Features

• A central bridge rests the spectacles frame on the nose. The lenses, usually made of glass or plastic, are supported by the rims, which extend on either side of the face to fit over the ears.
  
  

Function

• Spectacles function to correct vision by converging or diverging rays of light. A concave lens corrects short sight, a convex lens corrects long sight and a cylindrical lens corrects astigmatism.
  
  

History

• The earliest evidence of spectacles dates from 500 BC in Egypt. However, the word "spectacle" is attributed to a Dominican friar named Salcino de Armato, circa 1317 AD. The concept remained relatively the same until Benjamin Franklin invented the bifocal lens in 1784.