I am nearsighted. My vision is sharp from around 8" to about 24" without glasses.
I have three Optivisors: #3, #5 and #10, and have had them for at least 10 years.. I wear them without glasses.
I use the #5 almost exclusively. As I was just a minute ago, and will when I go back to modeling in another few minutes. It's on my head often enough that my neighbors must think I'm a counterfeiter or something.
I've never used the #3. I occasionally use the #10 for close work. It has an irritatingly close depth of field, so it's not an everyday sort of thing.