In vivo optical coherence elastography of the cornea: mapping shear and tensile moduli

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ABSTRACT The mechanical stability of the cornea supports visual acuity by maintaining corneal curvature, with important implications for refractive surgery and the management of cornea ectasia. However, clinical options for mechanical characterization are limited, particularly when compared to well-established tools for morphological characterization of the cornea. Several commercial and investigational instruments have highlighted the potential value of corneal biomechanical analysis, but these devices have limited accuracy and cannot fully characterize the anisotropic, nonlinear, and spatially varying elastic stiffness of the cornea. The overarching goal of this project is to develop advanced optical coherence elastography (OCE) for comprehensive characterization of corneal biomechanics. The proposed technology harnesses both extensional and flexural elastic waves guided along the cornea to measure in-plane tensile (Young’s) and shear moduli at mm-scale resolution. The first specific aim is to develop an OCE system using non-contact ultrasound transducers optimized to excite both elastic waves efficiently at high frequencies spanning 4- 10 kHz. The second specific aim is to test this OCE system with healthy subjects and investigate the dependence of tensile and shear moduli on age and intraocular pressure in vivo. The third specific aim is to measure tensile and shear moduli in patients diagnosed with keratoconus and to monitor mechanical changes after corneal crosslinking treatment. The fourth specific aim is to analyze changes in the moduli as a result of different corneal refractive surgeries. Various ex vivo measurements and finite-element modeling studies will also be undertaken in order to interpret the clinical data and relate the measured moduli to the microstructure of the cornea. This project will advance our understanding of corneal biomechanics in relation to various natural, pathological, and interventional processes and may lead to a new clinical tool that can improve the diagnosis and treatment of keratoconus, the safety and visual outcome of refractive surgery, and the accuracy of tonometry.