Crack

• Any slight crack in any part of the eyeglasses indicates they are broken. The crack may be so small that, ironically, you need eyeglasses to see it. Although a small crack need not be a major problem, it's probably as well to stop using the eyeglasses and get a new pair. This is especially important if the crack is on one of the lenses.
  
  

Missing Parts

• Eyeglasses consist of only a few parts, but if any part is missing, it's a sure sign that the eyeglasses are broken. Sometimes, a nose pad, one of the small parts that cushions the glasses against the nose, falls off and you might not even notice. Another fairly common missing part is the temple cover, the plastic sleeve that fits over the end of the earpiece. If you can find the missing part, you may be able to refit it.
  
  

Screw Loose

• If your eyeglasses fall off the end of your nose, it might indicate a hinge screw has worked loose, causing one of the temples, the side arms of the eyeglasses, to slip over the top of your ear, thus causing the eyeglasses to fall off. Hinge screws are notoriously tiny and almost impossible to find. Even if you do find it, you'll need a very small eyeglass or watch screwdriver to screw it back in place.
  
  

Other Signs

• If you inadvertently drop your eyeglasses from a great height onto a hard surface, like concrete, they will probably sustain some damage. Similarly, if you accidentally sit on your eyeglasses and hear a cracking sound, this is an indication your eyeglasses are broken. You might be able to take your eyeglasses to an optician's for repair, or you might need to buy a new pair.