Spectral analysis of viscoelasticity of the human lens

J Refract Surg. 1999 Nov-Dec;15(6):714-6. doi: 10.3928/1081-597X-19991101-22.


Purpose: In the aging lens, two different structural changes become progressively apparent: loss of accommodation and formation of cataract. These changes are due to different alterations in lens structure taking place on a molecular scale.

Methods: For the characterization of liquids, gels, elastic bodies and solids, dynamic mechanical analysis (DMA) represents a non-destructive macroscopic analysis method with considerable sensitivity to microscopic structural changes. Spectra of the shear compliance (reciprocal shear modulus) of human lenses at different ages were measured in a wide frequency range (1 mHz to 1 kHz). By means of computer analysis, the parameters of the involved relaxation processes and the viscous flow were determined.

Results: The increase in cross-linking density was correlated with the disappearance of viscous flow in the measured spectra. The accumulation of high-molecular-weight aggregates was held responsible for the shift of the lower frequency relaxation process to lower frequencies with increasing stiffness, which is likely to be correlated with a prolonged accommodation time.

Conclusion: Dynamic mechanical analysis represents a useful method for the spectroscopic characterization and quantification of the changes in the macroscopic viscoelastic properties caused by molecular changes in cataract formation and loss of accommodation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Aging / physiology*
  • Cataract / pathology
  • Cataract / physiopathology*
  • Elasticity
  • Humans
  • Lens, Crystalline / anatomy & histology
  • Lens, Crystalline / physiology*
  • Middle Aged