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W. E. Sponsel, W. Gray, A. Bonivtch, C. E. Weiss, F. W. Scribbick, J. D. Walker, D. P. Nicolella; Investigation of Paintball Ocular Trauma: A Path Towards Safer Paintballs. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5485.
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Injuries due to paintball impact are a growing source of severe ocular trauma. One realistic preventative goal is to design safer paintballs that break more readily on contact, producing less globe displacement. To achieve this requires a fundamental understanding of the dynamic biomechanical behavior of the eye within the orbit (stress, strain, and pressure responses) to varying paintball impact conditions (material, mass, impact angle, and velocity), and details of resulting trauma.
To validate the finite element models and determine failure and injury criteria for the eye, repetitive in vitro testing was conducted. Instrumented porcine eyes suspended in gel-filled transparent orbits were impacted with paintballs at varying velocities and impact angles. The clear acrylic surrogate orbits afforded a realistic representation of human orbit geometry and boundary conditions, allowing for dual-angle high-speed video imaging. Paintball/ocular impact and dynamic mechanical responses were studied through finite element analysis. The physics-based numerical codes CTH and LS-DYNA were utilized while incorporating robust geometric and constitutive models of the eye and orbit. Following impact, the eyes were subjected to detailed histopathology. The type, location, and extent of trauma was correlated to the impact conditions. Resulting associations were then used in conjunction with the finite element models to predict injury, allowing for the formulation of alternative paintball designs.
Competitive (C) and amateur (A) grade 2.6mg paintballs delivered at velocities 25-90m/s with kinetic energies of 4.5-13J, produced intraorbital posterior globe displacements of 5.3-17.6mm, accompanied by AP globe compressions of 3.0-5.8mm. Ocular deformation was comparable with both grades of paintball, but globe displacement was 37% greater with the more rigid A-grade paintballs, which produced more severe ocular injury (lens subluxation, angle recession, retinal detachment, etc).
Surface scoring and other shell alterations may enhance the superior safety profile of existing C-grade paintballs. High-speed video provides dramatic, memorable images that may help increase public awareness of the profound risks posed by these recreational projectiles.
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