Estimating Human Trabecular Meshwork Stiffness by Numerical Modeling and Advanced OCT Imaging.
Wang Ke, Johnstone Murray A, Xin Chen, Song Shaozhen, Padilla Steven, Vranka Janice A, Acott Ted S, Zhou Kai, Schwaner Stephen A, Wang Ruikang K
AI Summary
This study estimated human trabecular meshwork stiffness. Glaucomatous tissue was slightly stiffer, and stiffness correlated with outflow facility, suggesting TM biomechanics influence glaucoma.
Abstract
Purpose
The purpose of this study was to estimate human trabecular meshwork (hTM) stiffness, thought to be elevated in glaucoma, using a novel indirect approach, and to compare results with direct en face atomic force microscopy (AFM) measurements.
Methods
Postmortem human eyes were perfused to measure outflow facility and identify high- and low-flow regions (HF, LF) by tracer. Optical coherence tomography (OCT) images were obtained as Schlemm's canal luminal pressure was directly manipulated. TM stiffness was deduced by an inverse finite element modeling (FEM) approach. A series of AFM forcemaps was acquired along a line traversing the anterior angle on a radially cut flat-mount corneoscleral wedge with TM facing upward.
Results
The elastic modulus of normal hTM estimated by inverse FEM was 70 ± 20 kPa (mean ± SD), whereas glaucomatous hTM was slightly stiffer (98 ± 19 kPa). This trend was consistent with TM stiffnesses measured by AFM: normal hTM stiffness = 1.37 ± 0.56 kPa, which was lower than glaucomatous hTM stiffness (2.75 ± 1.19 kPa). None of these differences were statistically significant. TM in HF wedges was softer than that in LF wedges for both normal and glaucomatous eyes based on the inverse FEM approach but not by AFM. Outflow facility was significantly correlated with TM stiffness estimated by FEM in six human eyes (P = 0.018).
Conclusions
TM stiffness is higher, but only modestly so, in glaucomatous patients. Outflow facility in both normal and glaucomatous human eyes appears to associate with TM stiffness. This evidence motivates further studies to investigate factors underlying TM biomechanical property regulation.
MeSH Terms
Shields Classification
Key Concepts5
The elastic modulus of normal human trabecular meshwork (hTM) estimated by inverse finite element modeling (FEM) was 70 ± 20 kPa (mean ± SD), while glaucomatous hTM was slightly stiffer at 98 ± 19 kPa.
The stiffness of normal human trabecular meshwork (hTM) measured by atomic force microscopy (AFM) was 1.37 ± 0.56 kPa, which was lower than glaucomatous hTM stiffness (2.75 ± 1.19 kPa).
Outflow facility was significantly correlated with human trabecular meshwork (TM) stiffness estimated by inverse finite element modeling (FEM) in six human eyes (P = 0.018).
None of the differences in human trabecular meshwork (hTM) stiffness between normal and glaucomatous eyes, as estimated by inverse FEM or measured by AFM, were statistically significant.
Trabecular meshwork (TM) in high-flow (HF) wedges was softer than that in low-flow (LF) wedges for both normal and glaucomatous eyes based on the inverse FEM approach, but not by AFM.
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