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R. L. McCally, S. A. D'Anna; Shock Tube Simulation of Primary Ocular Blast Injury in Rabbit. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2995. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Fragments from blast (secondary blast injury) account for ~80 percent of military ocular trauma. However, ocular injuries produced by blast overpressure alone (primary blast injuries) have been observed with greater frequency in modern combat. Although thresholds have been investigated for primary blast injury to the ear, lung, urinary tract, and gastrointestinal system, to our knowledge none have been done for the eye. The purpose of this pilot study was to characterize acute ocular injuries resulting from simulated blast pressure waves at various overpressures.
Six Dutch Belted rabbits were exposed to overpressures ranging from 40 KPa (5.8 PSI) to 114 KPa (16.6 PSI) created by a shock tube. The pulse duration was 4 ms. The anesthetized rabbits were positioned so that the shock wave impinged directly on the left eye. Pre- and post-exposure diagnostics included slit-lamp photographs of the anterior segment, gonioscopy, and fundus photographs.
Epithelial debridement was observed at all pressure levels, but was more severe at higher pressures. At the 114 KPa level, fibrin was observed in the anterior chamber and there was a small hemorrhage in the temporal retina. Because of the curvature of rabbit iris the entire angle could not be observed with the goniometer, but disruptions of the angle were observed even at 40 KPa and were most severe at 114 KPa. The ratio of post-exposure to pre-exposure anterior chamber depth was unchanged for overpressures ≤ 50.1 KPa, but was 1.53 at 64.1 KPa and1.96 at 102 KPa. It was unchanged at 114 KPa suggesting possible sensitivity to orientation.
The results in this study provide the first estimates of thresholds for acute primary blast injury to the eye and indicate a clear need for more extensive investigations. Investigations are also needed to understand injury mechanisms in order to develop injury models. The establishment of injury thresholds and model development will aid in the design of better combat protective gear that will prevent injury from blast pressure in a manner that is complementary to the success of current eye armor in preventing penetrating globe injuries.
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