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Finite-element modeling of posterior lamellar keratoplasty: construction of theoretical nomograms for induced
Gagik P Djotyan1, H Kaz Soong, Shahzad Mian
1Center for Ultrafast Optical Science, University of Michigan College of Engineering, Ann Arbor, MI, USA.
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.