Measuring Human Corneal Stromal Biomechanical Properties Using Tensile Testing Combined With Optical Coherence Tomography

Yi Song; Di Wu; Min Shen; Like Wang; Congzheng Wang; Yong Cai; Chao Xue; George P M Cheng; Yongping Zheng; Yan Wang

doi:10.3389/fbioe.2022.882392

Measuring Human Corneal Stromal Biomechanical Properties Using Tensile Testing Combined With Optical Coherence Tomography

Front Bioeng Biotechnol. 2022 May 20:10:882392. doi: 10.3389/fbioe.2022.882392. eCollection 2022.

Authors

Yi Song¹, Di Wu^{2

3}, Min Shen⁴, Like Wang⁵, Congzheng Wang⁴, Yong Cai¹, Chao Xue², George P M Cheng⁶, Yongping Zheng^{5

7}, Yan Wang^{1

2

8}

Affiliations

¹ Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China.
² Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Tianjin, China.
³ Pacific University College of Optometry, Forest Grove, OR, United States.
⁴ School of Mechanical Engineering, Tianjin University, Tianjin, China.
⁵ Department of Biomedical Engineering, The Hong Kong Polytechnic University, Hong Kong, China.
⁶ School of Optometry, The Hong Kong Polytechnic University, Hong Kong, China.
⁷ Research Institute for Smart Ageing, The Hong Kong Polytechnic University, Hong Kong, China.
⁸ Nankai University Eye Institute, Nankai University Affiliated Eye Hospital, Nankai University, Tianjin, China.

Abstract

Purpose: To investigate the ex vivo elastic modulus of human corneal stroma using tensile testing with optical coherence tomography (OCT) imaging and its correlation with in vivo measurements using corneal visualization Scheimpflug technology. Methods: Twenty-four corneal specimens extracted from stromal lenticules through small incision lenticule extraction were cut into strips for uniaxial tensile tests. In vivo corneal biomechanical responses were evaluated preoperatively using the corneal visualization Scheimpflug technology (CorVis ST). The correlation of the elastic modulus with clinical characteristics and dynamic corneal response parameters were analyzed using Spearman's correlation analysis. Results: The mean low strain tangent modulus (LSTM) of the human corneal stroma was 0.204 ± 0.189 (range 0.010-0.641) MPa, and high strain tangent modulus (HSTM) 5.114 ± 1.958 (range 2.755-9.976) MPa. Both LSTM (r = 0.447, p = 0.029) and HSTM (r = 0.557, p = 0.005) were positively correlated with the stress-strain index (SSI). LSTM was also positively correlated with the A1 deflection length (r = 0.427, p = 0.037) and A1 deflection area (r = 0.441, p = 0.031). HSTM was positively correlated with spherical equivalent (r = 0.425, p = 0.038). Conclusions: The correlation of corneal elastic modulus with A1 deflection parameters and SSI may indicate a relationship between these parameters and tissue elasticity. The HSTM decreased with the degree of myopia. Combining tensile test with OCT may be a promising approach to assess corneal biomechanical properties.

Keywords: biomechanical properties; cornea; dynamic response parameters; myopia; optical coherence tomography; tensile testing.