With the help of an inexpensive eyeglass repair kit, you can perform minor repairs on eyeglass frames. The kits are sold at drugstores and hardware stores.
Examine the cause of the problem with a magnifying glass. Is the hinge stretched out? Is the screw loose or missing? Did the hinge break off?
If the hinge is stretched out, cover the tips of a pair of pliers with masking or duct tape to avoid scratching the frames and then use the pliers to bend the hinge gently back into place. Or slide an orthodontic rubber band (available from dentists) or a small rubber ring (an eyeglass repair kit may include this) over the loose hinge to hold it in place.
If the screw is loose, tighten it with a tiny screwdriver from the eyeglass repair kit. The tip of a paring knife will serve as a screwdriver in a pinch.
If the screw is lost, replace it with one of the screws from the kit, or slip a miniature safety pin into the screw hole and close it. If the repair kit's screw does not fit into the hole, do not force it, as that might strip the threads inside the frame.
Dab a tiny bit of clear nail polish on the hinge screw once you've tightened it to hold the screw in place. Let dry.
If the metal hinge has broken off the frame, wash both surfaces and scrape away any paint or old glue. Then use a toothpick to dab fast-bonding glue to the break. Hold the pieces in place for 60 seconds to allow the glue to dry.
If the earpiece keeps slipping off the frame or has broken off, re-adhere it with fast-bonding glue. If you get the glue on your skin, wipe it off with acetone-based nail-polish remover.