Optimising The Biomechanics Of Crosslinked Porcine-Derived Corneal Lenticules For The Treatment Of Advanced Keratoconus

Corneal transplant is the main treatment for advanced keratoconus. However, transplantation has associated risks and there remains a worldwide shortage of human donor corneas. Recently, lenticular implants formed from decellularised and processed porcine corneal tissue (Xenia®, Gebauer Medizintechnik GmbH), have demonstrated efficacy in clinical trials. However, controlling lenticule properties is challenging due to variability in the baseline material. Further, implants more generally have associated complications due to a mismatch in their biomechanics relative to surrounding tissue. Here we use interferometry to quantify the mechanical properties of lenticules and correlate this with processing variables used to produce Xenia® implants.

All lenticular implants were produced by Gebauer Medizintechnik GmbH, Neuhausen, DE. Imaging was conducted by Abby Wilson at UCL Mechanical Engineering, London, UK.

Corneal lenticules (diameter = 9mm, thickness = 150µm) were extracted from the central anterior stroma of porcine corneas (< 24hrs post-mortem). 12 samples were not subjected to any further processing, the remaining 12 samples underwent a 4-stage proprietary processing procedure involving decellularisation, washing, compression and crosslinking. Thickness changes were recorded for all processed lenticules after compression. The lenticules were stored in sample tubes and immersed in trinity solution for shipment to the UK. Interferometry was used to quantify the stiffness of the lenticules in terms of Young’s modulus, through evaluating the deformation of the lenticules in response to physiologically representative pressure variations.

The stiffness of all processed lenticules was greater than the stiffness of lenticules that had not undergone processing (21.9 vs 10.9 MPa). Variability in the stiffness of the processed lenticules was 3-fold greater than variability in the stiffness of the unprocessed lenticules. This indicated variability in the response of the lenticules to the processing procedures used, which was corroborated by measured variability in the thickness of the lenticules after compression and prior to crosslinking.

Porcine derived lenticules offer a promising treatment for advanced Keratoconus. Due to the biological nature of the baseline material, and resulting variability in response to the processing methods used, further research is required to establish the relationship of individual processing parameters to the final lenticule stiffness. Ultimately facilitating the manufacturing and commercial supply of lenticules with predictable, customised and optimised properties.