Debate regarding the mechanisms of how the eye changes focus (accommodation) and why this ability is lost with age (presbyopia) has recently been rejoined due to the advent of surgical procedures for the correction of presbyopia. Due to inherent confounding factors in both in vivo and in vitro measurement techniques, mechanical modeling of the behavior of the ocular lens in accommodation has been attempted to settle the debate. However, a paucity of reliable mechanical property measurements has proven problematic in the development of a successful mechanical model of accommodation. Instrumented microindentation was utilized to directly measure the local elastic modulus and dynamic response at various locations in the lens. The young porcine lens exhibits a large modulus gradient with the highest modulus appearing at the center of the nucleus and exponentially decreasing with distance. The loss tangent was significantly higher in the decapsulated lens and the force waveform amplitude decreased significantly upon removal of the lens capsule. The findings indicate that localized measurements of the lens’ mechanical properties are necessary to achieve accurate quantitative parameters suitable for mechanical modeling efforts. The results also indicate that the lens behaves as a crosslinked gel rather than as a collection of individual arched fiber cells.
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April 2009
Technical Briefs
Microindentation of the Young Porcine Ocular Lens
Matthew Reilly,
Matthew Reilly
Researcher
Department of Veterans Affairs
, 915 North Grand Boulevard, St. Louis, MO 63106; Department of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis
, St. Louis, MO 63110
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Nathan Ravi
e-mail: nathan.ravi@med.va.gov
Nathan Ravi
Chief of Staff
Department of Veterans Affairs
, 915 North Grand Boulevard, St. Louis, MO 63106; Department of Energy, Environmental, and Chemical Engineering, and Department of Ophthalmology and Visual Sciences, Washington University in St. Louis
, St. Louis, MO 63110
Search for other works by this author on:
Matthew Reilly
Researcher
Department of Veterans Affairs
, 915 North Grand Boulevard, St. Louis, MO 63106; Department of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis
, St. Louis, MO 63110
Nathan Ravi
Chief of Staff
Department of Veterans Affairs
, 915 North Grand Boulevard, St. Louis, MO 63106; Department of Energy, Environmental, and Chemical Engineering, and Department of Ophthalmology and Visual Sciences, Washington University in St. Louis
, St. Louis, MO 63110e-mail: nathan.ravi@med.va.gov
J Biomech Eng. Apr 2009, 131(4): 044502 (4 pages)
Published Online: January 30, 2009
Article history
Received:
May 22, 2008
Revised:
October 10, 2008
Published:
January 30, 2009
Citation
Reilly, M., and Ravi, N. (January 30, 2009). "Microindentation of the Young Porcine Ocular Lens." ASME. J Biomech Eng. April 2009; 131(4): 044502. https://doi.org/10.1115/1.3072891
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