Instrumented indentation for determination of mechanical properties of human cornea after ultraviolet-A crosslinking.

UVA crosslinking is used for treatment of corneal diseases such as keratoconus in order to stabilize the corneal tissue by crosslinking of the collagen fibers. It has been shown that the crosslinking treatment leads to a stiffening of the central corneal tissue. However, knowledge of lateral extent of the corneal stiffening as well as a systematic study of the mechanical response of human cornea is still missing. In our study we measured the stiffness (elastic modulus) of the anterior surface of healthy and crosslinked human corneas by instrumented indentation using a spherical indenter. The results show that the stiffness of the central and paracentral cornea increased almost two times after the crosslinking but the stiffening effect rapidly decreased towards the periphery of the radiation field. These new insights into the understanding of the biomechanical response of corneal crosslinking shall contribute to a better understanding and an optimization of this perspective medical treatment. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1413-1420, 2018.