Dropped, squashed, stretched and bent. Glasses have a tough time and it's always your most expensive pair that seems to break first. Here's how to keep your shades on the road at least until you can have them fixed by a pro.
If a screw comes out... The arms are often held together by screws. To fix these, you will need a tiny screwdriver. Sometimes these turn up as prizes in Christmas crackers, but both electronics shops and opticians sell them. If you have lost the missing screw, you can obtain the correct replacement at the opticians - or remove one from an old pair. As an emergency measure, you can use thin wire and pliers to keep them in use. Push the wire through the hole and wrap it around the inside of the frame several times before twisting the ends together with pliers. Work with the arm in the "open" position, pull the wire tight, and don't try to close the frames.
If the frame becomes loose... Both metal and plastic frames are designed to be reshaped while warm. Heating them gently will soften the material and allow you to bend the arms back. Place them in water the temperature of a hot bath for a minute or two. Remove the frames from the water and bend the arms gently, replacing them in the water to reheat if the frame cools and stiffens. Don't force the arms or you will risk snapping them. Instead, hold each arm lengthwise between the thumbs and forefingers of both your hands and squeeze gently, using a "bouncing" motion and moving your fingers up and down the arm to reshape it gradually.
If a lens falls out... Lenses may be held in a solid plastic frame, in a metal frame held together with a small screw, or secured in a "rimless" frame using a nylon wire that sits in a groove along the edge of the lens. Metal frames can be mended with a screw or, temporarily, with wire. If a plastic frame has not broken, you can snap the lens back into place by pushing it firmly into the frame, usually from the reverse side. Putting a lens back into a rimless frame is trickier. A good tip is to pull the nylon wire around the edge of the lens using a strip of thin, non-stretchy fabric. Put the lens into the top half of the frame then use the fabric to pull the wire around the lens and into the groove.