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Richard Watson, Walter Gray, Randolph D Glickman, Brian J Lund, William Eric Sponsel, Matthew Aaron Reilly, SLOT (Sub Lethal Ocular Trauma); Computational Modeling of Internal Eye Injury due to Primary Blast. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4453.
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© ARVO (1962-2015); The Authors (2016-present)
Ocular trauma has increased from 0.6% to 6% of battlefield injuries over the last 140 years. Recent physical experiments have demonstrated that primary blast can produce significant ocular injury at low levels of overpressure. In most cases, the mechanisms of internal injury are obscured due to the difficulty of imaging inside the eye during the blast event. Alternatively, computational modeling can provide invaluable insight as to the internal dynamics and forces occurring inside the eye under primary blast conditions.
Numerical simulations of primary blast to porcine eyes were used to support a series of in vitro shock tube experiments. Sub-globe rupture levels of blast (overpressures from 50 - 200 kPa) were used in experiments and modeling. Three dimensional Lagrangian Finite Element Analysis (FEA) models were created using material properties from the relevant literature. Internal structures of the eye were modeled in detail to allow visualization of internal dynamics under blast conditions. Experimental and hypothetical blast waveforms with purely positive and purely negative pressure components were applied to give insights as to the relative contributions of each to the observed trauma.
FEA models predicted increasing levels of force, distortion, and strain with increasing blast energy. This is consistent with the experimental finding that likelihood and severity of injury increases with blast energy. Although not visible in the experiments, computational results suggest compression of the peripapillary retina is a potential injury mechanism even at low blast energies (Fig 1).
FEA models confirmed the potential for primary blast ocular injury. The models suggest that different injuries are associated with the different phases of the blast profile. Specifically, posterior segment damage is associated with the positive phase and anterior segment damage (angle recession) is associated with the negative phase (Fig. 2). Computational results correlated with the physical experiments providing insight into injury mechanisms not observable in the experiments. Thus, FEA modeling is an essential supplement to physical experiments.
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