I wear glasses but my prescription is such that I can't buy off the shelf reading glasses or a cheater lens. I weld enough that I bought a pair of prescribed glasses specifically for welding. Can't see sh!t more than six feet away but I see up close really well !!

I generally have my Lincoln helmet set at 9.5 - 10 and I weld mostly 3/16" material in a well lit shop. I have no trouble seeing the weld. Almost all my welding is done right to left with the torch close to vertical to the weld - this means I'm welding towards me, not away - so the weld puddle is always visible. However, once you develop your technique, speed, etc you will pretty much be able to produce welds blindfolded. Really, as long as you have the tip at the right height, the proper angle and your speed is correct and consistent, you only need to worry about where to start and stop - the weld will be fine.

But back to the lighting issue ..
So I sometimes have a problem with spatter flying over my helmet and into my hair and sometimes getting very close to my eyes. To solve this I took an welding jacket and just made a simple hood that I tape to the top of my helmet. So the besides keeping the spatter off my head it also block any light from above or behind.