I'de say pressure doesn't affect them at all.
Or atleast won't affect them any differently then wearing a mask -3atm of air is the same as 3atm of water. just as a kilo of feathers is as heavy as a kilo of lead.
What I would be concered about is the water. If in sea, then salinity might iritate you badly after some while, and might even hurt your eyes, but I don't know about that.
Pollution could also be a problem.
Not being able to see very well should be enough to forget about it I think. It's also a metter of safety. You might not be able to see a thin thread that you've got stuck into for example. Or seeing a Jellyfish (not to mention get burned by one in the eyes

).
If in the pool then I'de say forget about it at all. Chlorine is supposed to kill living cells. I would'nt want that to touch the membrane of my eye (more than the usual exposure once in a while).
My opinion: do you own pipe/fluid goggles for a nose clip.