Effects of repetitive low-level blast exposure on visual system and ocular structures

Abstract

Abstract-The purpose of this study was to determine whether repetitive exposure to low-level blasts during military breacher training produces acute and cumulative damage to the ocular tissues or visual system. The effects of low-level blast exposure on high-contrast visual acuity, contrast sensitivity, oculomotor function, color vision, visual field (VF), pupillary light reflex, corneal endothelial cell density (ECD), macular thickness, retinal nerve fiber layer thickness, and cup-to-disc ratio were assessed using a battery of standard clinical ophthalmic tests administered 10 times over a 2-year period. Data from nine male breacher instructors (Cadre) were compared with data from four male breacher engineers (Control). The Cadre group showed higher vertical deviation at near than the Control group over time. The VF mean deviation on the left eye tended to be worse in the Cadre group throughout the study, suggesting a decrease in VF sensitivity (Cadre: -0.20 +/-0.15 dB; Control: 1.05 +/-0.15 dB; p = 0.03). , p = 0.03). These results suggest that even low-level primary blast has the potential to produce occult eye injury.

Repeat low-level blast exposure increases transient receptor potential vanilloid 1 (TRPV1) and endothelin-1 (ET-1) expression in the trigeminal ganglion

“…Repeated exposure to low-level blast is a characteristic of a few select occupations, to include specialized military and law enforcement units [ 40 ]. Specifically, with regard to military breacher training, personnel are typically exposed to 500–600 low-level blasts per year during their two to three training program [ 41 ]. Consequently, the polytrauma associated with blast injuries during military training and operations present serious challenges with respect to clinical assessments and rehabilitation efforts.…”

“…Blast injuries to sensory systems, to include ocular and auditory, are among the most significant concerns of healthcare providers due to their high prevalence over the past few decades. In line with these concerns, recent literature has highlighted the negative effects of blast on visual and auditory function [ 9 , 41 – 43 ] and provided additional insight into the pathophysiology of blast. The findings presented herein, provide further evidence of the effects of blast, namely on pain and inflammatory processes.…”

Development of a new militarily-relevant whole-body low-intensity blast model for mild and subconcussive traumatic brain injury: Examination of acute neurological and multi-organ pathological outcomes

“…To examine appropriate driver pressure, various combinations of 0.003" and 0.005" polyethylene sheets were assessed in combination with various driver pressure thresholds, until the correct combinations were found to reliably reproduce waves corresponding to 6, 8, 10 and 15 psi, based in literature representations of mild BINT. The Canadian Army and US Army Doctrines specify exposure limits of 3 and 4 psi (respectively) for overpressure during range training 47,48 , however helmet-mounted sensors have detected frequent repetitive exposures at or above 6 psi [49][50][51] . There is now evidence that repetitive subconcussive blast events may elicit the same symptoms as those seen for mTBI, particularly in the operational scenario in which repeated blasts are experienced within a short .…”

Occupational Risk of Low-Level Blast Exposure and TBI-Related Medical Diagnoses: A Population-Based Epidemiological Investigation (2005–2015)

“…However, previous research on LLB is limited in several ways. Studies on human participants have relied on very small samples (typically fewer than 40 participants in military and law enforcement samples) [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Additionally, these studies often investigated self-reported subclinical symptoms, which may not correspond to clinically diagnosable injuries [ 23 ].…”