Measuring mechanical anisotropy of the cornea with Brillouin microscopy

• Published in: Nature communications Vol. 13; no. 1; pp. 1354 - 11
• Main Authors: Eltony, Amira M., Shao, Peng, Yun, Seok-Hyun
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15.03.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 631/1647/245/2226; 639/301/54/994; 639/624/1107/328; 639/624/1107/510; 639/624/1107/527; Animals; Anisotropy; Collagen; Cornea; Cornea - diagnostic imaging; Cornea - metabolism; Fibrils; Humanities and Social Sciences; Isotropic material; Lamellar structure; Light microscopy; Mechanical analysis; Mechanical properties; Microscopy; multidisciplinary; Optical microscopy; Optical properties; Science; Science (multidisciplinary); Stiffness coefficients; Stress, Mechanical; Swine; Tensors; Tissues
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-29038-5

Load-bearing tissues are typically fortified by networks of protein fibers, often with preferential orientations. This fiber structure imparts the tissues with direction-dependent mechanical properties optimized to support specific external loads. To accurately model and predict tissues’ mechanical response, it is essential to characterize the anisotropy on a microstructural scale. Previously, it has been difficult to measure the mechanical properties of intact tissues noninvasively. Here, we use Brillouin optical microscopy to visualize and quantify the anisotropic mechanical properties of corneal tissues at different length scales. We derive the stiffness tensor for a lamellar network of collagen fibrils and use angle-resolved Brillouin measurements to determine the longitudinal stiffness coefficients (longitudinal moduli) describing the ex vivo porcine cornea as a transverse isotropic material. Lastly, we observe significant mechanical anisotropy of the human cornea in vivo, highlighting the potential for clinical applications of off-axis Brillouin microscopy. Here, Brillouin optical microscopy noninvasively visualizes microscale anisotropy of the porcine cornea owing to its lamellar fiber structure and quantifies the longitudinal moduli of the bulk tissue. Anisotropy is also detected in angle-resolved measurement of the human cornea in vivo.