Facts About Eye Glasses

Eyeglasses are needed to help people see better. If you have prescription glasses, you may need to wear them all the time or only for tasks such as reading, driving and watching movies. Spectacles usually consist of a pair of lenses that correct vision and a frame that holds the lenses together and helps them to sit in front of your eyes.

History

• No one knows who invented the first spectacle lenses. Roman tragedian Seneca (4 B.C.-A.D. 65) is said to have read "all the books in Rome" by looking through a glass globe of water, according to didyouknow.org. Monks in the middle ages used glass spheres to magnify and read. Philosopher Roger Bacon made the first known scientific commentary on lenses for vision correction in writing in 1268.

  Venetian glass blowers are known to have put glass into hand-held, single lens-type frames made of horn or wood in the 13th century. Benjamin Franklin is credited with inventing bifocals in 1784.

Types

• Eyeglasses can be made with single lenses that correct for distance or up close, or they can be made with multifocal lenses, which correct for distance and reading. These also are called bifocals. Bifocals can have obvious lines or the lines can be blended or made to appear invisible.

  Glasses can be made for safety and sports, for sun wear and for specialty jobs. There are special lenses made for people who need to be able to see up close while looking up, such as pharmacists and plumbers, or at a unique distance, such as musicians who need to read sheet music at arm's length.

Frames

• Spectacle frames usually are made of plastic or metal. Plastic frames are made from zylonite, cellulose acetate or nylon. Zylonite, also called zyl, is the most common type of plastic frame because it is lightweight and inexpensive. Metal frames can be made from many different materials, including aluminum and stainless steel. In recent years, titanium frames have become popular because of the strength and durability of the material. Titanium frames are lighter, corrosion-resistant and hypoallergenic, according to Ray-Ban.com.

Lenses

• Lens material for glasses can be made of glass, plastic or polycarbonate. Glass was the original material for spectacles and has great optical clarity, but the lenses can become heavy in stronger prescriptions. Plastic lenses are much lighter than glass but can scratch easier. Polycarbonate, also called CR-39, is the lightest and thinnest lens material. CR-39 also is the most shatter-resistant type of lens. Newer hybrid and specialty lenses can correct for extremely strong prescriptions. Aspheric lenses are made for people who are extremely farsighted, using less obvious magnification and allowing for better cosmetics and less distortion for the wearer, according to allaboutvision.com. Hi-index lens material is a cross between plastic and glass, which makes the lenses lighter and less thick and help people who are extremely nearsighted.

Prescriptions

• To purchase a pair of glasses, you will need a prescription from an eye doctor. Although you can purchase over-the-counter glasses, these are usually made with inferior quality material and the lenses may have distortion. In addition, many people have complex and individual prescriptions that can not be purchased as ready-made. To make sure you are seeing as good as possible, the American Optometric Association recommends having your eyes examined every one to two years.

Recycle

• Your old glasses can be recycled. Groups such as the Lions Club and Global One Sight collect and refurbish previously worn glasses and distribute them to people in need around the world. Most eye doctors or retail optical outlets have collection boxes for old glasses.