Evaluation of the biomechanical properties of the posterior eye using Shear Wave Elastography in patients with increased intracranial pressure

Abstract

Aims: This study aims to investigate the biomechanical properties of the posterior eye using the shear wave elastography (SWE) in increased intracranial pressure (ICP) patients and healthy subjects. Material and methods:This study enrolled 54 healthy subjects and 54 patients with increased ICP, including 29 patients with space-occupying lesions (SOLs) and 25 patients with intracranial haemorrhage (ICH). Optic nerve sheath diameter and the stiffness of the optic nerve head, peripapil-lary sclera and optic nerve were evaluated. Results:Patients with increased ICP had a significantly higher optic nerve sheath diameter, Young’s modulus of optic nerve head, and Young’s modulus of peripapillary sclera than healthy subjects (p<0.01 for all). The optic nerve sheath diameter, Young’s modulus of optic nerve head and Young’s modulus of the peripapillary sclera were similar between the SOLs group and ICH group (p>0.05 for all). Young’s modulus of the optic nerve in the ICH group was similar to the control group (p>0.05), whereas the SOLs group had higher Young’s modulus of optic nerve comparing the control group (p<0.05). Conclusion: The stiffness of the optic nerve head and peripapillary sclera were higher in patients with increased ICP than healthy subjects, and the optic nerve stiffness of SOLs patients was the highest in all subjects. The SWE could provide a quantitative analysis of the posterior eye’s biomechanical properties and help the clinic diagnose the degree of visual impairments.

Long-Term Remodeling Response in the Lamina Cribrosa Years after IOP Lowering by Suturelysis after Trabeculectomy

“…42 The result may be due to the thinner structure of a glaucoma LC, changes in the material properties of the LC with glaucoma damage, or a combination of both factors. While there has been some evidence that the sclera, overall, is less compliant with experimental glaucoma and in human glaucoma eyes, [46][47][48][49][50][51][52][53] we determined that in vitro mechanical responses are more compliant in eyes with greater pre-mortem glaucoma damage. 54 Furthermore, recent histological studies found that eyes with greater axon loss had thinner LC connective tissue beams.…”

Quantitative Microstructural Analysis of Cellular and Tissue Remodeling in Human Glaucoma Optic Nerve Head

“…In human eyes with glaucoma, the mechanical properties of the equatorial sclera have been reported to be stiffer in glaucoma eyes compared to non-glaucoma eyes by in vivo indirect measurements. 67 – 69 Experimental IOP elevation in monkeys produces a variably stiffer mechanical response in the overall sclera compared to controls. 70 – 72 Further estimates of scleral and ONH mechanics have been made by ex vivo inflation testing in animal 73 – 78 and human 79 – 83 eyes, which commonly shows far less strain in the sclera than the ONH itself, suggesting lower strain in glaucoma ONH.…”

Glaucoma and biomechanics

“…For instance, by employing elastography, a noninvasive imaging-based technique that uses mechanical waves, one can directly probe the biomechanical properties of tissues in vivo . Xiao et al [119] used ultrasonic shear wave elastography to show that patients with increased intracranial pressure (ICP) have a stiffer ONH, and this technique can potentially be used to measure changes to the mechanical properties of the ONH in glaucoma patients. In addition, using ex vivo ultrasonic elastography of porcine eyes it was shown that elevation of IOP increases ONH stiffness [120], and causes a nonhomogenous strain field on the ONH [121], important in understanding the relation between ONH mechanics and the patterns of vision loss in glaucoma.…”