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J.C. Boak, C. Lau, A.J. Bellezza, A. Saari, P.A. Cripton; Ocular Injury Tolerance to Projectile Impacts During Motor Vehicle Collisions . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5033.
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Purpose: Injury due to small projectiles contacting the eye at high velocity can be devastating because of potential loss of vision. Ocular injury tolerance data can aid automotive design by recommending limits on the allowable speed, mass, and shape of projectiles associated with airbag deployment or vehicle damage during motor vehicle collisions. Our objective was to synthesize the available eye injury tolerance literature to identify any gaps in eye tolerance data that could be critical for automotive safety design. Methods: STAPP Car Crash Conference Proceedings and Pubmed databases were searched via keyword, topic, and related papers. Special attention was paid to corneal and scleral injuries as these appear to be the minimum threshold for vision–threatening eye injury due to projectile impact. Results: Impacting the eye with projectiles of different size, shape, mass and speed result in different injury patterns and different minimum injury thresholds. Kinetic energy and momentum are projectile parameters commonly presented as experimental injury criteria for the eye. Foam particles with momentum between 7130 and 39,890 mg*m/s caused corneal abrasions ranging from 10% to 75% of corneal surface area. Sharp projectiles with tip angles between 30 and 45 degrees penetrated the cornea when traveling with 10 to 90 mg*m/s of momentum. Metal BB's can cause scleral globe rupture when fired at the eye with at least 22,400 mg*m/s of momentum or 0.67 J of kinetic energy. Blunt metal projectiles with a diameter between 12.5 mm and 4.5 mm were found to rupture the sclera when impacting with more than 2.08 J of kinetic energy. With increasing diameter, projectiles require more energy to rupture the sclera. Conclusions: Neither kinetic energy nor momentum alone represent a sufficient injury tolerance criterion because different injuries of different severity can be caused by two impacts with the same energy or momentum due to projectile shape parameters such as sharpness. Therefore in order to incorporate ocular mechanical deformation effects, we conclude that ocular injury tolerance should additionally be quantified by the globe strain and strain rate. A new experimental study is needed to assess the relationship between mass, speed, size, shape and the type of injury caused when projectiles impact the eye. The parameters should span the gap between the sharp and blunt projectiles previously studied. Eye response should include mechanical loading parameters such as globe and cornea local stresses and strains.
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