An Indentation Technique to Characterize the Mechanical and Viscoelastic Properties of Human and Porcine Corneas |
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Authors: | Mark Ahearne Ying Yang Kong Y Then Kuo-Kang Liu |
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Institution: | (1) Institute of Science and Technology in Medicine, School of Medicine, Keele University, Stoke-on-Trent, ST4 7QB, UK;(2) Birmingham and Midland Eye Centre, City Hospital, Birmingham, B18 7QU, UK |
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Abstract: | 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. |
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Keywords: | Instrumentation Stress relaxation Hysteresis Biomechanics |
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