Hydration related changes in tensile response of posterior porcine sclera.

It has been shown that there exists significance dependence between hydration and biomechanical properties of hydrated tissues such as cornea. The primary purpose of this study was to determine hydration effects on mechanical properties of sclera. Scleral strips, dissected from the posterior part of pig eyes along the superior-inferior direction, were divided into four hydration groups by first drying them and then soaking them in PBS until their hydration reached to 75%, 100%, 150%, and 200%. The strips were subjected to ten consecutive cycles of loading and unloading up to 1 MPa. The response of samples at the tenth cycle was used to compute the tangent modulus, maximum strain, and hysteresis as a function of hydration. The experiments were done in oil in order to prevent hydration changes during the mechanical tests. The mechanical response of strips right after dissection, control group, was also measured. In general, significant softening of scleral strips was found with increasing hydration (p < 0.05). The stress-strain response of control group was between those of samples with hydration 150% and 200%. The experimental stress-strain data were successfully represented numerically with an exponential mathematical relation with R > 0.99. The present study showed that hydration would significantly alter the tensile response of scleral tissue. Thus, the hydration of scleral specimens during mechanical experimental measurements should be carefully controlled.