Pathophysiology of blast-induced ocular trauma with apoptosis in the retina and optic nerve

Blast-induced ocular trauma is a frequent cause of morbidity for survivors of improvised explosive devices. Blast overpressure (BOP) of 120 ± 7 KPa has been shown to cause damage to lungs, brain, and gut in a rat model; however, the effects of BOP on ocular tissues have not been characterized. To elucidate the pathophysiology of blast-induced ocular trauma, ocular tissues from rats subjected to blast were examined for evidence of apoptosis by the detection of activated caspase 3 and TUNEL assay in their ocular tissues.

A compressed air shock tube was used to deliver 120 ± 7 KPa of BOP for duration of 2 msec to the right side of the rats. Rats were then euthanized at specific time points after blast exposure (3 hours, 24 hours, 48 hours). Ocular tissues were processed for immunohistochemistry to detect activated caspase 3 and TUNEL assay. Tissues were evaluated for relative levels of positive signal as compared to nonblast exposed controls.

Activated caspase 3 was detected in the optic nerve, ganglion layer, and inner nuclear layer post blast exposure. At 24 and 48 hours, the inner nuclear layer from the right side had more cells with activated caspase 3. In the optic nerve, the highest levels of activated caspase 3 were detected on the right side at 24 hours post blast.

BOP of 120 ± 7 KPa induces optic neuropathy and retinal damage. In both the optic nerve and retina, caspase 3 was activated in the right and left sides following blast exposure. The results of this study reveal that blast exposure induces apoptosis in both the optic nerve and retinal tissues.