Q. I noticed that when wearing a corona mask, it causes my glasses to fog up and I constantly have to remove my glasses to clean them. May I nevertheless wear the mask on Shabbos? 
A. Horav Shlomo Miller’s Shlit’a opinion is that since the mask is essential and we do not have a proper reshus horabim in most cities only a karmelis, there is, in need room to be lenient.
You may change to another type of mask or face cover that does not cause the fogging effect, or line the bottom of the glasses before Shabbos with tape.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a.