Before there were sunglasses:
It is said that the Roman emperor Nero liked to watch gladiator fights with emeralds. These, however, appear to have worked rather like mirrors. Flat panes of smoky quartz which offered no corrective powers but did protect the eyes from glare were used in China in the 12th century or possibly earlier. Contemporary documents describe the use of such crystals by judges in Chinese courts to conceal their facial expressions while questioning witnesses.
James Ayscough began experimenting with tinted lenses in spectacles in the mid-18th century, around 1752. These were not "sunglasses" as such; Ayscough believed blue- or green-tinted glass could correct for specific vision impairments. Protection from the sun's rays was not a concern for him.
In the early 1900s, the use of sunglasses started to become more widespread, especially among the pioneering stars of silent movies. It is commonly believed that this was to avoid recognition by fans, but the real reason was they often had perennially red eyes from the powerful arc lamps that were needed due to the extremely slow speed film stocks used. The stereotype persisted long after improvements in film quality and the introduction of ultraviolet filters had eliminated this problem.
Inexpensive mass-produced sunglasses were introduced to America by Sam Foster in 1929. Foster found a ready market on the beaches of Atlantic City, New Jersey, where he began selling sunglasses under the name Foster Grant from a Woolworth on the Boardwalk.
Polarized sunglasses first became available in 1936, when Edwin H. Land began experimenting with making lenses with his patented Polaroid filter.