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

• Published in: Ophthalmology science (Online) Vol. 3; no. 2; p. 100257
• Main Authors: Kirby, Mitchell A, Pelivanov, Ivan, Regnault, Gabriel, Pitre, John J, Wallace, Ryan T, O'Donnell, Matthew, Wang, Ruikang K, Shen, Tueng T
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier 01-06-2023
• Subjects: Original; Cornea; Elastic Anisotropy; IOP, intraocular pressure; NITI model; UV, ultraviolet; Optical Coherence Elastography; BSS, balanced saline solution; OCE, optical coherence elastography; CXL, cross-linking; NITI, nearly incompressible transverse isotropy; RF, riboflavin; Cross-linking; AμT, acoustic micro-tapping
• ISSN: 2666-9145
• DOI: 10.1016/j.xops.2022.100257

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 (AμT-OCE).
Acoustic micro-tapping OCE was performed on normal and CXL human donor cornea in an ex vivo laboratory study.
Normal human donor cornea (n = 22) divided into 4 subgroups. All samples were stored in optisol.
Elastic properties (in-plane Young's,
, and out-of-plane,
, shear modulus) of normal and ultraviolet CXL-treated human corneas were quantified using noncontact AμT-OCE. A nearly incompressible transverse isotropic model was used to reconstruct moduli from AμT-OCE data. Independently, cornea elastic moduli were also measured with destructive mechanical tests (tensile extensometry and shear rheometry).
Corneal elastic moduli (in-plane Young's modulus,
, in-plane, μ, and out-of-plane,
, shear moduli) can be evaluated in both normal and CXL treated tissues, as well as monitored during the CXL procedure using noncontact AμT-OCE.
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,
, increased from 19 MPa to 43 MPa, while the out-of-plane shear modulus,
increased from 188 kPa to 673 kPa. Mechanical tests in a separate subgroup support CXL-induced cornea moduli changes and generally agree with noncontact AμT-OCE measurements.
The human cornea is a highly anisotropic material where in-plane mechanical properties are very different from those out-of-plane. Noncontact AμT-OCE can measure changes in the anisotropic elastic properties in human cornea as a result of ultraviolet CXL.