Simultaneous tensile and shear measurement of the human cornea in vivo using S0- and A0-wave optical coherence elastography

TL;DR

This paper introduces a novel optical coherence elastography method that simultaneously measures tensile and shear properties of the human cornea in vivo, aiding in clinical assessment of corneal biomechanics.

Contribution

The study develops a guided-wave elastography technique that excites and analyzes symmetric and anti-symmetric elastic waves to extract corneal tensile and shear moduli in vivo.

Findings

Measured in vivo tensile modulus of 3.6 MPa in humans.

Measured in vivo shear modulus of 76 kPa in humans.

Technique verified with phantoms and ex vivo corneas.

Abstract

Understanding corneal stiffness is valuable for improving refractive surgery, detecting corneal abnormalities, and assessing intraocular pressure. However, accurately measuring the elastic properties, particularly the tensile and shear moduli that govern mechanical deformation, has been challenging. To tackle this issue, we have developed guided-wave optical coherence elastography that can simultaneously excite and analyze symmetric (S0) and anti-symmetric (A0) elastic waves in the cornea at frequencies around 10 kHz and allows us to extract tensile and shear properties from measured wave dispersion curves. By applying acoustoelastic theory that incorporates corneal tension and a nonlinear constitutive tissue model, we verified the technique using elastomer phantoms and ex vivo porcine corneas and investigated the dependence on intraocular pressure. For two healthy human subjects, we measured a mean tensile modulus of 3.6 MPa and a mean shear modulus of 76 kPa in vivo with estimated errors of < 4%. This technique shows promise for the quantitative biomechanical assessment of the cornea in a clinical setting.