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

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.