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Research Papers

Biomechanical Evaluations of Ocular Injury Risk for Blast Loading

[+] Author and Article Information
Bahram Notghi

Department of Mechanical Engineering,
Johns Hopkins University,
Baltimore, MD 21218
e-mail: notghi@jhu.edu

Rajneesh Bhardwaj

Department of Mechanical Engineering,
Indian Institute of Technology Bombay,
Powai, Mumbai 400076, India

Shantanu Bailoor, Thao D. Nguyen

Department of Mechanical Engineering,
Johns Hopkins University,
Baltimore, MD 21218

Kimberly A. Thompson

Weapons and Materials Research Directorate,
Army Research Laboratory,
Aberdeen Proving Ground, MD 21005

Ashley A. Weaver, Joel D. Stitzel

VT-WFU Center for Injury Biomechanics,
Wake Forest University School of Medicine,
Winston-Salem, NC 27101

1Corresponding author.

Manuscript received December 25, 2016; final manuscript received May 20, 2017; published online June 28, 2017. Assoc. Editor: Barclay Morrison.This work is in part a work of the U.S. Government. ASME disclaims all interest in the U.S. Government's contributions.

J Biomech Eng 139(8), 081010 (Jun 28, 2017) (9 pages) Paper No: BIO-16-1540; doi: 10.1115/1.4037072 History: Received December 25, 2016; Revised May 20, 2017

Ocular trauma is one of the most common types of combat injuries resulting from the exposure of military personnel with improvised explosive devices. The injury mechanism associated with the primary blast wave is poorly understood. We employed a three-dimensional computational model, which included the main internal ocular structures of the eye, spatially varying thickness of the cornea-scleral shell, and nonlinear tissue properties, to calculate the intraocular pressure and stress state of the eye wall and internal ocular structure caused by the blast. The intraocular pressure and stress magnitudes were applied to estimate the injury risk using existing models for blunt impact and blast loading. The simulation results demonstrated that blast loading can induce significant stresses in the different components of the eyes that correlate with observed primary blast injuries in animal studies. Different injury models produced widely different injury risk predictions, which highlights the need for experimental studies evaluating mechanical and functional damage to the ocular structures caused by the blast loading.

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Figures

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Fig. 1

The computational domain including the fluid domain, rigid skull, and the deformable eye. The fluid domain is discretized by a structured grid. The rigid skull is discretized using bilinear triangular surface elements, and the deformable eye is discretized using trilinear hexahedral elements. Initial boundary conditions representing the charge located in front of the face with Lex = 2.5 m standoff distance (Lin) were applied Lin = 1.8 m from charge.

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Fig. 2

Ocular components in exploded view including sclera, limbus, cornea, aqueous humor, lens, ciliary zonule, ciliary muscles, vitreous humor, retina, choroid, lamina cribrosa (LC), prelaminar neural tissue (PLNT), and the surrounding orbital/fatty tissue. Inset: Assembled view of the eye depicting the cornea, limbus, sclera, intraocular, and extraocular tissues.

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Fig. 3

(a) Reconstructed sclera pseudosurface with contours of thickness in (left) temporal and (right) posterior views. Sectioning planes for the current eye model plotted with the sclera model in (b) nasal view. The units are in millimeter.

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Fig. 4

The geometric features of (a) lens, (b) zonules, ciliary body, and (c) the optic nerve head. (a) A fifth-order polynomial was used to define the lens outline from the central axis. (I) The geometric dimensions of the axisymmetric section of the lens including cortex and nucleus. (II) Top view of the lens. (b) (I) A cross section of the revolved finite element mesh of the lens, zonules, and ciliary body. (II) A section of our model showing the connection of the lens, zonules, and ciliary body. The units are in millimeter. (c) The optic nerve head (ONH) consists of the prelaminar tissue, the lamina cribrosa, and the neural tissue. (I) The geometric dimensions of the tissues that make up the ONH are given in detail in Ref. [43]. (II) Cross section of finite element mesh of the ONH.

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Fig. 5

(a) Maximum principal stress in the transverse plane of the orbit, (b) maximum intraocular pressure in the transverse plane of the orbit, and (c) maximum von Misses stress in the transverse plane of the orbit

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Fig. 6

(a) Time-varying maximum intraocular pressure (IOP), (b) high amplitude time-varying maximum principal stress, (c) low amplitude time-varying maximum principal stress, and (d) time-varying maximum von Mises in different ocular structures

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Fig. 7

The probability of occurrence of injuries based on calculated reflected specific impulse for different levels of CIS score level conditions

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Fig. 8

Comparison of the baseline model and the model with uniform thickness for time-varying maximum (left) intraocular pressure, IOP, and (right) sclera principal stress, s1

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Fig. 9

Comparison of time-varying maximum von Mises stress for the baseline model with the model with uniform thickness in sclera, limbus, choroid, and ciliary muscle

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