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"Johnny Poppers": a cause of serious ocular injury
1Department of Ophthalmology, Southern General Hospital NHS Trust, Glasgow.
Aims/Background:
The causes of blunt ocular trauma are many and diverse. We present two cases of ocular injury caused by an unusual form of weapon called a "Johnny Popper". There follows a theoretical and experimental evaluation of the velocity of the projectiles fired by this device.
Methods:
A Johnny Popper was constructed under expert guidance. The elastic properties of the device were measured and this allowed calculation of a theoretical exit velocity of the projectiles fired. The weapon was subsequently fired under test conditions which permitted the exit velocity of the projectiles fired to be measured directly.
Results:
The theoretical velocity of the projectiles was calculated as 80 ms-1 and the experimentally measured velocity was 57 ms-1.
Conclusions:
Johnny Poppers are a previously undescribed and unique form of home made weapon. They are intended for playful mischief, but have the potential to cause serious ocular trauma.