Assessing the mechanical anisotropy and hysteresis while cycling IOP of porcine eyes before and after CXL by noncontact optical coherence elastography

Diseases such as keratoconus can alter the orientation of collagen fibrils in the cornea. Moreover, therapeutic interventions such as UV-A/riboflavin corneal collagen crosslinking (CXL) can alter the collagen fibril arrangement. Therefore, the anisotropic characteristics of the cornea can provide vital information about tissue integrity. In this work, we utilize noncontact elastic wave imaging optical coherence elastography (EWI-OCE) to assess the elastic anisotropy and hysteresis of in situ porcine corneas as various intraocular pressures (IOP). In addition, we evaluated the effects of CXL on the mechanical anisotropy and hysteresis. OCE measurements were made at stepped meridional angles, and a sliding window algorithm spatially mapped the elasticity. A modified planar anisotropy coefficient was utilized to quantify the elastic anisotropy of the corneas. The results show that the stiffness and elastic anisotropy of the corneas were significantly affected by CXL and IOP (P<0.001), but the hysteresis was not significant (P<0.05). Moreover, the changes in elasticity due to CXL were angle-dependent (P<0.005). However, the changes in mechanical anisotropy from CXL were not angle-dependent (P>0.05).