In Silico Characterization Of The Interaction Of Corneal Tissue With A Nitinol Intracorneal Implant For Keratoconus Correction

The GROSSO Reshaper is a nitinol dome-shaped device indicated for remodeling the keratoconic cornea and improving visual acuity. The device is implanted with a minimally invasive surgical procedure inside a corneal pocket created using a femto-laser. Its safety and reshaping effect were verified on 12 New Zealand rabbits and are currently under investigation in human patients. The surgical procedure and outcomes were simulated via the finite element method by digitally modelling the human cornea and device and virtually implanting it in a corneal pocket. This simulation enables the investigation of the biomechanical effect induced by the device on the corneal tissue, their interaction, and the assessment of the corneal remodeling effect.

PoliToBIOMed Lab, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Torino, Italy.

Universidad de Zaragoza, Zaragoza, Spain.

Biomedical and Clinical Sciences, Linköping University.

Recornea srl, Trieste, Italy.

FINANCIAL DISCLOSURE: This activity is part of the project HUMANeye which has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 878719. 

The 3D models of the human cornea based on literature data and the GROSSO Reshaper were reconstructed using Rhinoceros 3D. A numerical simulation of the surgical procedure was performed in Abaqus, implementing a hyperelastic constitutive model for the corneal tissue and a superelastic constitutive model for the device. A zero-pressure algorithm was used to determine the stress-free configuration of the cornea, i.e. excluding the effect of the intraocular pressure. The model was then repressurised and the implant placed within an intracorneal pocket. Finally, maximum principal stress and strain values were measured, and pre- and post-implantation keratometric parameters were compared to assess the biomechanical effects of the device.

In the repressurized model of the cornea, the implantation of the device within the intracorneal pocket produced Maximum Principal Stress and Maximum Principal Strain equal to 0.03 MPa and 3%, respectively, in correspondence of the corneal area in contact with the apical region of the device. The Kmean, defined as the average of the K1 (flattest meridian) and K2 (steepest meridian) values, was determined to be 43.37D prior to insertion of the device into the intracorneal pocket, and 43.72D post-insertion.

The developed digital twin demonstrates that the device supports the corneal tissue without inducing critical levels of stress or deformation. The value of Kmean showed minimal changes after the implantation of the GROSSO Reshaper, indicating that the device follows and preserves the natural curvature of the human cornea. The developed tool is able to evaluate the interaction between the device and corneal tissue, aiding the pre-surgical evaluation of the implant and the performance assessment of different device designs. Validation of the numerical results will be pursued using experimental data from the rabbit study and the ongoing first-patient study.