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TECHNICAL PAPERS: Soft Tissue

Biomechanical Modeling of Refractive Corneal Surgery

[+] Author and Article Information
V. Alastrué, B. Calvo, E. Peña, M. Doblaré

Group of Structural Mechanics and Material Modelling, Aragon Institute of Engineering Research (I3A),  University of Zaragoza, Spain

J Biomech Eng 128(1), 150-160 (Aug 23, 2005) (11 pages) doi:10.1115/1.2132368 History: Received January 10, 2005; Revised August 23, 2005

The aim of refractive corneal surgery is to modify the curvature of the cornea to improve its dioptric properties. With that goal, the surgeon has to define the appropriate values of the surgical parameters in order to get the best clinical results, i.e., laser and geometric parameters such as depth and location of the incision, for each specific patient. A biomechanical study before surgery is therefore very convenient to assess quantitatively the effect of each parameter on the optical outcome. A mechanical model of the human cornea is here proposed and implemented under a finite element context to simulate the effects of some usual surgical procedures, such as photorefractive keratectomy (PRK), and limbal relaxing incisions (LRI). This model considers a nonlinear anisotropic hyperelastic behavior of the cornea that strongly depends on the physiological collagen fibril distribution. We evaluate the effect of the incision variables on the change of curvature of the cornea to correct myopia and astigmatism. The obtained results provided reasonable and useful information in the procedures analyzed. We can conclude from those results that this model reasonably approximates the corneal response to increasing pressure. We also show that tonometry measures of the IOP, underpredicts its actual value after PRK or LASIK surgery.

FIGURES IN THIS ARTICLE
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Copyright © 2006 by American Society of Mechanical Engineers
Topics: Surgery , Cornea
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References

Figures

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Figure 1

Pressure-displacement curves from numerical fits and experimental data corresponding to the membrane inflating test

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Figure 2

Geometrical parameters and finite element mesh of the human cornea

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Figure 3

Fibril distribution in the finite element model of the human cornea

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Figure 4

Ablation parameters and finite element model of the PRK surgery model for D=10(32)

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Figure 5

Effect of acute on collagen fibril stiffness in PRK surgery

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Figure 6

Model of the arcuate keratotomy

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Figure 7

Effect of incisions on collagen fibril stiffness in LRI surgery

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Figure 8

Results in the healthy human cornea

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Figure 9

Vertical displacement after PRK surgery (mm)

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Figure 10

Deformed configuration with arcuate incisions with α=90°

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Figure 11

Vertical displacement after LRI surgery (mm)

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