Depth-resolved reconstruction of anisotropic elastic moduli in a crosslinked cornea with wave-based optical coherence elastography

Abstract

Ectatic changes in the cornea are typically marked by corneal thinning with increased corneal deformation and curvature, often leading to high levels of myopia and irregular astigmatism. The most common form of ectasia is keratoconus. Corneal collagen crosslinking (CXL) is commonly used to prevent or treat keratoconus. Limited penetration of CXL into the cornea may lead to a demarcation between treated and untreated regions, suggesting a two-layer structure after the treatment. Although corneal topography can be used to monitor corneal curvature changes pre- and post-surgery, it cannot predict surgical outcomes without mapping corneal elasticity. Recent studies in non-contact dynamic optical coherence elastography (OCE) demonstrated promise in quantifying changes in corneal anisotropic stiffness induced by CXL. However, depth dependent reconstruction of corneal elastic moduli following CXL remains challenging. Here, we show that the thickness of the crosslinked corneal layer can be determined from structural OCT, whereas its mechanical moduli can be reconstructed from acoustic micro-tapping (AuT) OCE using an analytical two-layer model of guided wave propagation. In addition, we discuss how the elastic moduli of partially CXL-treated cornea layers reflect the effective engineering stiffness of the entire cornea to properly quantify corneal deformation.