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

Numerical results for the patient IV in the preoperative and postoperative case.(a) Steepest meridian and NT direction angle versus IOP. (b) Steepest meridian asphericity coefficient versus IOP. (c) Flattest meridian asphericity coefficient versus IOP.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0130426.g012: Numerical results for the patient IV in the preoperative and postoperative case.(a) Steepest meridian and NT direction angle versus IOP. (b) Steepest meridian asphericity coefficient versus IOP. (c) Flattest meridian asphericity coefficient versus IOP.

Mentions: The reprofiling of the cornea due to laser ablation modifies the geometry inducing a change in the best fitting biconic parameters. The variation of the biconic parameters with IOP are visualized in the Figs 11–12. Fig 11 shows, for Patient IV, the steepest and the flattest meridian curvatures versus the IOP for the preoperative and postoperative corneas, while Fig 12 shows the angle and the asphericity coefficients in the steepest and flattest meridian directions versus the IOP. Fig 13 shows the variation of the RP in the NT and SI direction with IOP in preoperative and postoperative cases for Patient III, treated for myopia, and Patient IV, treated for astigmatism.


Customized Finite Element Modelling of the Human Cornea.

Simonini I, Pandolfi A - PLoS ONE (2015)

Numerical results for the patient IV in the preoperative and postoperative case.(a) Steepest meridian and NT direction angle versus IOP. (b) Steepest meridian asphericity coefficient versus IOP. (c) Flattest meridian asphericity coefficient versus IOP.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0130426.g012: Numerical results for the patient IV in the preoperative and postoperative case.(a) Steepest meridian and NT direction angle versus IOP. (b) Steepest meridian asphericity coefficient versus IOP. (c) Flattest meridian asphericity coefficient versus IOP.
Mentions: The reprofiling of the cornea due to laser ablation modifies the geometry inducing a change in the best fitting biconic parameters. The variation of the biconic parameters with IOP are visualized in the Figs 11–12. Fig 11 shows, for Patient IV, the steepest and the flattest meridian curvatures versus the IOP for the preoperative and postoperative corneas, while Fig 12 shows the angle and the asphericity coefficients in the steepest and flattest meridian directions versus the IOP. Fig 13 shows the variation of the RP in the NT and SI direction with IOP in preoperative and postoperative cases for Patient III, treated for myopia, and Patient IV, treated for astigmatism.

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