Intravitereal Pressure (IVP) During Primary Blast Exposure in an in-situ Porcine Cadaver Model

Abstract

Purpose: Previous research has shown that primary blast exposure is capable of causing physical and pathophysiological damage to the eye. However, a large gap still exists in the understanding of physical mechanisms and progression of blast-induced ocular trauma. Increasing intravitreal pressure (IVP) during high speed projectile impacts correlates to eye injury risk. We therefore hypothesize that increased IVP resulting from primary blast exposure also correlates to eye injury risk. The purpose of our current research is to dynamically measure the IVP of in-situ porcine eyes during experimental blast exposure and assess ocular injuries sustained in order to more fully understand the effect of blast overpressure on the eye.

Methods: A compressed air shock tube was used to deliver blast waves with peak overpressures of 97.4±4.1, 163.3±6.5 and 208.5 ±19.8 kPa to pig cadavers. Duration of the positive pressure peak ranged from 3.2 to 3.9 ms. Exposures were conducted with the pig cadavers facing directly into the incident blast wave. Pig carcases were obtained via a tissue-sharing agreement, and were exposed within 2 hours after euthanasia. The IVP was dynamically measured during the exposure using a pressure transducer embedded in the vitreous of right eye. After ophthalmological examination, the left eye was collected and processed for histological evaluation after all experiments.

Results: Retinal detachment was observed close to optic nerve head and ciliary body for 208.5 ±19.8 kPa of blast overpressure (BOP) exposures. Tissues from unexposed control cadavers as well as pigs receiving exposures to 97.4±4.1 and 163.3±6.5 kPa BOP showed negative or mild retinal detachment. The IVP exhibited a complex structure due to reflections and refractions within the ocular tissues that changed in character with increasing BOP.

Conclusions: We have collected data in the intravitreal pressure and corresponding damage to the eye for various levels of blast wave exposure using a pig cadaver model. This data will be used to validate computer models of the interaction of blast waves with the eye.