Eye glasses are used to correct vision problems and consist of a frame and lenses. The lenses are the most important part as they are what correct your vision. Besides vision correction lenses can also protect your eyes from harmful UV radiation. Eyeglasses have evolved tremendously over the years and historical eyeglasses include the pince-nez, monocle, scissors glasses and lorgnette. Much more modern glasses will have padding at the temples and nose for comfort.
Lens can also be made of CR-39, polycarbonate and plastic besides the more traditional glass. These other materials are advatantageous as they are more difficult to break, weight less, better transmit visible light and absorb more UV light. Synthetic materials also can be shaped in different forms that can correct vision abnormalities. Some of the newest plastic used for lenses, called izon, can even provide vision correction for higher eye order aberrations.
The newest materials for eye glasses are scratch resistant and most will have hydrophobic coatings and anti-reflective coatings. The hydrophobic coating makes the lenses very easy to clean and the anti-reflective coating reduces glare and can help improve your night vision. The most popular type of plastic lenses on eyeglasses are CR-39 because these lens are very light, have a low transparency of UV and infrared light, and are very scratch resistant.
Corrective eye glasses are used to correct refractive errors of the eye. In essence the eyeglasses corrects your vision by modifying the length of the lens to correct for nearsightedness, astigmatism, or farsightedness. It is possible to obtain over the counter reading glasses that run from +1. 00 to +3. 25. However for negative strength glasses for those that cannot see far away a prescription is needed.
Eyeglasses are also used as safety measures for eye protection. Safety eyeglasses are made of shatter proof plastic that protects your eye. This protection is needed when the chance of flying debris could damage your eye. Safety glasses are worn in many industries and are needed anytime you are working with chemicals. Safety eyeglasses may have additional shielding at the temples and you can also purchase prescription safety glasses.
Eyeglasses can also have several different purposes. There are safety glasses that are used by many different industries to protect the eye from any flying debris or chemicals. Safety glasses are shatter resistant and can have temple shields to protect your eyes from all directions. Safety glasses are required in all laboratories as well as industries that use heavy equipment such as limber, the food industry and many more.
Sunglasses have many different colored lens. Yellow lenses can be used to improve your depth perception and color contrast. Brown lenses tend to cause color distortion and are used by golfers. Sunglasses that are green, purple or blue do not enhance your vision at all. Many times sunglasses are only worn for aesthetic reasons as a person may want to hide their eyes. In this case mirror shades are very popular.
Other types of eyeglasses include 3D glasses that create a three dimensional illusion, reading glasses that are general for very mild cases and can be purchased over the counter, bifocals which have two focus lenses, general for near sight at the bottom and far sight on the top, trifocals have three different lenses for multiple focus and progressive eyeglasses that are multi focus but do not have any lines and have a smooth transition between different focal lenses.
