Heartbeat-induced corneal axial displacement and strain measured by high frequency ultrasound elastography in human volunteers
Sunny Kwok, Keyton Clayson, Nicholas Hazen, Xueliang Pan, Yanhui Ma, Andrew J. Hendershot, Jun LiuTranslational Vision Science and Technology2020
Purpose: The purpose of this study was to establish in vivo data acquisition and processing protocols for repeatable measurements of heartbeat-induced corneal displacements and strains in human eyes, using a high-frequency ultrasound elastography method, termed ocular pulse elastography (OPE). Methods: Twenty-four volunteers with no known ocular diseases were recruited for this study. Intraocular pressure (IOP) and ocular pulse amplitude (OPA) were measured using a PASCAL Dynamic Contour Tonometer (DCT). An in vivo OPE protocol was developed to measure heartbeat-induced corneal displacements. Videos of the central 5.7 mm of the cornea were acquired using a 50-MHz ultrasound probe at 128 frames per second. The radiofrequency data of 1000 frames were analyzed using an ultrasound speckle tracking algorithm to calculate corneal displacements and quantify spectral and tempo-ral characteristics. The intrasession and intersession repeatability of OPE-and DCT-measured parameters were also analyzed. Results: The in vivo OPE protocol and setup were successful in tracking heartbeat-induced corneal motion using high-frequency ultrasound. Corneal axial displacements showed a strong cardiac rhythm, with good intrasession and intersession repeatabil-ity, and high interocular symmetry. Corneal strain was calculated in two eyes of two subjects, showing substantially different responses. Conclusions: We demonstrated the feasibility of high-frequency ultrasound elastogra-phy for noninvasive in vivo measurement of the cornea’s biomechanical responses to the intrinsic ocular pulse. The high intrasession and intersession repeatability suggested a robust implementation of this technique to the in vivo setting. Translational Relevance: OPE may offer a useful tool for clinical biomechanical evaluation of the cornea by quantifying its response to the intrinsic pulsation.