Guide for Eyeglass Lens

What is a plastic lens?  CR-39, frequently called plastic lenses, are the most common lenses sold. These lenses have replaced glass lenses because they are lighter in weight and result in a much more comfortable pair of glasses.

What is a polycarbonate lens? Polycarbonate lenses are half the weight of a regular CR-39 lens (plastic). They are harder to break and more shatter-resistant than other lens materials, making them the lens of choice for children's lenses and for sports. While polycarbonate lenses offer several advantages, the visual clarity is not as high as a plastic lens.

What is a glass lens? Glass lenses are still made today but are not sold as often. Glass lenses are twice the weight of a common CR-39 lens, more likely to break or shatter, and have to be cut at a specialty lab resulting in a longer time for manufacturing.

What is scratch coating? This is a coating to help with the everyday wear and tear on lenses. It does help prevent scratches from normal use and cleaning, but does not make lenses scratch proof.

What is anti-reflective coating? This coating provides clearer sharper vision and eliminates unwanted glare. Anti reflective coatings reduce the visual discomfort caused by glare from oncoming traffic at night, indoor overhead lights, and extended computer use. Many of the newer anti-reflective coatings offer the added benefits of resisting smudges or fingerprints and being much easier to clean.

What is UV protection? This clear coating protects your eyes from the harmful ultraviolet rays given off by the sun. If you are exposed to the sun for long periods of time, the UV filter will protect your eyes from irreversible damage.

What is a photochromic or Transitions lens? Transition® lenses (photochromic lenses) are a great option for people that are sensitive to sunlight. These lenses are clear at night or when indoors, and darken when exposed to UV rays from the sun.

What is a polarized lens? Polarized lenses are sunglass lenses that reduce the glare from the sun reflecting off of objects such as water or car windshields. Polarized lenses allow you to see the truest colors while providing the best vision, comfort, and protection from the environment. As a result, these lenses reduce eye strain and increase visibility.

What is tint? Lenses can be dyed with a tint to reduce light transmission or for a fashionable appearance. Tints can be light, dark or gradient and are available in most colors.                         

http://www.allaboutvision.com/lenses/coatings.htm

Anti-Fog Coating At least one eyeglass lens coating company (Opticote) has created a permanent coating designed to eliminate this problem. The factory-applied coating — called Fog Free — eliminates the condensation of moisture on lenses that causes fogging.

Regular plastic eyeglass lenses block most UV light, but adding a UV-blocking dye boosts UV protection to 100 percent for added safety. Other eyeglass lens materials, including polycarbonate and most high-index plastics, have 100 percent UV protection built-in, so an extra lens treatment is not required for these lenses.

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These lenses are made of plastic and are extremely light in weight. They have a scratch resistive coat on them so that they do not get easily scratched and also over it they have an Anti reflective coating which prevents the light from getting reflected. The ARC coating also acts as a additional UV filter and also a shield to resist scratches. They are 97% scratch resistant as easy to handle. These lenses are very light compared to glass lenses. They have a normal index which denotes that these lenses are of the basic thickness. These lenses are used for presbyopic patient, age above 40 years. . Progressive spectacle lenses, also called progressive addition lenses (PAL), varifocal or multifocal lenses. Progressive spectacle lenses, also called progressive addition lenses (PAL), varifocal or multifocal lenses. These are used to correct presbyopia. The gradient starts at the wearer's distance prescription, at the top of the lens and reaches a maximum addition power, or the full reading addition, at the bottom of the lens. In wide design progressive intermediate and the reading zone is more compare to standard design progressive lenses and the temple side vison distortion is also less. . these are very comfortable for mostly used for computer users because of wider vision zone.The photochromic nature of these lenses make them turn dark in sunglight and provide the patient with complete uv protection from sunlight. They also give immense cooling to the patients eyes and eliminates glare while driving in sunlight. http://www.lensmakers.in/Products/Lenses-Spectacle-Lenses-Progressives/Lensmakers/EVA-PROGRESSIVE---WIDE-DESIGNNORMAL-INDEXPHOTOCHROMIC-GRAYARC-COATED/pid-837815.aspx  http://www.lenskart.com/

in any case professional guidance is safe