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Ultrasonic Characterization of Corneal and Scleral Biomechanics

Tang, Junhua
http://rave.ohiolink.edu/etdc/view?acc_num=osu1354678642

Abstract Details

2012, Doctor of Philosophy, Ohio State University, Biomedical Engineering.
Cornea and sclera are the major load-bearing tissue of the eye and the biomechanics of the cornea and sclera have been shown to be critical in the understanding, diagnosis and management of glaucoma. It is therefore important to non-invasively measure the mechanical properties of the cornea and sclera and examine their effects in glaucoma. The current study was designed to investigate the effect of corneal stiffness on intraocular pressure (IOP) and central corneal thickness (CCT) measurements and develop ultrasound-based techniques for non-invasive characterization of corneal and scleral biomechanics under physiological loadings and configurations. We first examined the effect of the natural variation in speed of sound in cornea on the measurement of corneal thickness, which is an important parameter affecting the IOP measurement and a risk factor of glaucoma. The effect of the variation in corneal stiffness on IOP measurement was examined experimentally, and a non-invasive ultrasound method for measuring acoustic impedance was used to estimate the corneal stiffness and potentially provide corrections for IOP measurement. An ultrasound strain imaging method based on speckle tracking was developed to characterize the mechanical response of the sclera under IOP elevations, and the performance of the ultrasound method was evaluated both experimentally and using simulations. The mechanical responses of the porcine and human sclera under IOP elevations were then examined by this ultrasound strain imaging method. The variance of speed of sound in cornea was shown to potentially produce significant error in corneal thickness measurement using the current clinical setting of speed of sound in ultrasound pachymetry. Corneal acoustic impedance was significantly correlated with the speed of sound in cornea and could potentially be used to improve corneal thickness measurement accuracy. The effect of corneal stiffness on IOP measurement was found to be significant, and the corneal acoustic impedance was significantly correlated with the IOP measurement error and the corneal stiffness measured through uniaxial tests. This correlation may provide necessary corrections for clinical IOP measurement. The ultrasound speckle tracking method developed for noninvasive measurement of through-thickness distributive strains of the sclera demonstrated excellent accuracy and high signal-to-noise ratio in both experimental and simulation results. The porcine and human sclera showed anisotropic, nonlinear, heterogeneous mechanical responses under IOP elevations. The current study demonstrated significant effects of corneal biomechanics on CCT and IOP measurement and the complexity of sclera biomechanics in response to IOP loadings. This research also established the feasibility of the proposed ultrasound methods as useful experimental and clinical tools to characterize corneal and scleral biomechanics non-invasively. Future studies should implement these techniques for measurement of corneal and scleral biomechanical properties in glaucoma patients.
Jun Liu, PhD (Advisor)
Richard Hart, PhD (Committee Member)
Paul Weber, MD (Committee Member)
Cynthia Roberts, PhD (Committee Member)
172 p.
Biomechanics; Biomedical Engineering; Ophthalmology
ultrasound; ultrasound elastography; corneal biomechanics; scleral biomechanics; glaucoma

Recommended Citations

Citations

  • Tang, J. (2012). Ultrasonic Characterization of Corneal and Scleral Biomechanics [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354678642

    APA Style (7th edition)

  • Tang, Junhua. Ultrasonic Characterization of Corneal and Scleral Biomechanics. 2012. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1354678642.

    MLA Style (8th edition)

  • Tang, Junhua. "Ultrasonic Characterization of Corneal and Scleral Biomechanics." Doctoral dissertation, Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354678642

    Chicago Manual of Style (17th edition)

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© 2012, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.