I got a pair of gas welding specs with my plasma but the elastic snapped so I switched to using my Optrel welding mask in grinding mode (stops the screen from darkening for 10 mins. when grinding) - it's a perfect shade 4.
My mention referred to gas welding goggles and not other glasses. Gas welding goggles have a different lenses rating (GWF) to those used for electric arc applications (EW). I wouldn't use gas welding goggles with my MIG welder!!
I wouldn't weld with them instead of a welding mask, But any sort of lens infront of the eye protects the direct UV. Which is why a lot of work shops insist on all the lads wearing safety glasses. You will still get startled by the bright flash but will not give the arc eye symptoms as it lets very little if any UV through.