Glass lenses? That's an even worse idea, man.
Your mentality and rationale are wrong, but enjoy limited depth perception, blindness or worse.
Also, do you know how fast 400 feet per second is?
That's 270 (two hundred and seventy) MILES per hour. The eyesight you got now is the only eyesight you've got for the rest of your life. Take care of it. I don't want something bad to happen to you, man. Get a cheap pair of goggles from Jungletoy, or a mesh mask, or a paintball mask. They're all less than thirty dollars and will provide adequate protection from the velocities we're talking about.