I used to work in a cast iron shop (Rockwell) and I would say that I was probably in the ER between 6-12 times for metal in the eye. The bad thing was that everyone used airhoses to blow the machines off, so there was cast iron particles going everywhere. When I became a Tool & Die Maker at my last place, we worked more in aluminum, and I have had that in my eye on a couple of occasions. The bad thing was that I had prescription safety glasses, but they were of a piss poor design. I finally found a pair that I liked and have about a half a dozen of them scattered around the garage. They wrap around more like goggles. (Harley Davidson safety glasses) They fit very well and you don't see any of the frame while wearing them. BUT....you can't beat safety goggles. Something that seals completely around your eyes. Of all the time I had metal in my eye, it was from bouncing off the back of my safety glasses into my eye. Goggles would totally prevent that.
One of the very worse things I had happen was when I was framing out some cabinets. We were building a 2x4 framework and I was driving in some 16D's with a hammer. On one nail, the hammer went off the side, flipped the nail, and just like in slow motion I saw the nail spinning towards me. I didn't have glasses on and it smacked me right square in the eye. Luckily I had my eyes shut, and I was hit by the head of the nail square in the eye. It created some massive bruising, and today I have scar tissue in that eye.