Exploring the Biomechanical Properties of the Human Cornea In Vivo Based on Corvis ST

Abstract

Purpose: The aim of this study was to provide a method to determine corneal nonlinear viscoelastic properties based on the output data of corneal visualization Scheimpflug technology (Corvis ST).Methods: The Corvis ST data from 18 eyes of 12 healthy humans were collected. Based on the air-puff pressure and the corneal displacement from the Corvis ST test of normal human eyes, the work done by the air-puff attaining the whole corneal displacement was obtained. By applying a visco-hyperelastic strain energy density function of the cornea, in which the first-order Prony relaxation function and the first-order Ogden strain energy were employed, the corneal strain energy during the Corvis ST test was calculated. Then the work done by the air-puff attaining the whole corneal displacement was completely regarded as the strain energy of the cornea. The identification of the nonlinear viscoelastic parameters was carried out by optimizing the sum of difference squares of the work and the strain energy using the genetic algorithm.Results: The visco-hyperelastic model gave a good fit to the data of corneal strain energy with time during the Corvis ST test (R2 > 0.95). The determined Ogden model parameter μ ranged from 0.42 to 0.74 MPa, and α ranged from 32.76 to 55.63. The parameters A and τ in the first-order Prony function were 0.09–0.36 and 1.21–1.95 ms, respectively.Conclusion: It is feasible to determine the corneal nonlinear viscoelastic properties based on the corneal contour information and air-puff pressure of the Corvis ST test.

In Vivo Corneal Biomechanical Properties in a Selected Chinese Population, Measured Using the Corneal Visualization Scheimpflug Technology

“…A video clip containing 140 digital frames corresponded to a recording time of 33 msec. The details of measurements on the Corvis ST are described elsewhere ( Robert et al, 2019 ; Zhang et al, 2021a ). In the latest release of the software, more DCR parameters [MIR, DARM (1 mm), DARM (2 mm) PS, ARtH, IR, SP-A1, and CBI) were introduced, together with bIOP.…”

Differences of Corneal Biomechanics Among Thin Normal Cornea, Forme-Fruste Keratoconus, and Cornea After SMILE

“…However, if we aim to know the characteristics of corneal biomechanical properties of each group, we need to further analysis biomechanical parameters, such as, elastic modulus and nonlinear elasticity, based on the relationship between DCR parameters and corneal biomechanical properties (not established yet) or the established mechanical models using the data output by Corvis ST (Boszczyk et al, 2017;Jannesari et al, 2019;Qin et al, 2019;Zhang et al, 2021), or direct measuring by optical correlation elastic imaging (Singh et al, 2018;Zhou et al, 2019;De Stefano et al, 2020;Chong and Dupps, 2021;Lan et al, 2021), Brillouin microscopy (Yun and Chernyak, 2018;Shao and Eltony, 2019;Chong and Dupps, 2021). In this study, we did not consider the viscous processes and a plastic deformation of the stroma during the surgical procedure.…”

A New Procedure to Estimate Patient-Specific Intraocular Pressure

“…A method to segment the clinical images of Corvis ST (a commercial NCT) is outlined and a function to approximate the movement of the corneal anterior section is proposed based on the function in [4]. A 2D axisymmetric CFD simulation is conducted with a moving boundary describing the movement of the cornea segmented from the images (Fig.…”