Sorry, left it vague for brevity. I'm unable to do all sorts of things without glasses, such as reading or driving. I'm not legally blind, I just have terrible vision. So if I'm in a restaurant trying to see the menu and my mask causes my glasses to fog up there's nothing I can do. I can't see through the fog, and I can't read without glasses.

The majority of visually impaired people who are legally classified as "blind" still have some visual perception and glasses can help maximize that.