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Research Papers

Evaluation of Different Projectiles in Matched Experimental Eye Impact Simulations

[+] Author and Article Information
Ashley A. Weaver

Center for Injury Biomechanics, Virginia Tech-Wake Forest University, Winston-Salem, NC 27157; School of Medicine, Wake Forest University, Winston-Salem, NC 27157

Eric A. Kennedy

Department of Biomedical Engineering, Bucknell University, Lewisburg, PA 17837

Stefan M. Duma

Center for Injury Biomechanics, Virginia Tech-Wake Forest University, Blacksburg, VA 24061; Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

Joel D. Stitzel1

Center for Injury Biomechanics, Virginia Tech-Wake Forest University, Winston-Salem, NC 27157; School of Medicine, Wake Forest University, Winston-Salem, NC 27157jstitzel@wfubmc.edu

1

Corresponding author.

J Biomech Eng 133(3), 031002 (Feb 04, 2011) (10 pages) doi:10.1115/1.4003328 History: Received August 29, 2010; Revised November 22, 2010; Posted January 03, 2011; Published February 04, 2011; Online February 04, 2011

Eye trauma results in 30,000 cases of blindness each year in the United States and is the second leading cause of monocular visual impairment. Eye injury is caused by a wide variety of projectile impacts and loading scenarios with common sources of trauma being motor vehicle crashes, military operations, and sporting impacts. For the current study, 79 experimental eye impact tests in literature were computationally modeled to analyze global and localized responses of the eye to a variety of blunt projectile impacts. Simulations were run with eight different projectiles (airsoft pellets, baseball, air gun pellets commonly known as BBs, blunt impactor, paintball, aluminum, foam, and plastic rods) to characterize effects of the projectile size, mass, geometry, material properties, and velocity on eye response. This study presents a matched comparison of experimental test results and computational model outputs including stress, energy, and pressure used to evaluate risk of eye injury. In general, the computational results agreed with the experimental results. A receiver operating characteristic curve analysis was used to establish the stress and pressure thresholds that best discriminated for globe rupture in the matched experimental tests. Globe rupture is predicted by the computational simulations when the corneoscleral stress exceeds 17.21 MPa or the vitreous pressure exceeds 1.01 MPa. Peak stresses were located at the apex of the cornea, the limbus, or the equator depending on the type of projectile impacting the eye. A multivariate correlation analysis revealed that area-normalized kinetic energy was the best single predictor of peak stress and pressure. Additional incorporation of a relative size parameter that relates the projectile area to the area of the eye reduced stress response variability and may be of importance in eye injury prediction. The modeling efforts shed light on the injury response of the eye when subjected to a variety of blunt projectile impacts and further validate the eye model’s ability to predict globe rupture. Results of this study are relevant to the design and regulation of safety systems and equipment to protect against eye injury.

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Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 8

Maximum principal stress versus normalized velocity for different projectiles

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Figure 9

Maximum principal stress versus kinetic energy (logarithmic scale) for different projectiles

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Figure 10

Maximum principal stress versus maximum normalized kinetic energy

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Figure 11

Maximum principal stress versus area-normalized kinetic energy (logarithmic scale) for different projectiles

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Figure 12

Maximum principal stress actual versus predicted plot with 95% confidence curves for the multiple regression model with area-normalized energy and relative size predictor variables

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Figure 1

Geometry for sphere and cylinder projectiles

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Figure 3

Gelatin and orbit surrounding Lagrangian–Eulerian meshes of the eye model. Lagrangian eye mesh (on left) depicting corneoscleral shell, lens, zonules, and ciliary body and Eulerian eye mesh (on right) depicting initially filled volume (darker shading) and initially unfilled volume (lighter shading).

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Figure 2

Projectile mass and diameter comparison

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Figure 4

Experimental rupture versus maximum principal stress in matched computational simulations. The vertical line illustrates the established rupture stress threshold (17.21 MPa).

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Figure 5

Experimental rupture versus pressure in matched computational simulations. The vertical line illustrates the established rupture pressure threshold (1.01 MPa).

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Figure 6

Location of peak stresses in corneoscleral shell for different projectiles

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Figure 7

Principal stress distribution, MPa, at time of peak stress for eight different projectiles. Note the different fringe levels for upper four projectiles versus the lower four projectiles.

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