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Original article
Viscoelastic properties of fresh human lenses under 40 years of age: implications for the aetiology of presbyopia
  1. Ronald A Schachar1,
  2. Roger W Chan2,3,
  3. Min Fu4
  1. 1Department of Physics, University of Arlington, Arlington, Texas, USA
  2. 2Department of Otolaryngology—Head and Neck Surgery, University of Texas, Southwestern Medical Center, Dallas, Texas, USA
  3. 3Department of Biomedical Engineering, University of Texas, Southwestern Medical Center, Dallas, Texas, USA
  4. 4Depatment of Neurology, UT Southwestern Medical Center, Dallas, Texas, USA
  1. Correspondence to Professor Ronald A Schachar, PO Box 8669, La Jolla, CA 92038, USA; ron{at}2ras.com

Abstract

Aim To determine the viscoelastic properties of fresh human lenses obtained from cadavers under 40 years of age.

Methods 52 intact clear, human lenses were obtained from 26 donors (mean age of 27.5±9.2 years) within 9±4 h of death. The viscoelastic properties of the lens nuclei and 16 of the lens cortices were quantified within 42±10 h of death using a controlled-strain, linear, simple-shear rheometer.

Results The means (±SD) of the viscoelastic properties of the lens nuclei at a frequency of 75 Hz were: elastic shear modulus, G′=11.00±4.67 Pa, viscous shear modulus, G′′=24.91±10.98 Pa, magnitude of the complex shear modulus, |G*|=27.23 Pa, dynamic viscosity, η′=0.33 Pa.s, damping ratio, ζ=2.26 and phase shift, δ=66.17°. There was no statistical difference in these measures between the lens cortices and their respective lens nuclei. There was a small age-related statistically significant increase in G′, p=0.003, but not G′′ or |G*|.

Conclusions The observed age-related increase in tissue stiffness of the lens nucleus, ∼0.4 Pa/year, is too small to account for the 10 dioptre decline in accommodative amplitude in this age group.

  • Human crystalline lens
  • material properties
  • elastic shear modulus
  • viscous shear modulus
  • complex shear modulus
  • dynamic viscosity
  • damping ratio
  • phase shift
  • presbyopia
  • lens and zonules
  • experimental and laboratory

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Footnotes

  • Funding Partially supported by a grant from the National Institutes of Health, NIDCD Grant no R01 DC006101.

  • Competing interests None.

  • Ethics approval Ethics approval was provided by the Eye-Bank for Sight Restoration, New York.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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