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Cornea Full-field Displacement and Strain Measurement in Vivo Using Three-dimensional Digital Image Correlation

Zhang, Xueyong, PhD1,2*; Wang, Qing, MD3; Wang, Like, MD1; Xiao, Hong, MD4; Zhang, Daming, PhD2; Liao, Rongfeng, PhD3; Zheng, Yongping, PhD1

doi: 10.1097/OPX.0000000000001292
ORIGINAL INVESTIGATIONS

SIGNIFICANCE Corneal biomechanics are becoming increasingly important for clinical evaluation and diagnosis, such as in refractive surgery, glaucoma, and keratoconus. We developed and used a new technique to measure the full-field displacement and strain of the cornea under elevated intraocular pressure in vivo.

PURPOSE In this study, we propose a three-dimensional digital image correlation method for the determination of corneal biomechanical properties.

METHODS Corneal deformation change on the rabbit eyeball was investigated under different inflation conditions with intraocular pressure levels of 2.3, 3.3, 5.3, and 6.9 kPa in vivo.

RESULTS The proposed method was able to measure the displacement of the corneal surface and to construct real-time full-field three-dimensional deformation vector fields and strain mapping. The results show that the strain distribution is not uniform on the corneal surface at each intraocular pressure level. Compression strains, rather than extensile strains, are dominant at the corneal apex region.

CONCLUSIONS This technique has the potential to be used as an assistive tool for the determination of corneal biomechanical properties in ophthalmologic investigations.

1Interdisciplinary Division of Biomedical Engineering, Hong Kong Polytechnic University, Kowloon, Hong Kong, China

2School of Mathematics and Physics, Anhui Jianzhu University, Hefei, China

3Department of Ophthalmology, The First Affiliated Hospital of Anhui Medical University, Hefei, China

4School of Information Science and Technology, University of Science and Technology of China, Hefei, China *xyzhang_aua@126.com

Submitted: October 21, 2017

Accepted: June 20, 2018

Funding/Support: National Natural Science Foundation of China (61471003; to XZ); Hong Kong Polytechnic University Joint PhD Supervision Scheme (G-UB58; to YZ); and Hong Kong Scholars Program (XJ2012044; to XZ).

Conflict of Interest Disclosure: None of the authors have a financial conflict of interest.

Study Registration Information: This study was approved by the institution’s Committee of Ethics (Anhui Medical University). Registration/Protocol Number: 2016-0029.

Author Contributions: Conceptualization: XZ; Data Curation: QW, HX, DZ; Formal Analysis: XZ, DZ, YZ; Funding Acquisition: XZ, LW, YZ; Investigation: XZ, QW, HX, DZ, RL; Methodology: XZ, HX; Project Administration: XZ, YZ; Supervision: XZ, YZ; Validation: LW, RL; Visualization: HX, DZ; Writing – Original Draft: XZ; Writing – Review & Editing: XZ, LW, YZ.

© 2018 American Academy of Optometry