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Finite element analysis of corneal biomechanics during photorefractive keratectomy

Poster Details

First Author: K.Moutsouris GREECE

Co Author(s):    P. Sanchez   A. Pandolfi           

Abstract Details



Purpose:

Numerical investigation on the biomechanical and optical behavior of human corneas under physiological conditions and quantitative estimate of the changes in refractive power (RP) and in stress due to myopic compound photo-refractive keratectomy

Setting:

Athineum Refractive Center, Athens, Greece and Politecnico di Milano, Italy

Methods:

Corneal topographies of ten human eyes of five patients were taken with Orbscan topographer before and after laser refractive corneal surgery. Ten patient specific numerical models of the corneas were created and discretized into finite elements, in order to estimate the strain and stress fields in the cornea due to the action of the intraocular pressure (IOP) in preoperative and postoperative configurations. The biomechanical response in the postoperative eyes have been computed in two different ways. First, by modeling directly the postoperative geometry provided by the topographer. Second, by reproducing the cornea ablation planned in the refractive surgery with a numerical reprofiling procedure implemented in the code.

Results:

The biomechanical response of the postoperative corneas is more compliant than the one of preoperative cornea. Within the optical zone, the thinned corneal thickness reduces the mechanical stiffness, causes local re-steepening, and makes the RP more sensitive to the variation of the IOP. At the physiological IOP (≈16 mmHg), with respect to preoperative corneas postoperative corneas show an average 7% forward increase in the apical displacement and an average 20% increase in the stress components at the center of the anterior surface.

Conclusions:

Patient specific numerical models of the cornea can provide accurate quantitative information on the changes in RP and in stress distribution due to refractive surgery and can be used as reliable predictive tools before performing the actual surgery. FINANCIAL INTEREST: NONE

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