Transcript Presentation

The effects of curvature and thickness of corneabased structures assessed by finite element modeling
and optical coherence elastography
Zhaolong Han, Jiasong Li, Manmohan Singh, Salavat R. Aglyamov, Chen Wu,
Chih-hao Liu, and Kirill V. Larin
Department of Biomedical Engineering,
University of Houston
Outline
•
•
•
•
Introduction
Methods
Results
Conclusion
Introduction
• One approach for extracting the biomechanical properties of the cornea is
by assessing the propagation of an elastic wave by Optical Coherence
Elastography (OCE).
• However, the wave models currently used to quantify the biomechanical
properties are based on the assumption of a thin plate in half-space, which
does not incorporate the effects of the thickness and curvature of the
cornea.
• We have performed finite element (FE) simulations combined with OCE
experiments in order to understand the influence of the corneal curvature
and thickness on the group velocity of an elastic wave.
Methods: OCE setup
OCE set up
J. Li, et al, "Dynamic optical coherence tomography measurements of elastic wave propagation in tissue-mimicking
phantoms and mouse cornea in vivo," J Biomed Opt 18(12), (2013).
Methods: cornea-shape samples
Contact lens
Alcon Inc., TX, USA;
67% delefilcon A, 33% water
Phantom strip on a water balloon
Methods: FEM models
FEM model
Excitation
Four types of cornea-like structures
Results: radius effect
Both FEM and OCE experiments
demonstrate that group velocity
decreases as radius of curvature
increases.
Results: thickness effect
Both FEM and OCE experiments demonstrate that group velocity
increases with thickness.
Results: FEM displacement map
Different FEM simulated displacement contour maps
(2D and 3D views) at t=3.2 ms for different cornea-shape
under the same Young’s modulus E=60kPa.
Results: FEM displacements
FEM simulated vertical displacement temporal profiles
obtained at 0.16 mm, 0.80 mm, 1.44 mm and 2.08 mm away
from the central excitation for the four types of structures.
Conclusions
• In cornea-shape structure, the group velocity decreases
as the radius of curvature increases, and that the velocity
increases as the thickness of the sample increases.
• The curvature and thickness must be considered when
improving wave models used for reconstructing the
biomechanical properties of the cornea from OCE
measurements.
• Combining OCE with FEM is a promising method to
quantitatively reconstruct elasticity in cornea.
Thank you!