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Bahram Notghi, Rajneesh Bhardwaj, Thao D Nguyen; Biomechanical evaluations of injury risk for blast loading. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6396.
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© ARVO (1962-2015); The Authors (2016-present)
The mechanisms of primary blast injury and the effectiveness of eye armor in preventing primary blast injuries are not well understood. The objective of this work was to develop an experimentally validated computational model of the human eye to evaluate: 1) the stresses and deformations in the internal structures of the eye caused by the propagation and reflections of the blast wave, and 2) to evaluate the effect of current spectacle and goggle designs on reducing the blast overpressure.
We developed a computational model to simulate the propagation of the blast wave and the interaction of the blast wave with a deforming tissues. The model includes detailed descriptions of the facial features of an average 21 year old male, the internal ocular structures, spatially varying thickness and anisotropic properties of the cornea and sclera. We applied the model to evaluate the intraocular pressure and stresses in the tissue structures caused by the blast wave and evaluate the probability risk of injury based on experimental data for blunt impact available in the literature. In addition, we evaluated the effect of current eye armor design in reducing the blast overpressure loading on the eye.
The von Mises stresses caused by tissue shear were largest in the scleral wall at the site of muscle attachments. In addition, the maximum principal stress and maximum von Mises stress in sclera, choroid, retina, and ciliary zonlues showed the possibility of internal scleral delamination, chorioretinal detachments, and lens dislocation. For a 2kg TNT blast at a standoff distance of 2.5 meters, we evaluated a 5% risk of Corneal Abrasions and 0.2% risk of Hyphema based on the maximum intraocular pressure. Spectacles and goggles reduced the maximum over pressure by 51% and 70% respectively for a 6.4 kg TNT blast at 3.81 meters compared to the unprotected eye. However, the goggles trapped the underwash of the blast wave against the eye and resulted in a higher blast overpressure at 0.2 ms after the peak pressure than for the unprotected eye.
The stress analyses in our study correlate with the observed primary blast injuries in animal and cadaveric tissue studies, including retinal and scleral delamination, and lens detachment. The blast wave loading may generated significant risk of Corneal Abrasions and Hyphema. However, blast specific injury experiments are needed to more accurately evaluate the injury risk.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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