There have been a few times when wearing glasses has probably saved my vision.
One that comes to mind easily was waiting for a pickup truck to pass by so I could cross the street. A nice-sized pebble whacked one of my lenses almost straight-on.That's the kind of thing where you don't even have time to blink, not that a thin flap of skin would do a whole heck of a lot against a sharp, speeding stone.
Eyes suck - they are incredibly useful, they are (currently) irreplaceable, and they are also incredibly easy to damage.
I've noticed that professional lawn guys will ALWAYS stop mowing or weed eating when you're around. Hell, I even do the same if there are folks coming on the sidewalk. I have protection, they don't.
I too have been whacked smack dab in the eye (on the glasses, right at my eyeball) with protection and was thankful I had it. I thought I was pretty careful, guess not enough when I was deep in the bush.
