From wiki sunglasses: It is said that the Roman emperor Nero liked to watch gladiator fights through polished gems, likely emeralds. Sunglasses were first used in China in the 12th century or possibly earlier. The "lenses" of these glasses were flat panes of smoky quartz, which offered no corrective powers but did protect the eyes from glare. Contemporary documents describe the use of such glasses by judges in Chinese courts to conceal their facial expressions while questioning witnesses. Compare the representation of "blind Justice" in Western art. James Ayscough began experimenting with tinted lenses in spectacles in the mid-18th century. 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 of his. In the early 1900's, the use of sunglasses started to become more widespread, especially among the pioneering stars of silent movies. But early movie stars did not wear sunglasses as much to avoid being recognized than to protect their eyes from the harshly bright lighting of some early film studios, often taking their sunglasses off only when stepping in front of the camera to shoot a scene. Protection Excessive exposure to ultraviolet radiation (UV) can cause short-term and long-term ocular problems such as photokeratitis, snow blindness, cataracts, pterygium, and various eye cancers.[2] Medical experts often advise the public on the importance of wearing sunglasses to protect the eyes from UV[2]. In the European Union, a CE mark identifies glasses fulfilling quality regulations. In the preparation for solar eclipses, health authorities often warn against looking at the sun through only sunglasses. There is no demonstrated correlation between high prices and increased UV protection. A 1995 study reported that "Expensive brands and polarizing sunglasses do not guarantee optimal UVA protection." [3] The Australian Competition and Consumer Commission has also reported that "[c]onsumers cannot rely on price as an indicator of quality" [1]. One unscientific survey even found a $6.95 pair of generic glasses with slightly better protection than Michael Kors or Salvatore Ferragamo shades [2]. Oakley sunglasses pass the ANSI Z87.1 requirements and offer UV protection Oakley sunglasses pass the ANSI Z87.1 requirements and offer UV protection More recently, High energy visible light (HEV) has been implicated as a cause of age-related macular degeneration[4][5], and some manufacturers design to block it. Sunglasses may be especially important for children, as their ocular lenses are thought to transmit far more HEV light than adults (lenses "yellow" with age). Some sunglasses also pass ANSI Z87.1 requirements for basic impact and high impact protection. These are voluntary standards, so not all sunglasses comply, nor are manufacturers required to comply. In the basic impact test, a 1 in (2.54 cm) steel ball is dropped on the lens from 50 in (127 cm). In the high velocity test, a 1/4 in (6.35mm) steel ball is shot at the lens at 150 ft/s (45.72 m/s). In both tests, no part of the lens can touch the eye.

Can't give you a date they were invented, but i can answer the beneficial portion. I have a cataract only in my left eye. i have surgery planned. this came about, since i drive a police car and most of the left side of my body is exposed to the sun, summer and winter. Wearing sunglasses yearound has really been beneficial to my right eye. my left eye, even with the sunglasses, has been exposed to more sunlight, than my right. the sun shines on my left eye as i park the police car. where i am located, the sun shines and hit my naked left eye and thus the cataract. I know this is a little beyond reasoning, but, accoding to my eye doctor, this is the reason for a cataract in my left eye only. Sunglasses, overall are very beneficial to block the suv rays from the sun.