Acoustic Micro-Tapping Optical Coherence Elastography to Quantify Corneal Collagen Cross-Linking An Ex Vivo Human Study

Purpose: To evaluate changes in the anisotropic elastic properties of ex vivo human cornea treated with ultraviolet cross-linking (CXL) using noncontact acoustic micro-tapping optical coherence elastography (A & mu;T-OCE).Design: Acoustic micro-tapping OCE was performed on normal and CXL human donor cornea in an ex vivo laboratory study.Subjects: Normal human donor cornea (n = 22) divided into 4 subgroups. All samples were stored in optisol.Methods: Elastic properties (in-plane Young's, E, and out-of-plane, G, shear modulus) of normal and ultraviolet CXL-treated human corneas were quantified using noncontact A & mu;T-OCE. A nearly incompressible transverse isotropic model was used to reconstruct moduli from A & mu;T-OCE data. Independently, cornea elastic moduli were also measured with destructive mechanical tests (tensile extensometry and shear rheometry).Main Outcome Measures: Corneal elastic moduli (in-plane Young's modulus, E, in-plane, & mu;, and out-of -plane, G, shear moduli) can be evaluated in both normal and CXL treated tissues, as well as monitored during the CXL procedure using noncontact A & mu;T-OCE. Results: Cross-linking induced a significant increase in both in-plane and out-of-plane elastic moduli in human cornea. The statistical mean in the paired study (presurgery and postsurgery, n = 7) of the in-plane Young's modulus, E = 3m, 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 separate subgroup support CXL-induced cornea moduli changes and generally agree with noncontact A & mu;T-OCE measurements.Conclusions: The human cornea is a highly anisotropic material where in-plane mechanical properties are very different from those out-of-plane. Noncontact A & mu;T-OCE can measure changes in the anisotropic elastic properties in human cornea as a result of ultraviolet CXL. Financial Disclosure(s): Proprietary or commercial disclosure may be found after the references.& COPY; 2022 by the American Academy of Ophthalmology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).