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W. E. Sponsel, W. Gray, J. D. Walker, D. P. Nicolella, F. W. Scribbick, C. E. Weiss, P. Miller; Histopathologic Blunt Ocular Trauma Impact Thresholds. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4900.
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© ARVO (1962-2015); The Authors (2016-present)
High-speed ballistic studies of gelatin-embedded abattoir-fresh porcine eyes, suspended within clear acrylic orbits, show ocular displacements and deformations remarkably similar to those generated by supercomputer dynamic models that substitute mathematical indices for human ocular structures. Paintball impact has proven to be a particularly robust ballistic model for isolating and quantifying the role of direct blunt force in ocular trauma. The present study evaluates intraocular histopathologic changes accompanying dynamic ocular distortions, using the empirical porcine model, to discern the minimum forces required to produce each of a series of classic ocular injuries associated with blunt trauma. Of particular interest was the force required to produce changes associated with traumatic glaucoma.
34 porcine orbital preparations were submitted to direct blows from 0.68 caliber (16-18 mm diam/3.8 gm) paintballs fired at impact velocities ranging from 85-317 ft/s (2-13.5 Joules). Five control eyes not subjected to ballistic impact were also evaluated. Impact energies were correlated with qualitative histopathologic damage.
Corneal abrasion, minor angle recession and retinal detachment were artifacts observed in control and test specimens. Minimum impact force for changes seen consistently in the experimental eyes but not observed in any control specimens were, in ascending order order of impact force: 2 Joules - posterior lens dislocation/zonulolysis/capsular rupture, choroidal detachment, 3.5 J - moderate angle recession, 4 J - anterior lens dislocation, 4.8 J - peripapillary retinal detachment, 7 J - severe angle recession, iridodialysis, cyclodialysis, 7.5 J - corneal stromal distraction, 9.3 J - Choroidal segmentation, 10 J - globe rupture.
Threshold values correlating specific pathologic consequences of ocular trauma with impact force followed a stepwise progression in relative severity with impact energies between 2 and 10 Joules. Moderate angle recession commensurate with levels seen in traumatic glaucoma was observed at a relatively low impact force level of 3.5 Joules, and not observed among control eyes. Extensive disruption in and around the angle (severe recession, iridodialysis, cyclodialysis) was consistently present in eyes sustaining impact energies >7 Joules, and absent at lower levels. Globe rupture required a minimum force of 10 Joules. These data may assist in development of preventative and interventive measures to mitigate pathologic consequences of blunt trauma and blast injury.
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