Secrets of Corneal Stiffness: A New Map for Keratoconus Patients
Authors: Zhang, H., Eliasy, A., Lopes, B., Abass, A., Vinciguerra, R., Vinciguerra, P., Ambrósio Jr, R., Roberts, C.J., and Elsheikh, A.
Journal: Frontiers in Bioengineering and Biotechnology
Publication Date: Mar 2021
SSI maps for KC corneas with cones experiencing fibril reductions of 0 (A), 20% (B), 40% (C), and 60% (D). The cones had 2.0 mm radius and were located on the vertical central meridian of the cornea. In all cases, the cones’ centers were at 1.0 mm away from corneal apex. The values of SSI provided for each case represented the mean ± standard deviation and range from minimum to maximum value. (E,F) depict the SSI values along the horizontal central meridian of the cornea before (E) and after (F) normalization relative to the corresponding SSI values of the healthy cornea.
Summary:
Our eyes are the windows to the world, and the cornea plays a significant role in how we perceive it. In our recent study, we introduced a new method to map the mechanical stiffness of healthy and keratoconic corneas, a condition that affects the cornea's shape and vision. This new method, called the Stress-Strain Index (SSI) map, estimates the regional variation of biomechanical stiffness across the corneal surface.
Using numerical modelling based on the finite element method, we simulated healthy and keratoconic corneas and determined the regional variation of mechanical stiffness across the corneal surface. The SSI values varied slightly in healthy eyes, while keratoconic corneas showed substantial reductions in SSI values inside the cone. These reductions depended on the extent of the disease and increased with more significant simulated losses in fibril density in the cone area.
Our findings suggest that SSI maps can provide an estimation of the regional variation of biomechanical stiffness across the corneal surface. These maps could be particularly useful in keratoconic corneas, demonstrating the dependence of corneal biomechanical behaviour on the tissue's microstructure and offering a tool to fundamentally understand the mechanics of keratoconus progression in individual patients.
By developing these SSI maps, we can visualise the effect of the disease on the affected area and help improve our fundamental understanding of the mechanics of keratoconus progression in individual patients. In the future, these maps may lead to a better understanding and management of the disease.
Although our study has its limitations, such as the assumption that all healthy corneas have the same microstructure, it provides a starting point for further research and development. Our work has the potential to improve the understanding of corneal biomechanics and contribute to the development of better diagnostic and treatment tools for keratoconus patients.