Limits...
Customized Finite Element Modelling of the Human Cornea.

Simonini I, Pandolfi A - PLoS ONE (2015)

Bottom Line: Corneal elevation maps of five human eyes were taken with a rotating Scheimpflug camera combined with a Placido disk before and after refractive surgery.Patient-specific solid models were created and discretized in finite elements to estimate the corneal strain and stress fields in preoperative and postoperative configurations and derive the refractive parameters of the cornea.Patient-specific models can be used as indicators of feasibility before performing the surgery.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Matematica, Politecnico di Milano, Milano, Italy.

ABSTRACT

Aim: To construct patient-specific solid models of human cornea from ocular topographer data, to increase the accuracy of the biomechanical and optical estimate of the changes in refractive power and stress caused by photorefractive keratectomy (PRK).

Method: Corneal elevation maps of five human eyes were taken with a rotating Scheimpflug camera combined with a Placido disk before and after refractive surgery. Patient-specific solid models were created and discretized in finite elements to estimate the corneal strain and stress fields in preoperative and postoperative configurations and derive the refractive parameters of the cornea.

Results: Patient-specific geometrical models of the cornea allow for the creation of personalized refractive maps at different levels of IOP. Thinned postoperative corneas show a higher stress gradient across the thickness and higher sensitivity of all geometrical and refractive parameters to the fluctuation of the IOP.

Conclusion: Patient-specific numerical models of the cornea can provide accurate quantitative information on the refractive properties of the cornea under different levels of IOP and describe the change of the stress state of the cornea due to refractive surgery (PRK). Patient-specific models can be used as indicators of feasibility before performing the surgery.

No MeSH data available.


Related in: MedlinePlus

Finite element discretization of a patient-specific model of a human cornea in the physiological configuration.(a) anterior surface view; (b) NT side view; and (c) NT section. The boundary conditions for static analysis include constrained displacement of the limbus nodes in the radial direction, while the allowed displacements at the limbus mimic the free rotation of the corneal shell about the central limbus circumference.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4476710&req=5

pone.0130426.g006: Finite element discretization of a patient-specific model of a human cornea in the physiological configuration.(a) anterior surface view; (b) NT side view; and (c) NT section. The boundary conditions for static analysis include constrained displacement of the limbus nodes in the radial direction, while the allowed displacements at the limbus mimic the free rotation of the corneal shell about the central limbus circumference.

Mentions: An existing parametrized mesh generator for the cornea [17, 20] has been adapted to deal with the customized solid model of the cornea. By using a two-dimensional grid generator, the code creates a mesh discretized in 8-node brick elements with linear displacement interpolation. The discretization parameters are the number of elements along the principal diameter and the number of elements across the thickness. An example of patient-specific mesh is shown in Fig 6, and consists of 2500 nodes and 1728 brick elements, with three layers of elements across the thickness. The mesh generator uses a new algorithm based on Green functions [38] to interpolate the cloud of points with a continuous surface of equation


Customized Finite Element Modelling of the Human Cornea.

Simonini I, Pandolfi A - PLoS ONE (2015)

Finite element discretization of a patient-specific model of a human cornea in the physiological configuration.(a) anterior surface view; (b) NT side view; and (c) NT section. The boundary conditions for static analysis include constrained displacement of the limbus nodes in the radial direction, while the allowed displacements at the limbus mimic the free rotation of the corneal shell about the central limbus circumference.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4476710&req=5

pone.0130426.g006: Finite element discretization of a patient-specific model of a human cornea in the physiological configuration.(a) anterior surface view; (b) NT side view; and (c) NT section. The boundary conditions for static analysis include constrained displacement of the limbus nodes in the radial direction, while the allowed displacements at the limbus mimic the free rotation of the corneal shell about the central limbus circumference.
Mentions: An existing parametrized mesh generator for the cornea [17, 20] has been adapted to deal with the customized solid model of the cornea. By using a two-dimensional grid generator, the code creates a mesh discretized in 8-node brick elements with linear displacement interpolation. The discretization parameters are the number of elements along the principal diameter and the number of elements across the thickness. An example of patient-specific mesh is shown in Fig 6, and consists of 2500 nodes and 1728 brick elements, with three layers of elements across the thickness. The mesh generator uses a new algorithm based on Green functions [38] to interpolate the cloud of points with a continuous surface of equation

Bottom Line: Corneal elevation maps of five human eyes were taken with a rotating Scheimpflug camera combined with a Placido disk before and after refractive surgery.Patient-specific solid models were created and discretized in finite elements to estimate the corneal strain and stress fields in preoperative and postoperative configurations and derive the refractive parameters of the cornea.Patient-specific models can be used as indicators of feasibility before performing the surgery.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento di Matematica, Politecnico di Milano, Milano, Italy.

ABSTRACT

Aim: To construct patient-specific solid models of human cornea from ocular topographer data, to increase the accuracy of the biomechanical and optical estimate of the changes in refractive power and stress caused by photorefractive keratectomy (PRK).

Method: Corneal elevation maps of five human eyes were taken with a rotating Scheimpflug camera combined with a Placido disk before and after refractive surgery. Patient-specific solid models were created and discretized in finite elements to estimate the corneal strain and stress fields in preoperative and postoperative configurations and derive the refractive parameters of the cornea.

Results: Patient-specific geometrical models of the cornea allow for the creation of personalized refractive maps at different levels of IOP. Thinned postoperative corneas show a higher stress gradient across the thickness and higher sensitivity of all geometrical and refractive parameters to the fluctuation of the IOP.

Conclusion: Patient-specific numerical models of the cornea can provide accurate quantitative information on the refractive properties of the cornea under different levels of IOP and describe the change of the stress state of the cornea due to refractive surgery (PRK). Patient-specific models can be used as indicators of feasibility before performing the surgery.

No MeSH data available.


Related in: MedlinePlus