They usually carry reading glasses up to about +3. . . . and up until the 1950s, some even carried some generic distance glasses with minus diopters. If you have more complicated eye sight problems such as astigmatism, then an over-the-counter set of glasses is not going to be much help.
Reading glasses sold at drug stores are not prescription glasses. I should have used that term. They are not the same:
https://www.aclens.com/Content/Display/161
The bank teller in the TZ episode had horrible eyesight and I doubt that cheap wallgreen glasses would have helped. He also would have had to walk over the rubble nearly blind to find a store that was not vaporized by the blast.