Heartbeat Optical Coherence Elastography: Using Heartbeat to study Corneal Biomechanics
The cornea provides most of the eye’s refractive power. Severe corneal pathologies can therefore lead to visual impairment or complete vision loss. Alterations in the mechanical properties of the cornea often precede pathological developments, so measuring the tissue’s mechanical properties may be useful for diagnosing disease or monitoring therapeutic intervention. Elastography allows for direct measurement of mechanical properties and has been performed in the cornea through various imaging modalities, including ultrasound and optical coherence elastography (OCE). Typically, these measurements are performed in response to some type of external excitation. However, there is increasing interest in passive elastography, where the mechanical response to the natural physiological vibrations, such as the heartbeat, are detected. In this work, we demonstrate the use of heartbeat OCE (Hb-OCE) ex vivo and in vivo. Measurements are first performed in ex vivo porcine corneas to validate the feasibility of the technique. Pairs of eyes are separated into one group that is untreated and another group that is corneal collagen crosslinked (CXL) to increase tissue stiffness. Displacement is induced using a simulated ocular pulse, and stiffness is measured using an SD-OCT system. The results suggest that Hb-OCE can distinguish tissue stiffness. Hb-OCE was then demonstrated in an in vivo anesthetized rabbit, where pulse-induced displacement is detected using an SD-OCT system, and cardiac activity is concurrently measured using a pressure transducer on the animal’s chest. The results demonstrate the utility of this technique for in vivo assessment of corneal stiffness. Future work will be based on creating a quantitative model of stiffness and developing the truly noncontact technique for corneal elasticity measurement.
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Biomedical Optics Laboratory
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