Acoustic micro-tapping optical coherence elastography (AuT-OCE) to quantify biomechanical changes following corneal collagen crosslinking: Ex vivo study

In degenerative corneal diseases, such as keratoconus, local deterioration in mechanical properties results in corneal deformation and vision loss. Collagen cross-linking (CXL) has been used to delay progression of keratoconus with some success in slowing the disease, both long-term and immediate outcomes remain unpredictable for each patient. There is a clear unmet clinical need to develop a personalized biomechanical model based on quantitative maps of corneal mechanical moduli to quantify both biomechanical properties and predict final corneal shape. In this study, we use a novel non-contact, non-invasive AuT-OCE method to quantify corneal elasticity. Because of the anisotropic corneal property due to its collagen structure, a nearly incompressible transversely isotropic (NITI) model was developed to characterize its elasticity. It has been shown that in-plane tensile and out-of-plane shear properties are defined by different moduli, E and G, respectively. Both E and G experienced significantly different stiffening responses to CXL. The increase in G relative to E suggests that while CXL strengthened the tensile strength of the tissue, the ability of the cornea to resist shearing forces was more dramatically altered. AmT-OCE appears capable of changing diagnostic criteria of ectatic corneal diseases, leading to early diagnosis and more precise surgical planning.