What Do You Know About Eyeglasses?

Eyeglasses, defined in Wikipedia, are frames bearing lenses worn in front of the eyes. They are formerly used for vision correction; later for eye protection, either from foreign matter or from harmful rays. In fact, they can be a major part of person image and expression as well.

Eyeglasses are thought to be one of the most important invention of mankind history, because without them, scientists may not be able to do precision researches and bring so many discoveries to us; without them, we ordinary people with eyesight problems will never observe the beautiful world around us clearly.

Since eyeglasses are so important to us, what do you know about them?

Eyeglasses emerge earlier than most of us imagine. The first recorded use of corrective lenses may have taken place around 1^st Century AD in Rome, while the first pair of wearable eyeglasses was invented around 1284 in Italy by Salvino D'Armate. Since then, eyeglasses began their evolution, from those without legs to with legs; from those with glass lenses to high index plastic lenses; from those plastic frames to titanium frames, etc..

Then with different requirements of eyeglasses of different people, diverse types of eyeglasses are then invented.

Corrective glasses: the original corrective glasses are used to correct refractive errors of the eye--myopia, hyperopia or astigmatism, etc.. This should the most common type for people in their daily lives.

Safety glasses: they are mostly used by athletes or sports lovers, helping them prevent foreign bodies entering eyes; what's more, for the fact that there is a greater chance for this kind of glasses to get broken and debris may fly into eyes, safety glasses are usually made with shatter-resistant plastic lenses.

Sunglasses: sunglasses provide protection against harmful rays from the sun, so as to reduce or stop the possibility of the emergence of kinds of eye disease. Additionally, nowadays sunglasses can be of both prescription or non-prescription, that is to say, if you are a person with eyesight problems who has to wear corrective glasses, you can also wear prescription sunglasses which both prevent harmful rays and provide a clear vision.

Presbyopia glasses: they include bifocals, trifocals and progressive lenses. The first two lenses are the traditional ones which have only two or three distinct horizontal viewing area, which are easily to make the wearers dizzy for the sharp transition between the focal points. Unlike the two, the last lenses give a smooth transition, providing the wearers a comfortable feeling.

3D glasses: they are specially designed for people to watch 3D movies. Due to the illusion of three dimensions on a two dimensional surface, 3D glasses can offer each eye with different visual information, making the image more real.

Of course there are many other glasses for different usages, for example glasses for watching the solar eclipse.

As for eyeglass styles, they are of a great variety, ranging from rimless glasses to boxy glasses. At present the most in style is those with thick, black and boxy or round frames, in a kind of restoring ancient way. In street, if you keep an eye on the passersby, you will find a lot of them wearing thick boxy or round glasses of different colors, and some of them even just wear glass frames without lenses, just for fashion.