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R. Mandiga, T. L. Gosen, A. A. Polinkovsky, A. D. Rolin, S. S. Huang; Vitreo-Retinal Interface Injury After Lateral Deceleration Impulse. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3188.
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To identify physical parameters for deceleration impulse in non-contact lateral impact injury to porcine and bovine globes as a physical model of vitreo-retinal interface (VRI) injury.
Impact parameters were measured by an accelerometer on a 1.65m track. Final velocity was calculated using the equation Vo=(L*sinθ*2*g)1/2 where L=length of the track, g=acceleration due to gravity (9.8m/s2) and θ=angle of incline of the track. Linear deceleration was assumed and calculated by dividing the final velocity for a given angle by the measured time of impact. Bovine and porcine globes were obtained within 24 hours of enucleation. Each test globe was anchored at rectus muscle insertions to a nylon with cyanoacrylate and positioned 90 degrees to the deceleration vector inside a foam-padded cart. The cart was accelerated at 45 and 90 degrees. Each globe was inspected for gross VRI injury.
Average time of impact was 4.36ms (r= 2.9-5.14ms n=33). Calculated final velocity and deceleration was 4.78m/s (10.69mph); 111.91g at θ=45 degrees and 5.69m/s(12.73mph); 133.09g at θ=90 degrees. Allowing for 30% mechanical inefficiency, the calculated final velocity and deceleration was 3.35m/s (7.49mph); 113.85g at θ=45 degrees and 3.98m/s (8.90mph); 135.40g at θ=90 degrees. At 90 degrees, pathology was seen in 75% bovine and 100% porcine eyes. Injuries included RPE pigment changes, retinal tear, retinal dialysis, retinal detachment, and/or avulsion of the vitreous base. At 45 degrees, 33% bovine globes had pathology.
The physiologic effects of lateral impact in the eye, such as in kickboxing, assault, and side impact MVA, are not well understood or characterized. In our model, deceleration impulse was over 300% the value reported to cause irreparable brain injury. Less lateral impact retinal pathology was observed in bovine eyes at lower deceleration impulse. Because porcine eyes more closely resemble human eyes, the pathology noted in porcine eyes may have clinical implications. These preliminary results lead us to believe there is a definable threshold for VRI injury.
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