Abstract
Purpose: :
To characterize effects of blast-mediated injury on the structure and function of retinal ganglion cells (RGC) and the optic nerve (ON) in order to improve diagnostic and treatment modalities for soldiers exposed to blast-mediated traumatic brain injury (TBI).
Methods: :
Healthy adult C57/Bl6 mice were exposed to a blast wave (137 kPa) using a custom built blast chamber. RGC/ON function and structure were evaluated using the chromatic pupil light reflex (cPLR), pattern electroretinography (pERG) and spectral-domain optical coherence tomography (SD-OCT).
Results: :
Assessment of the cPLR demonstrated a decreased maximum pupil constriction diameter in blast-injured mice (n=20) when using red light stimuli of 630 nm wavelength (Ctrl=1.12 ± 0.05 mm; TBI = 1.38 ± mm; p = 0.0063, Student’s t-test) or blue light stimuli of 480 nm wavelength (Ctrl = 0.56 ± 0.02 mm; TBI = 0.71 ± 0.02 mm; p = 0.0008) 24h after injury. Baseline pupil diameters before illumination were not significantly different between control and blast injured animals (Ctrl = 2.11 ± 0.05 mm; TBI = 2.11 ± 0.04 mm; p = 0.9914). Pattern ERG responses 24h after injury were also significantly decreased compared to pre-recorded values (Pre-rec = 7.17 ± 0.34 µV; Post-TBI = 5.34± 0.64 µV; p < 0.05). Three months following injury a significant thinning of the superior retinal nerve fiber layer was observed in animals with blast-injury compared to controls using SD-OCT (Ctrl = 45+4µm, TBI = 32+1µm; p = 0.009). Histological analysis showed loss of retinal ganglion cells and recipient thalamic neurons.
Conclusions: :
Blast-induced traumatic brain injury is associated with severe functional and structural retina and optic nerve deficits in this experimental mouse model. Utilization of non-invasive functional (cPLR, pERG) and structural (SD-OCT) diagnostic tests may be useful approach for early detection of visual system abnormalities in blast-injured subjects.
Keywords: optic nerve • electroretinography: non-clinical • ganglion cells