You're wearing regular non-breakable glasses means nothing if a lens flies into
your eye when it is hit with the force of a racquetball. Remember specifically sanction for
racquetball is the key phrase for your racquetball glasses or goggles. Anything
less and you are taking an unnecessary risk with your sight.
Of course, if you like pain and look good wearing an eye patch then playing
racquetball without eye protection is for you.