According to this article i read from Phillips Safety Products, it states that you can safely weld in contacts but advise you to wear ANSI Z87 approved eye protection or if using Oxyacetylene, goggles are the safest option.
As someone who has been welding for 5 years now and wearing my contacts everyday at work, i haven't had any issues with welding in them for 8-10 hours a day.
I however don't wear ANSI Z87 safety glasses under my welding hood due to comfort reasons and being able to see the weld puddle very clearly.
Safety glasses i have found rather cheap and great quality are KleenGuard Mavericks Safety Eye-wear on amazon. These have been my new favorite but im interested in what others are wearing so comment below.
If you wear contacts and are worried how welding in them may effect you i recommend talking with your eye doctor to get a professional opinion.
It's my opinion that welding in contacts is 100% safe but they will not double as safety glasses and you should always be wearing the proper PPEwhen doing any welding and fabrication.
Here are a few safety glasses I personally buy on Amazon ( the links to this post are affiliate links, please read disclosure) :
Kleenguard Maverick Safety Eye Wear