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.
Synthetic eyeglasses can also filter out UV light to protect your eyes, are very durable and can transmit visible light much better the glass eyeglasses. Some of the newest materials for eyeglasses, one being izon, can even correct higher eye aberrations which could be difficult to fix.
Today glasses are all scratch resistant and will have several different types of protective coatings. The most common coatings include scratch coatings and anti-reflective coatings. The anti-reflective coating works very well for night vision as it reduces glare. There are hydrophobic coatings that can be used that repel dirt and water so that you can easily clean your glasses. All plastic lenses will have coatings as they are very popular as they are light in weight, protect against UV light and are scratch resistant.
Eyeglasses are able to correct your vision problems as the lense modifies the length the light hits your eyes. This modification of the lens so that the lens in your eye and the eyeglasses lens will allow you to see properly. It is possible to use eyeglasses for farsight, astigmatism and nearsight. Farsighted eyeglasses or reading glasses can be purchased over the counter if you only need a slight vision correction. Those that are nearsighted and have astigmatism will need to have an eye exam and prescription eyeglasses.
Sunglasses can be obtained as prescription or non-prescription lenses. The main purpose of sunglasses is to protect your eyes from very bright light and UV light. The newest types of eyeglasses are photochromatic so that when more UV light hits them they automatically darken to protect your eye. Sunglasses also have light polarization features. This polarization removes glare so that you can see when reflected light and glare might normally be a problem.
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.
There are many different colors used for sunglass lenses. Some colors such as yellow and brown can be used to improve your vision and others are simply used for aesthetic purposes. It is also possible to get mirror shades to hide your eyes.