was 0.094, 0.109, and 0.069 mm/g in young lenses, and 0.069, 0.067, and 0.036, mm/g in older lenses. For the same lenses, the average change in lens power was -3.73, -2.83, and -1.22 D/g in young lenses and -2.46, -2.16, and -0.49 D/g in older lenses.
  
  
  CONCLUSIONS
  The force necessary to change the lens diameter and lens power increases with age in human and monkey lenses. The results agree with the Helmholtz theory of accommodation and with presbyopia theories that predict that the force required to disaccommodate the lens increases with age.
authors.affiliation: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida 33136, USA. fmanns@miami.edu
authors.forename: Fabrice
authors.initials: F
authors.lastname: Manns
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Parel
authors.forename: David
authors.initials: D
authors.lastname: Denham
authors.forename: Christian
authors.initials: C
authors.lastname: Billotte
authors.forename: Noel
authors.initials: N
authors.lastname: Ziebarth
authors.forename: David
authors.initials: D
authors.lastname: Borja
authors.forename: Viviana
authors.initials: V
authors.lastname: Fernandez
authors.forename: Mohammed
authors.initials: M
authors.lastname: Aly
authors.forename: Esdras
authors.initials: E
authors.lastname: Arrieta
authors.forename: Arthur
authors.initials: A
authors.lastname: Ho
authors.forename: Brien
authors.initials: B
authors.lastname: Holden
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D000818:Animals; D002648:Child; D002924:Ciliary Body / Q000033:anatomy & histology / Q000502:physiology; D006801:Humans; D007908:Lens, Crystalline / Q000033:anatomy & histology / Q000502:physiology*; D008252:Macaca fascicularis; D008253:Macaca mulatta; D008875:Middle Aged; D012029:Refraction, Ocular / Q000502:physiology*; D013314:Stress, Mechanical; D014019:Tissue Donors