Purchase this article with an account.
Ali Vahdati, William J Dupps; A fiber-reinforced porohyperelastic swelling model for mechanical behavior of cornea: Application to prediction of keratoconus initiation. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2040.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
It is known that cornea is a multi-phasic material composed of mainly interstitial fluid, proteoglycans and a highly organized network of collagen fibers. Our aim was to develop a computational model for representing the mechanical behavior of cornea including the effect of swelling and crimping of collagen fiber and apply this model to prediction of initiation of keratoconus.
A three-dimensional model of cornea and sclera was developed. Cornea was modeled as an anisotropic porohyperelastic swelling material. Collagen fibrils were modeled as three-dimensional springs and the effect of fibril splay was included. The interstitial fluid, hydrostatic and swelling pressure were also included in the study. Predictive capability of the model was tested for simulation of keratoconus formation in response to focal reduction in (1) ground matrix stiffness, (2) collagen fibrils stiffness, (3) proteoglycan fixed charge density and (4) organization of collagen fibrils.
First cornea was subjected to intraocular pressure loading until equilibrium was reached. By testing reductions in stiffness of each and combinations of various constituents of the model, it was found that keratoconus-like features developed when the matrix was weakened in combination with disorganization of collagen fibers. This combination of factors resulted in cone formation accompanied by thinning of cornea at the site of weakening. As a representative case and for a region of weakening with radius of 2 mm, 40 % weakening the corneal isotropic ground matrix combined with lack of preferred collagen fibril orientation resulted in 18% thinning of cornea at the apex of the cone.
<br /> The results of the study show that by combining a microstructurally-based model of collagen fibrils with a porohyperelastic swelling model, the main features of keratoconus initiation due to a cone-forming deformation can be predicted in accordance with a biomechanical common-final-pathway hypothesis of ectasia. The modeling approach utilized here further allowed for compartmentalization of mechanical loads between the interstitial fluid and multi-component solid matrix of cornea. The model’s capabilities will be further tested for prediction of corneal deformations in response to perturbation of mechanical properties post-refractive surgery.
This PDF is available to Subscribers Only