This document summarizes a student's research modeling the effects of Bruch's membrane opening (BMO) shape on biomechanics in a rat glaucoma model. The student created 2D models of the eye with varying BMO shapes in simulation software and found strain levels varied by up to 30% between shapes. This suggests BMO shape could impact susceptibility to damage from elevated intraocular pressure in glaucoma. The student also conducted summer research treating pig trabecular meshwork cells with saponin to develop a glaucoma model by killing approximately 80% of the cells.

1. Modeling the Effects of Bruch’s Membrane
Opening Shape on the Biomechanics of the Rat
Model of Glaucoma
Nicole Gullatt
Dr. C. R. Ethier’s Lab
Mentor: Stephen Schwaner
May 16, 2016

2. Glaucoma Overview: What is it?
• Glaucoma is a group of eye diseases involving optic nerve damage and usually involving an increase of intra-ocular
pressure (IOP)
• Elevated IOP causes increased stressed and strain in the optic nerve head (ONH) tissues resulting in retinal ganglion
cell death and preventing the transmission of visual information to the brain
• Treatment for glaucoma is centered around preventing further loss because eye damage and vision loss that has already
occurred is irreversible
• Medications and surgical treatments for glaucoma focus on lowering a patient’s IOP, but are not always effective
Why the rat model is studied for glaucoma research:
 It is unethical to conduct scientific experiments on humans.
 Rodent models are necessary for high throughput studies due to their low cost and ease of caring for
 Rats present similar optic nerve head damage patterns to humans after experiencing elevated IOP

3. Biomechanics of the Optic Nerve Head (ONH)
• The complex pathophysiology of glaucoma is
driven by biomechanics
• Elevated IOP leads to stress and strain in the
ONH.
 Stress: force per unit area
 Strain: ratio of an object’s deformation to its
original shape
• IOP related stress and strain can affect the delivery
of nutrients to the RGC axons and axonal
transport, and the activation of astrocytes in the
ONH
• Distribution of stress and strain in the ONH is
complicated

4. My Research Focus: Computer Modeling
1. Use design program Multiview to obtain
3-D point clouds of tissue geometry
2. Create 2-D circular plane (radius: 1 mm)
with BMO shape in Rhino
3. Import 2-D plane into Abaqus and assign
material properties:
 Young’s Modulus: 3 MPa
 Poisson’s Ratio: 0.49
Multiview Delineations of Histology
Slide MR4-OD
BMO shapes acquired
in Multiview
Circular Plane
Rhino
Circular Plane with material
properties in Abaqus

5. My Research Focus: Computer Modeling
4. Create polar coordinate system for 2-D Plane
Section in Abaqus
 Biaxial Displacement: 10 µm in radial direction
 Boundary Condition: constrained in z direction
5. Mesh 2-D Plane in Abaqus
 Meshing breaks geometrical figures into elements
6. Simulate stress and strain levels at locations in the
eye using Abaqus
2-D Plane with loads and
boundary conditions in Abaqus
Meshed 2-D Plane with
elements in Abaqus
Solve the model in Abaqus
to simulate strain levels around BMO

6. Results

7. Conclusion
 Differences in 95th percentile strain of up to 30% were predicted between models.
 This suggests that BMO shape could be an important factor in the rat model of glaucoma and that a more irregular BMO shape
could potentially increase susceptibility to IOP-related damage in glaucoma.

8. Summer Research: Saponin Treatments for Pig TM Cells
• The trabecular meshwork is an area of tissue in the eye located around the cornea, responsible for
removing the aqueous humor from the eye.
• Project Goal: Find the appropriate concentration of saponin to kill approximately 80% of pig trabecula
meshwork cells to develop a glaucoma model.

9. Acknowledgments
• I wish to acknowledge Dr. C. R. Ethier, Stephen Schwaner, Eric Snider, and members of
the Either Lab for their assistance with this research.
• Thank You!