Characterization of porcine sclera using instrumented nanoindentation

Sclera tissue is the outermost protective layer of the eye and often involved in mechanical interactions during ocular medical procedures. In this study, instrumented nanoindentation is evaluated as a methodology for characterizing porcine sclera submerged in phosphate-buffered saline (PBS). Variances within a single sample and between samples are compared. Reduced modulus measurements are used to determine the effects of hydration, mounting conditions, and maximum applied load. Extended in vitro exposure beyond four hours to PBS is determined to decrease sample integrity. The use of glue to secure samples improved data consistency and had no negative effects on measurements. The data suggest that nanoindentation is a high precision method for measuring the reduced modulus of ultra low modulus soft tissue such as sclera (Er ~ 30 kPa) and illustrates the importance of environmental factors upon material properties.