Characterizing lamina cribrosa and peripapillary sclera deformation using 3D ultrasound elastography

Abstract

Purpose : Lamina cribrosa (LC) and peripapillary sclera (PPS) biomechanical deformation is linked to intraocular pressure (IOP) induced glaucomatous damages. Previous studies have characterized PPS or LC deformation, but few measured the deformation of both tissues in the same eye. In this study, we used a 3D high-frequency ultrasound elastography technique to simultaneously characterize LC and PPS deformation in human donor eyes during IOP elevation.

Methods : Inflation tests were performed in 10 human donor (49–74 years old) whole globes while IOP was raised from 15 to 30 mmHg at 2-5 mmHg steps. A 3D volume of the posterior eye centered at the ONH was scanned at each pressure step using a 50MHz ultrasound probe (Vevo2100, VisualSonics; Fig. 1). A correlation-based 3D speckle tracking algorithm was used to compute tissue displacements. Radial (ε_rr), meridional (ε_φφ), circumferential (ε_θθ), and shear (ε_θr, ε_φr and ε_θφ) strains in spherical coordinates were obtained. PPS and LC were manually segmented in radial views reconstructed using a custom software, Multiview. Average strains in LC and PPS were obtained for each eye.

Results : All strains within LC and PPS increased with IOP elevation (Fig. 2). At 30 mmHg, out-of-plane shear strains ε_φr and ε_θr and radial strain ε_rr had the largest magnitudes in both LC (2.16%, 2.01%, 1.92%, respectively) and PPS (1.69%, 1.85%, 4.00%, respectively). Other types of strains were less than 1% on average. Shear strain ε_φr was correlated between LC and PPS (R=0.69, 95% CI: 0.10, 0.92) and significantly higher in LC than PPS (2.16% vs 1.69%, p=0.018). Radial strain ε_rr was larger in PPS than LC (4.00% vs 1.92%, p=0.006).

Conclusions : This study showed that 3D high-frequency ultrasound was capable of simultaneously imaging and quantifying PPS and LC deformation through full tissue thickness in human donor eyes. Out-of-plane shear and radial strains were the dominant types of deformation in LC and PPS, while in-plane strains were generally small. This study provides new insights into IOP-related biomechanical insults at LC and PPS, the critical sites of damage in glaucoma.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Fig.1: Reconstructed 3D ultrasound images of the posterior eye were manually segmented for LC, PPS, scleral canal, and retina.

 

Fig. 2: LC and PPS strains increased with IOP elevation. * denotes significant difference between LC and PPS in two types of strains (ε_φr and ε_rr).