Mechanism and Emergency Management of Blast Eye/Orbital Injuries

Sabri T Shuker

Disclosures

Expert Rev Ophthalmol. 2008;3(2):229-246. 

In This Article

Experimental Analysis of Dynamic Stress/Strain Properties of Eye Rupture

Globe rupture may occur when a primary wave impacts the orbit, causing anterior–posterior compression of the globe and raising intraocular pressure to a point that the sclera tears. A rupture also may occur when the integrity of the outer membranes of the eye is disrupted by a blast overpressure wave, penetrating shell fragment, sand particles or dirt that cause abrasion or deep laceration which weaken the eye wall, as stated on globe rupture by Robson (2007).[104] Propelling of the body against walls or objects or otherwise may lead to eye/orbital injuries when it is hit by protruded blunt or penetrating object as a tertiary blast effect.[23]

Biophysics explains the pathophysiology of why secondary blast explosively propelled fragments inflict eye/orbital injury as they penetrate or rupture the eyeball. According to the supercomputer simulation study by Uchio et al. (1999),[24] the sizes of missile above which corneal rupture occurred at velocities of 30 and 60 m/s were 1.95 and 0.82 mm, respectively. However, the missile sizes causing sclera rupture were 0.95 and 0.75 mm, at velocities of 30 and 60 m/s.

As a correlate, another pressure system study was built to examine the static and dynamic properties of healthy postmortem human eye rupture and pressures needed. This will help us to determine the primary blast wave front stress force that is required to inflict eye/orbital injury and, conversely, the protection needed to prevent it. Voorhies (2003), in her thesis submitted to the Faculty of the Virginia Polytechnic, found that maximum rupture stress for the somewhat static tests was found to be 11.17 MPa for human tissue;[105] whereas, stress for the dynamic tests were found to be 30.18 MPa. Maximum rupture stress results correlate well with static material properties used in published research, such as 9.4 MPa and dynamic properties of 23 MPa.[25,105]

Eye ruptures in the region of the limbus are often circumferentially oriented, and ruptures at the equator are often zonally oriented. This reveals the predominant direction of collagen fibers in those two regions, which is circumferential at the limbus and meridional at the equator.[26–28]

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