A study of piezoelectric and mechanical anisotropies of the human cornea

Jayasuriya, Ambalangodage C.; Ghosh, Snehasish; Scheinbeim, J. I.; Lubkin, Virginia; Bennett, G.; Kramer, P.

doi:10.1016/s0956-5663(02)00144-6

Cited by 72 publications

(53 citation statements)

References 18 publications

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“…279 This decrease has generally been attributed to the uptake of intrafibrillar water. However, piezoelectricity in other collagenous tissues (e.g., cornea and sclera) has been shown to increase with increasing water content, [280][281][282] highlighting existing discrepancies in the literature between results obtained using macroscale measurements. In this context, locally probing the electromechanical properties of these complex biosystems allows such discrepancies to be resolved by determining the geometrical orientation of the response at the scale of the elements responsible for the piezoelectric behaviour.…”

Section: Electromechanical Phenomena In Organic and Biological Systemsmentioning

confidence: 97%

Applications of piezoresponse force microscopy in materials research: from inorganic ferroelectrics to biopiezoelectrics and beyond

Denning

Guyonnet

Rodriguez

2016

International Materials Reviews

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Piezoresponse force microscopy (PFM) probes the mechanical deformation of a sample in response to an electric field applied with the tip of an atomic force microscope. Originally developed more than two decades ago to study ferroelectric materials, this technique has since been used to probe electromechanical functionality in a wide range of piezoelectric materials including organic and biological systems. PFM has also been demonstrated as a useful tool to detect mechanical strain originating from electrical phenomena in nonpiezoelectric materials. Paralleling advances in analytical and numerical modelling, many technical improvements have been made in the last decade: switching spectroscopy PFM allows the polarisation switching properties of ferroelectrics to be resolved in real space with nanometric resolution, while dual ac resonance tracking and band excitation PFM have been used to improve the signal-to-noise ratio. In turn, these advances have led to increasingly large multidimensional data sets containing more complete information on the properties of the sample studied. In this review, PFM operation and calibration are described, and recent advances in the characterisation of electromechanical coupling using PFM are presented. The breadth of the systems covered highlights the versatility and wide applicability of PFM in fields as diverse as materials engineering and nanomedicine. In each of these fields, combining PFM with complementary techniques is key to develop future insight into the intrinsic properties of the materials as well as for device applications.

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Section: Electromechanical Phenomena In Organic and Biological Systemsmentioning

confidence: 97%

Applications of piezoresponse force microscopy in materials research: from inorganic ferroelectrics to biopiezoelectrics and beyond

Denning

Guyonnet

Rodriguez

2016

International Materials Reviews

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“…Unfortunately, reported values of YM for a given tissue can span several orders of magnitude. The human cornea is a good example, with reported modulus values ranging from 2.9 kPa 36 to 19 MPa 37 when measured by atomic force microscopy (AFM) 38 tensile stretching, 39,40 tonometry, [41][42][43] or inflation/bulge testing, 36,37,[44][45][46][47] This wide variation in reported YM values is not limited to the cornea. Part of the variation in reported YM values stems from variation in controllable experimental variables.…”

Section: Introductionmentioning

confidence: 99%

Indentation Versus Tensile Measurements of Young's Modulus for Soft Biological Tissues

McKee

Russell

Murphy³

2011

Tissue Engineering Part B: Reviews

579

402

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“…Measurements of the modulus of sclera along the radial direction were carried out by Battaglioli and Kamm [19], who found radial values of modulus lower than the circumferential values by a factor of up to 100. Anisotropy in the cornea has also been established Jayasuriya et al [3]. There is a clear need to allow for anisotropic material behaviour for both the cornea and sclera.…”

Section: Materials Propertiesmentioning

confidence: 93%

“…The principal function of the cornea is optical since it is thought to be responsible for as much as 70.0% of the total refractive power of the eye due to its transparency; however its mechanical properties also make it capable of resisting the intraocular pressure and providing a protective coat for the eye. The cornea's protective qualities are attributed to the collagen fibres within this organ [2], which are in turn associated with its known anisotropic nature [3]. The thickness of the cornea varies across it, the thinnest region being located at the centre with a typical value of 0.52 mm.…”

Section: Introductionmentioning

confidence: 99%

On the Validity of the Imbert-Fick Law: Mathematical Modelling of Eye Pressure Measurement

Castro¹,

Fitt²,

Sweeney³

2016

WJM

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Ophthalmologists rely on a device known as the Goldmann applanation tonometer to make intraocular pressure (IOP) measurements. It measures the force required to press a flat disc against the cornea to produce a flattened circular region of known area. The IOP is deduced from this force using the Imbert-Fick principle. However, there is scant analytical justification for this analysis. We present a mathematical model of tonometry to investigate the relationship between the pressure derived by tonometry and the IOP. An elementary equilibrium analysis suggests that there is no physical basis for traditional tonometric analysis. Tonometry is modelled using a hollow spherical shell of solid material enclosing an elastic liquid core, with the shell in tension and the core under pressure. The shell is pressed against a rigid flat plane. The solution is found using finite element analysis. The shell material is anisotropic. Values for its elastic constants are obtained from literature except where data are unavailable, when reasonable limits are explored. The results show that the force measured by the Goldmann tonometer depends on the elastic constant values. The relationship between the IOP and the tonometer readings is complex, showing potentially high levels of inaccuracy that depend on IOP.

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A study of piezoelectric and mechanical anisotropies of the human cornea

Cited by 72 publications

References 18 publications

Applications of piezoresponse force microscopy in materials research: from inorganic ferroelectrics to biopiezoelectrics and beyond

Applications of piezoresponse force microscopy in materials research: from inorganic ferroelectrics to biopiezoelectrics and beyond

Indentation Versus Tensile Measurements of Young's Modulus for Soft Biological Tissues

On the Validity of the Imbert-Fick Law: Mathematical Modelling of Eye Pressure Measurement

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