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Thu-Mai Nguyen, Kate Grieve, Michel Paques, Claude Boccara, Christophe Baudouin, Zwillinger Stephanie; Stiffness of glaucomatous sclera assessed using Optical Coherence Dynamic Elastography: a preliminary ex vivo study. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1714.
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© 2017 Association for Research in Vision and Ophthalmology.
To compare the stiffness of sclera in primary open angle glaucoma patients versus healthy controls using a non-invasive elastography method.
Optical Coherence Dynamic Elastography is a recent development of Optical Coherence Tomography (OCT) that maps tissue stiffness by observing the tissue response to a mechanical dynamic stimulus. Our setup uses a piezoelectric actuator to generate propagating shear waves in tissue and a high line-rate spectral-domain OCT to track the resulting micron-scale displacements. Their propagation speed v is linked to the tissue Young’s modulus E by: E = 3ρv2, where ρ is the tissue density. Healthy sclera samples were collected from human donor corneas at the eye bank. Glaucomatous samples were collected from patients undergoing non-penetrating sclerectomy, stored in CorneaJet graft storage medium and imaged within a few hours after surgery. For each sample, stiffness was mapped over a cross-section of 3.8mm x 2mm with a pixel size of 15 µm x 5 µm (lateral x depth). The median value of the shear wave speed was then computed over the entire cross-section.
Stiffness maps were obtained on a healthy and a glaucomatous sample. Sclera samples from glaucomatous patients exhibit a higher shear wave speed (7.3 ± 1.4 m/s, N=8) than healthy donors (6.3 ± 0.4 m/s, N=4). These preliminary experiments suggest that sclera of glaucomatous patients are significantly stiffer than that of healthy donors.
Our results are consistent with previous ex vivo biomechanical and microstructural studies reported in the literature. The increased stiffness of glaucomatous sclera could arise from tissue reorganization in this pathology. Since our method is non-invasive, in vivo measurements are envisioned in further studies for optimum physiological conditions. This could improve our understanding of the physiopathology of glaucoma.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Figure – Cross-section of sclera samples (A: healthy, B: glaucomatous). Gray scale: morphologic image. Color scale: stiffness map (the higher the speed is, the stiffer the tissue is).
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