vbEffects of repetitive low-level blast exposure on visual systems and ocular structures

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). The Cadre group had a reduced ECD (right eye: Cadre 2,478 cells/mm(2) vs Control 2,808 cells/mm(2), p = 0.02; left eye: Cadre 2,562 cells/mm(2) vs Control 2,892 cells/mm(2), p = 0.03). These results suggest that even low-level primary blast has the potential to produce occult eye injury.