What are you going to use the torch for? Jewelers use oxy-fuel
(generally propane or natural gas) torches and I never met one who used
dark glasses except for melting and for platinum work. For brazing,
silver and gold soldering, etc. on small items, most feel it's not
needed. I don't use shaded lenses except for platinum -- when I'm
melting, I just don't stare at the crucible. For platinum, it's
essential, though, as the stuff gets white-hot. For larger brazing
work, some use shades, some don't. I don't, though I only braze larger
stuff infrequently. The oxy-propane flame is nowhere near as bright
and radiant as oxy-acetylene, so it mostly depends on how hot the work
is getting, and how large the radiant area is. (and how close you are
to it, of course).