Regional Biomechanical Weakening in Keratoconus Corneas Detected by In Vivo High-Frequency Ultrasound Elastography

Purpose: In vivo biomechanical characterization of the cornea remains a challenge. We have developed a high-resolution ultrasound elastography technique, termed ocular pulse elastography (OPE), to measure corneal deformation in response to the intraocular pressure (IOP) pulsation at each heartbeat. In this study, we aimed to compare corneal axial strains (CASs) between patients with keratoconus and normal subjects and evaluate the spatial mapping of CAS in high grade keratoconus. Methods: Forty patients with keratoconus (63 eyes) and 40 normal controls (80 eyes) were enrolled in this study. Each eye underwent 4 ultrasound measurements using the Vevo2100 high-frequency ultrasound system. Each measurement acquired 1000 continuous B-mode scans in 8 seconds. Corneal axial displacements and strains were quantified using an ultrasound speckle tracking algorithm. Results: CAS magnitude was significantly higher in keratoconus than normal corneas (-0.13% +/- 0.09% vs. -0.06% +/- 0.04%, P < 0.001) with an increasing trend in higher grades (P < 0.001). CAS in keratoconus corneas had a greater spatial variance as higher strains were observed in the cone center than its surrounding regions in grade 3 and 4 keratoconus corneas. Conclusions: Our results showed that high-frequency ultrasound elastography was able to detect and quantify the larger deformation of keratoconus corneas than normal corneas in response to the natural fluctuations of IOP at each heartbeat, and it also detected the spatial variance showing greater deformation in the cone region. Translational Relevance: High-resolution ultrasound may provide a sensitive tool for quick, spatially resolved characterization of corneal biomechanics to aid keratoconus detection and diagnosis.