Finite Element Modeling of Cornea for Penetrating Keratoplasty: Development of a New Wound Geometry

Abstract

Cornea transplant surgery, also known as Keratoplasty, is a procedure in which a part of a patient’s cornea is replaced with corneal tissue from a healthy donor eye obtained from an eye bank. The cornea being replaced is referred to as the host while the donor cornea is referred to as the graft. Presently, the procedure utilizes 16 to 24 interrupted sutures in a radial pattern to ensure the graft-host wound closure post operation. Suture placement needs to be performed with a high level of skill, ensuring all sutures are near identical in their pass length, depth, tension, distance from the optical center of the cornea and radiality. Problems with any of the mentioned factors could result in the induction of astigmatism, requiring multiple post-operative visits – usually over the course of a year – to assess and mitigate it. The procedure in itself is time intensive, taking between 45 and 75 minutes for a full transplant by an experienced surgeon. Therefore, the cornea transplant surgeon needs a method of graft-host wound closure that changes the way current sutures are used or the way their forces are distributed, minimizes the number of sutures used in the current manner, and/or abandons sutures in lieu of another technology because sutures as used in the current manner create astigmatism that is difficult to manage (for the reasons listed above, and probably others). Finite Element Analysis was used to predict the behavior of the cornea under different loading conditions. One of the solutions proposed in this work attempt to limit the number of sutures required to a maximum of 12 by utilizing stopping forces created due to the geometry of the graft-host wound interface that minimize the separation of the graft from the host under the influence of intra-ocular pressure. The other solution is the introduction of an intra-stromal corneal ring segment which enables suturing force to be taken by the ring rather than the central cornea leading to less central cornea distortion.