Training is different from real combat. Did you ever get blood,
mud, debris, from hits and near misses from bullets , shrapnel
& explosive detonation splattered on your glasses when you are
sweating profusely, tearing ( from smoke and haze ) & deaf when
your heart is racing at 100 mph in a shooting war ? I have not, but
I guess it will have a marked effect on my glasses when in the
combat zone.