Aviators' Eyeballs
One's Intraocular Pressure is believed to be normal in the range 10 to 20mmHg and this is presumed to be above ambient. Presumably, like our inner ears, this pressure adjusts somehow to cabin pressure.
So what happens during explosive/sudden decompression? Do our eyeballs enlarge and affect vision?
Does anybody know the effects?
Loose rivets
29th Aug 2009, 15:36
The pressure is mainly hydraulic, there should be little or no gas expansion.
The problem for folks that have had LASIC or some such procedure might be significant.
Unpressurized high performance jets would have subjected the pilot's eyes to extreme changes of pressure many times an hour. Can't have been much difficulty with vision for them.
Although it's not really the same, the man that subjected himself to deceleration trials, hit 46g in a forward direction. They removed him from the 'device' with his "Eyes engorged with blood." As far as I know, his vision survived multiple extreme decelerations.
AnthonyGA
31st Aug 2009, 03:10
Gases expand to fill a container, and they continue to exert a pressure in any closed container that is proportional to the volume they occupy. Liquids, on the other hand, are incompressible, and don't exert any pressure on their own—they can only transmit pressure.
A gas bubble in the large intestine exerts pressure on the intestine. As the intestine expands, the pressure exerted by the gas drops, but it never goes to zero, because the compressed state of the gas itself is the source of the pressure. In the eye, though, the liquid (or jelly) that it contains is incompressible, so the only pressure exerted by the liquid is pressure exerted upon it from the outside (such as by the elasticity of the eyeball). The eyeball need only expand ever so slightly to reduce the pressure to zero, since the eyeball is the source of the pressure to begin with. The liquid will not expand.
This is also why a diver coming up from a dive might rupture his lung if he fails to breathe on the way up, but he need not worry about his blood exploding his blood vessels. His lungs contain compressed air that will expand and continue to exert pressure on the lungs, but his bloodstream contains liquid that cannot be compressed, and even a very slight flexing of blood vessels will immediately reduce the pressure within.
Or as another example, consider what happens when you pierce a container filled with air under high pressure, and compare that with piercing a container filled with fluid. The air-filled container will explode outward as the pressure of the compressed air pushes it apart, but the liquid container will simply leak, since liquid is incompressible and cannot hold pressure on its own.