Non-contact acoustic micro-tapping optical coherence elastography for evaluating biomechanical changes in the cornea following UV/riboflavin collagen cross linking: ex vivo human study
Purpose: To evaluate changes in the anisotropic elastic properties of ex vivo human cornea treated with UV cross-linking (CXL) using non-contact acoustic micro-tapping Optical Coherence Elastography (AuT-OCE) Design: AuT performed on normal and CXL ex vivo human donor cornea Methods: Elastic properties of normal and UV CXL treated human corneas were quantified using non-contact acoustic micro-tapping Optical Coherence Elastography (AuT-OCE) Main Outcome Measures: Corneal elastic moduli (in-plane Young's, E, and out-of-plane shear, G) can be evaluated in both normal and CXL treated tissues, as well as during the CXL procedure using non-contact AuT-OCE. Results: CXL induced a significant increase in both the tensile and shear moduli in human cornea. The mean in the paired study (pre- and post-, n=7) of the in-plane Young's modulus, E=3u, increased from 19 MPa to 43 MPa while the out-of-plane shear modulus, G, increased from 188 kPa to 673 kPa. Mechanical tests in a subgroup support CXL-induced cornea moduli changes and generally agree with AuT-OCE. Conclusions: The human cornea is a highly anisotropic material where in-plane mechanical properties are very different from those out-of-plane. Non-contact AuT-OCE can measure changes in the anisotropic elastic properties in human cornea as a result of UV-CXL.