When you lose that small screw from your glasses, use a metal wire from a twist tie. Insert through the screw holes, twist and cut off any remaining wire. Tuck away from face side so no sharp points will scratch you. You may have to shred the paper or plastic off first for neatness and a better fit. A paper clip will hold the frame in place until you can repair with a screw.
Add a couple to an emergency pack that you keep in the car, office, or drawer at home for any fast fixes.