In vision correction surgeries, the corneal stroma is subject to limbal-relaxing incisions which change the focusing power of the cornea, but can damage tissue and put the patient at risk of complication. A non-invasive method to launch a mechanical wave in tissue, referred to as Acoustic Micro-Tapping (AuT), is demonstrated with phase-sensitive spectral domain OCT (SD-OCT) to probe for biomechanical changes in porcine and human cornea samples following arcuate keratotomy (AK). This method uses an air-coupled ultrasound transducer to deliver sufficient displacement on the corneal surface to launch a mechanical wave propagating as a guided mode. Rayleigh-Lamb wave propagation is captured at 100 spatial locations 6 mm across the corneal surface, resulting in a high resolution elastogram. The SD-OCT system operates in the MB mode at a functional frame rate of 47 kHz to detect local wave behavior for analysis of the group velocity, group displacement amplitude, displacement attenuation, phase velocity over the bandwidth of the excitation, mean frequency, and bandwidth. An analysis of mechanical wave behavior shows reduced wave speed up to 20% following an incision through 3/4th of the cornea in porcine tissue samples, indicating a potential reduction in elastic modulus. This technique was performed on porcine and human corneas following PRK incision to demonstrate progress toward clinical translation.
Mitchell A. Kirby, Liang Gao, Shaozhen Song, Ivan Pelivanov, David Li, Soon Joon Yoon, Tueng Shen, Ruikang Wang, and Matthew O’Donnell, "Non-contact detection of reduced corneal elasticity following refractive correction surgery
(Conference Presentation)," Proc. SPIE 10496, Optical Elastography and Tissue Biomechanics V, 104960B (Presented at SPIE BiOS: January 27, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2289350.5751469745001.
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