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

Area of Science:

• Ophthalmology and Biomedical Engineering
• Biophysics and Material Science

Background:

• The human cornea exhibits anisotropic elastic properties, crucial for maintaining its structural integrity.
• Ultraviolet cross-linking (CXL) is a therapeutic procedure to strengthen the cornea, but its precise effects on anisotropic biomechanics require detailed evaluation.

Purpose of the Study:

• To quantify the changes in anisotropic elastic properties of ex vivo human cornea following ultraviolet cross-linking (CXL).
• To assess the efficacy of noncontact acoustic micro-tapping optical coherence elastography (AμT-OCE) in measuring these CXL-induced biomechanical alterations.

Main Methods:

• Ex vivo human donor corneas (n=22) were analyzed using noncontact AμT-OCE.
• Elastic properties, including in-plane Young's modulus (E) and out-of-plane shear modulus (G), were determined.
• A transverse isotropic model was employed for modulus reconstruction, with results validated by destructive mechanical testing.

Main Results:

• CXL treatment significantly increased both in-plane and out-of-plane elastic moduli of the human cornea.
• In a paired study (n=7), the in-plane Young's modulus increased from 19 MPa to 43 MPa.
• The out-of-plane shear modulus increased from 188 kPa to 673 kPa post-CXL, consistent with mechanical test validations.

Conclusions:

• Noncontact AμT-OCE is capable of evaluating anisotropic elastic properties in human corneas.
• The study demonstrates that AμT-OCE can effectively measure the significant biomechanical stiffening induced by ultraviolet CXL.
• These findings highlight the utility of AμT-OCE for monitoring CXL efficacy and understanding corneal biomechanics.