Possible depth-resolved reconstruction of shear moduli in the cornea following collagen crosslinking (CXL) with optical coherence tomography and elastography

TL;DR

This study combines OCT and elastography techniques to non-invasively reconstruct depth-dependent shear moduli in corneas post-CXL, providing insights into the localized effects of collagen crosslinking on corneal stiffness.

Contribution

It introduces a novel method integrating phase-decorrelation OCT and acoustic micro-tapping elastography for depth-resolved corneal stiffness assessment after CXL.

Findings

CXL penetration depth varies from 100μm to 150μm across the cornea

A two-layer model effectively quantifies localized stiffness changes

Reconstructed elastic moduli reflect overall corneal mechanical properties

Abstract

Collagen crosslinking of the cornea (CXL) is commonly employed to prevent or treat keratoconus. Although the change of corneal stiffness induced by CXL surgery can be monitored with non-contact dynamic Optical Coherence Elastography (OCE) by tracking mechanical wave propagation, the depth dependence of this change is still unclear if the cornea is not crosslinked through the whole depth. Here we propose to combine phase-decorrelation measurement applied to OCT structural images and acoustic micro-tapping (A$\mu$T) OCE to explore possible depth reconstruction of stiffness within crosslinked corneas in an ex vivo human cornea sample. The analysis of experimental OCT images is used to define the penetration depth of CXL into the cornea, which varies from $\sim$100$\mu m$ in the periphery to $\sim$150$\mu m$ in the central area and exhibits a sharp transition between areas. This information was used in a two-layer analytical model to quantify the stiffness of the treated layer. We also discuss how the elastic moduli of partially CXL-treated cornea layers reconstructed from OCE measurements reflect the effective mechanical stiffness of the entire cornea to properly quantify surgical outcome.