Annals of Biomedical Engineering

, Volume 35, Issue 9, pp 1608–1616 | Cite as

An Indentation Technique to Characterize the Mechanical and Viscoelastic Properties of Human and Porcine Corneas

  • Mark Ahearne
  • Ying Yang
  • Kong Y. Then
  • Kuo-Kang Liu


Cornea is a load-bearing tissue whose mechanical and viscoelastic characteristics are not well understood, due to the challenge associated with most of the measurements. A novel indentation technique has been developed for mechanical characterization of human and porcine corneal tissue, using a tailored depth-sensing microindentation instrument. During indentation, the corneas were suspended by clamping the edges of the cornea, thus allowing depth-sensing measurement free from the complication of the backing substrate. The deformation displacement and the amount of force applied by the indenter were used to obtain hysteresis and stress relaxation data for both human and porcine corneas. Optical coherence tomography was used to measure the thickness of the cornea. Simple theoretical analyses have been undertaken to explain the loading–unloading and the stress relaxation data. The effect of swelling on the mechanical properties of the cornea was also examined. Porcine corneas appeared to be less stiff and to demonstrate more linear response than human corneas under loading. More importantly, it is shown that swelling reduced the strength of the corneas. Our results demonstrate that this new indentation system can be used to characterize the mechanical and viscoelastic properties of corneas.


Instrumentation Stress relaxation Hysteresis Biomechanics 



The authors are grateful for the finical support provided by the North Staffordshire R&D Consortium and to Dr Pierre Bagnaninchi for his help with OCT measurements.


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Copyright information

© Biomedical Engineering Society 2007

Authors and Affiliations

  • Mark Ahearne
    • 1
  • Ying Yang
    • 1
  • Kong Y. Then
    • 2
  • Kuo-Kang Liu
    • 1
  1. 1.Institute of Science and Technology in Medicine, School of MedicineKeele UniversityStoke-on-TrentUK
  2. 2.Birmingham and Midland Eye CentreCity HospitalBirminghamUK

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