Modeling the load resistance in laser-assisted cornea transplantation

In femtosecond laser assisted keratoplasty different surgical wound profiles can be performed, such as mushroom, zigzag, anvil, Christmas tree, etc. The cut shape is chosen by the surgeon on the basis of patient's morphology and pathology and on the gained experience. This work aims to qualitatively evaluate the biomechanical load resistance of the different configurations that are currently used in penetrating keratoplasty (PK), in order to support the surgeon's choice. A 2D and a 3D finite-element biomechanical model of the human cornea was developed and different geometric configurations for PK were designed. The internal pressure was raised until the wound misaligned; wound prolapse then occurred. As a result, we evidenced a different wound resistance to internal loads in the different laser trephined profiles. The anvil profile was more resistant to the increasing internal pressure than was the mushroom or the zig zag pattern. This result is in accordance with the clinical results observed in previously treated patients. 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.