Risk of Injury to Ocular Tissues from Primary Blast Overpressure Exposure

Abstract

 

Purpose

 

To estimate the risk of injury to ocular tissues following exposure to survivable primary blast overpressure.

 

Methods

 

Fifty-three porcine eyes were included in the study as reported by Sherwood et al. (IOVS 55:1124-1132, 2014). Forty were exposed to primary blast overpressure using a large shock tube while the remainder were treated in an identical manner with the exception of blast exposure. Ultrasound biomicroscopy and histopathology were used to evaluate each eye. A cumulative injury score (CIS; Sherwood et al., IOVS 2014) was assigned for each tissue. Ordinal logistic regression was used to estimate the probability of achieving a given CIS score for each tissue at a given level of blast energy.

 

Results

 

The likelihood and severity of injury to the sclera, angle, choroid, retina, and optic nerve head increased significantly with specific impulse, i.e., the area under the pressure-time trace created by the blast pressure waveform (Fig. 1).

 

Conclusions

 

Primary blast exposure can cause significant ocular injuries even at low blast energy levels. The probability of these injuries approach unity as the specific impulse approaches 1000 Pa-s.  

 

Figure 1: Probability of achieving a cumulative injury score of 1-4 in the (A) sclera, (B) angle, (C) choroid, (D) retina, and (E) optic nerve head. Curves were generated from experimental data wherein ex vivo porcine eyes were exposed to blast overpressure having specific impulse up to 190 Pa-s (300 Pa-s reflected pressure).