Biomechanical FEM model of the cornea in femtosecond laser assisted keratoplasty

Femtosecond laser is routinely used in Ophthalmology to cut donor and patient's cornea in lamellar or penetrating keratoplasty. Different cut shapes can be chosen, on the basis of the specific patient's pathology and morphology and on surgeon's skills. Different cut geometries provide different internal load resistance of the cornea, and this can affect the surgical outcomes. This work aims to qualitatively evaluate the biomechanical load resistance of the different configurations that are currently used in laser assisted keratoplasty, in order to support the surgeon's choice. A 3D finiteelement biomechanical model of the human cornea was developed and different geometric configurations were designed, taking into account the possible different orientations of the cornea lamellae. We evidenced a different wound resistance to internal loads in the different laser trephined profiles, as well as a different distribution of the stresses in relation to the donor cornea orientation. The analyzed profiles are the mushroom, top hat and anvil. The anvil profile resulted more resistant to the increasing internal pressure, in accordance with the clinical results. The anvil profile enabled the apposition of a restricted number of sutures and early suture removal, thanks to its greater mechanical load resistance. These advantages can contribute to a faster visual recovery in patients undergoing penetrating keratoplasty.