Delineating corneal elastic anisotropy in a porcine model using non-contact optical coherence elastography and ex vivo mechanical tests

Objective: To compare non-contact acoustic micro-tapping optical coherence elastography (AuT-OCE) with destructive mechanical tests to confirm corneal elastic anisotropy. Design: Ex vivo, laboratory study with non-contact AuT-OCE followed by mechanical rheometry and extensometry. Subjects: Inflated cornea of whole-globe porcine eyes. Methods: A non-contact transducer was used to launch mechanical waves in the cornea that were imaged with phase-sensitive OCT at physiologically relevant pressures. Reconstruction of both Young's modulus (E) and out-of-plane shear modulus (G) in the cornea from experimental data was performed using a model of a nearly incompressible transversally isotropic (NITI) medium. Samples were then excised and parallel plate rheometry was performed to measure the shear modulus G. Corneal samples were then subjected to strip extensomety to measure the Young's modulus. Main Outcome Measures: Strong corneal anisotropy was confirmed with both AuT-OCE and mechanical tests, with the Young's and shear moduli differing by over an order of magnitude. These results show that AuT-OCE can quantify both moduli with a non-contact, non-invasive, clinically translatable technique.