Finite-element modeling of posterior lamellar keratoplasty: construction of theoretical nomograms for induced refractive errors.

PURPOSE

To estimate the theoretical corneal refractive error induced by mechanical weakening effects from posterior lamellar keratoplasty (PLKP) in the human cornea.

METHODS

The refractive effects of PLKP are simulated by finite-element modeling (FEM) as a mathematical function of the thickness of the excised posterior lamellar corneal button, with a nonlinear formulation of stress-strain relation for the corneal material. A theoretical nomogram was developed to correlate the refractive changes to button thickness.

RESULTS

The predicted refractive change after PLKP is less than 1 dpt for a 170-microm thickness posterior corneal button over a broad range of Young's modulus. Thicker buttons result in greater surgically induced refractive errors.

CONCLUSIONS

According to FEM analysis, the excision of a posterior lamellar button of less than 170 microm thickness produces a minimal predicted refractive change (< 1 dpt) in the cornea after PLKP.