Carl E. Weiss

Blunt eye trauma: Empirical histopathologic paintball impact thresholds in fresh mounted porcine eyes

PURPOSE Ballistic studies were conducted using gelatin-embedded abattoir-fresh porcine eyes suspended within clear acrylic orbits to discern the energy required to produce specific ocular injuries. Paintball impact provides a robust ballistic model for isolating and quantifying the role of direct blunt force in ocular trauma. METHODS Fifty-nine porcine orbital preparations received direct blows from 0.68 caliber (16-18 mm diameter/3.8 g) paintballs fired at impact velocities ranging from 26 to 97 meters per second (2-13.5 J). Five additional eyes not subjected to ballistic impact were also evaluated as controls. Impact energies were correlated with histopathologic damage. RESULTS Minimum impact energies consistently producing damage in experimental eyes unobserved in control specimens were: 2 joules--posterior lens dislocation, zonulysis, capsular rupture, and choroidal detachment; 3.5 joules--moderate angle recession; 4 joules--anterior lens dislocation; 4.8 joules--peripapillary retinal detachment; 7 joules--severe angle recession, iridodialysis, and cyclodialysis; 7.5 joules--corneal stromal distraction; 9.3 joules--choroidal segmentation; and 10 joules--globe rupture. CONCLUSIONS Impact thresholds correlating traumatic ocular pathology with impact energy followed a positive stepwise progression in severity with impact energies between 2 and 10 joules. Moderate angle recession commensurate with typical clinical traumatic glaucoma was not observed among control eyes, but occurred at relatively low impact energy of 3.5 joules among test eyes. Extensive disruption in and around the angle (iridodialysis/cyclodialysis) consistently occurred at energies >7 joules. Globe rupture required a minimum energy of 10 joules.

Impact Experiments Into Borosilicate Glass at Three Scale Sizes

Abstract : Glass impact experiments were designed at three different scales--0.22-cal, 0.375-cal, and 0.50-cal--named after the diameter of the bullets. Four experimental series were conducted at the three scale sizes: 1) Lexan-only experiments; 2) monoblock glass experiments; 3) single impact bonded glass experiments, and 4) multi-hit experiments. The experiments were conducted to obtain residual velocity as a function of impact (striking) velocity, including sufficient partial penetrations to calculate a V50. The Vs - Vr data were fit to the Lambert equation, Eqn. (5), to obtain another estimate of V50. Eroded lengths of the bullets were also measured. The objective of the experiments was to investigate whether a time dependency exists in glass damage/failure for ballistic experiments, and if so, try to quantify this dependency. No scale effect was observed in experimental results for the Lexan-only experiments. But a variety of scale effects were observed in the glass impact experiments, suggesting that there exists a time dependency to failure that is important within the timeframe of ballistic events.

Measurement of damage velocities in impacts of transparent armor

A series of impact experiments were conducted to examine the response of transparent material to ballistic impact. The experiments consisted of impacting 15 mm of borosilicate glass bonded to 9.5 mm of Lexan. The projectile was a 0.30-cal hard steel bullet designed specifically for the experiments. High-speed imaging of the impact event and post-test analysis quantified damage propagation and the rate of propagation.