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Rahul Mandiga, R. Craig Virnelson, Suber S. Huang; Vitreo-retinal Interface Injury After Non-contact Acceleration Impulse With Variable Impulse Time In A Porcine Globe Model. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5342.
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To characterize the amplitude and duration of anterior-posterior (A-P) and lateral vector non-contact acceleration impulse threshold for vitreo-retinal interface (VRI) injury in a vitreous-digested porcine globe model.
Fresh porcine globes were injected with 0.3cc of 0.25% (2.5g/L) Trypsin-EDTA (T-E) (Invitrogen Carlsbad, CA) and incubated for 2 hours. An Endevco 751-10 accelerometer (Sensitivity 10mV/g; Range 550g; 1.2MHz. San Juan Capistrano, CA) was attached to a housing box, which was directly fixed to a pendulum head. Globes were positioned for A-P or lateral vector impact within the pendulum head complex to be shielded from direct impact. The pendulum head was dropped from maximum height to strike a barrier with different foam padding to create an impulse of varied duration. We generated impulses that lasted 15 to 30ms to simulate impulses that cause central nervous system injury. Three eyes were tested with each type of foam in both A-P and lateral vectors. Globes were evaluated by light microscopy for VRI injury.
Table 1 describes the pattern and extent of VRI injury and the amplitude and duration of acceleration impulse for each trial. In the A-P vector, 33% of eyes had VRI injury at a mean impulse of 153.87g (sd=7.27g) over a mean of 16.9ms (sd=0.59ms); 33% at 111.17g (sd=1.17g) over 22.7ms (sd=1.35ms); and 66% at 161.56g (sd=7.77g) over 30.97ms (sd=0.29ms). In the lateral vector, 33% of eyes had VRI injury at 153.4g (sd=7.67g) over 16.9ms (sd=0.44ms); 66% at 109.8g (sd=0.51g) over 22.57ms (sd=1.04ms); and 100% at 158.48g (sd=6.97g) over 30.8ms (sd=0.25ms). A-P injury was localized to 1 to 2 quadrants while lateral injury was present in 3 to 4 quadrants.
With acceleration impulses lasting 15 to 30ms in both the A-P and lateral vectors, the threshold for VRI injury appears to be near the range of 110 and 160g. Compared to our previously described threshold between 300 and 500g for 4.5ms impulses, our data suggests that impulse time is an important variable in the characterization of the VRI injury threshold.
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