My post was more directed at the various accounts of bad experience in the field by fellow posters. I was trying to illustrate that a lot of the common problems faced by bespectacled soldiers in the field can be solved by simple preventative action.
Stuff like specs fogging in the rain, lens becoming filthy, specs keeps slipping, specs fogging when discharging weapon, breaking glasses outfield, specs getting run over, glasses bent out of shape ... These are all situations that will repeat themselves whether in peace time training or wartime conditions. If you can solve them in peacetime, you can solve them in wartime ... until you run out of anti-fog
The only situation I can see as very different will be the concussive force of explosions and the increased amount of debris you will come into contact with.
Speaking without experience of a wartime environment, I can only guess that it again shouldn't be too much of a problem for most military vocations ... a sturdy pair of (butt-ugly) plastic specs with Polycarbonate lenses, good anti-fog and retaining strap should be fairly proof against most events that don't rip your head off. I've used this combination for some very rugged (and wet) activities without problems.
Combat goggles are IMHO, nothing more than mil-spec workshop safety goggles. Their primary role is not to provide indestructable corrective eyewear but to protect the "Optical Sights Mk1" from debris on the battlefield. It'd be good to have but is not entirely necessary ... also, you CAN wear goggles over specs (do that all the time skiing)
I'm not trying to say that problems do not exist, just that they are not as bad as it's being made out to be. Soldiers will break/loss their corrective eyewear somehow and will be less effective when that happens. However, I feel that with proper habits, the problem can be minimized ... as an example, ever notice how some people are always losing their handphones/wallets but some don't? It all boils down to habits and attitudes.
Oh .... have I mentioned optical sights?