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Xuejun Qian, Teng Ma, Heur Martin, Jun Zhang, K. Kirk Shung, Mark S Humayun, Qifa Zhou; Ultrasonic Micro-elastography for Accessing Biomechanical Properties of the Cornea. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4331. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Noninvasive determination of biomechanical properties of the cornea could prove to be clinically useful. It can help determine the risk of post-refractive keratectasia and more accurately determine the true intraocular pressure (IOP).
A novel dual frequency ultrasonic micro-elastography imaging system was developed to enable the point-to-point mapping of biomechanical properties of corneal tissue, consisting a 4.5 MHz ring transducer and a confocally aligned 40 MHz needle transducer (PIN-PMN-PT single crystal) for sufficient excitation and precise detection of micro-level displacements, respectively. First, the spatial resolution and field of view of our imaging system was initially validated on gelatin tissue-mimicking phantoms. Next, imaging was performed on porcine corneas that were either crosslinked using aldehyde or where the intraocular pressure was varied to map the morphological structure and stiffness within the cornea.
The axial and lateral resolution of ultrasonic micro-elastography imaging system are characterized to be 83 and 151 μm, respectively, which is found to be sufficient enough for quantifying the biomechanical properties of cornea. Increasing stiffness could be observed on elastography with increasing duration of crosslinking, and the elastography data correlated well with histology in the crosslinked corneas (Fig.1). Increasing IOP led to a stiffer cornea and sclera without obvious changes in corneal thickness and curvature. It was interesting to note that there was a difference in the stiffness between the anterior and posterior corneas under various IOPs.
Our results demonstrate proof of principle of using ultrasonic micro-elastography to image the biomechanical properties of the cornea with fine resolution (< 100 µm). Further studies are needed to determine the clinical utility of ultrasonic micro-elastography.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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