Non-contact acoustic micro-tapping optical coherence elastography for quantification of corneal anisotropic elasticity: in vivo rabbit study

PURPOSE. To demonstrate accurate measurement of corneal elastic moduli in vivo with non-contact and non-invasive optical coherence elastography. METHODS. Elastic properties (in-plane Young’s modulus E and both in-plane, μ, and out-of-plane, G, shear moduli) of rabbit cornea were quantified in vivo using non-contact dynamic Acoustic micro-Tapping Optical Coherence Elastography (AμT-OCE). The IOP-dependence of measured mechanical properties was explored in extracted whole globes following in vivo measurement. A nearly-incompressible transverse isotropic (NITI) model was used to reconstruct moduli from AμT-OCE data. Independently, cornea elastic moduli were also measured ex vivo with traditional, destructive mechanical tests (tensile extensometry and shear rheometry). RESULTS. Our study demonstrates strong anisotropy of corneal elasticity in rabbits. The in-plane Young’s modulus, computed as E = 3μ, was in the range of 20–44 MPa, whereas the out-of-plane shear modulus was in the range of 34–261 kPa. Both pressure-dependent ex vivo OCE and destructive mechanical tests performed on the same samples within an hour of euthanasia strongly support the results of AμT-OCE measurements. CONCLUSIONS. Non-contact AμT-OCE can non-invasively quantify cornea anisotropic elastic properties in vivo. TRANSLATIONAL RELEVANCE. As OCT is broadly accepted in Ophthalmology, these results suggest the potential for rapid translation of AμT-OCE into clinical practice. In addition, AμT-OCE can likely improve diagnostic criteria of ectatic corneal diseases, leading to early diagnosis, reduced complications, customized surgical treatment, and personalized biomechanical models of the eye.