I've heard a lot of people say they're not correctional, but I've never seen an official source on that.
I'm skeptical that he'd wear the same pair of glasses literally all the time in his day to day life if he didn't need them. I doubt that he's Velma without his glasses, but he probably still does need them.
Until I get an official confirmation from somewhere that that's not that case, I'm just going to assume that "his vision is fine and he just wears them for fashion" is just something that everybody assumes because everyone else assumes it.