Ultrasonic Speckle Tracking for Measurement of Scleral Cross-Sectional Strains due to Intraocular Pressure Elevation

Glaucomatous vision loss can occur at both normal and elevated levels of intraocular pressure (IOP) and the optic nerve head (ONH) is the principle site of damage. The mechanical environment of the ONH is believed to be critical for retinal ganglion cell pathophysiology [1]. Previous computational models have shown that scleral mechanical properties play an important role in affecting the mechanical environment of the ONH [2]. It is thus important to characterize the mechanical behavior of sclera under physiological loadings. Ultrasonic strain mapping has been developed to measure the internal displacement and strain of soft tissue under external loadings [3, 4]. The purpose of this study was to examine the cross-sectional strain maps at the posterior sclera under IOP elevations using non-invasive ultrasound and a speckle tracking algorithm.