What is the difference between glass and plastic lenses?
Plastic lenses are 50% lighter, more impact resistant, more resistant to pitting and fogging, and very tintable. They also offer about 80% UV protection. Glass lenses are more resistant to surface abrasions, but they provide only minimal UV protection.

What are polycarbonate and hi-index lenses?
Polycarbonate is a type of hi-index plastic originally developed by NASA for use in astronauts? face shields because the material is shatter-resistant. In addition to being the safest and most impact resistant lenses on the market, polycarb lenses also absorb 100% of harmful UV rays. They are the best options for use in children?s glasses, sports, and safety goggles. They are also lighter and thinner than regular plastic lenses.

Hi-index lenses are made of ?dense? materials that refract (bend) rays of light more effectively, thereby enabling the lenses to be up to 45% thinner than conventional lenses. Thus, for the same prescription, hi-index lenses will be thinner, lighter, and more cosmetically appealing. There are both hi-index glass and plastic lenses available, though hi-index glass is much heavier. In addition, hi-index materials inherently block 100% of harmful UV light. Keep in mind that surface reflections off the lens increase as the index of the lens material increases. Thus, it is recommended to have anti-reflective coating on hi-index lenses.

What are aspheric lenses?
These lenses provide visual and cosmetic benefits for high prescriptions. They are flatter than conventional lenses and have their thickness more evenly distributed over the entire lens. This provides for more clarity and reduces the ?coke bottle? effect of conventional thick lenses. Aspheric lenses can be combined with hi-index technology for the ultimate in attractive thin lenses.

Should I get UV coating on my lenses?
Yes. The ultraviolet rays found in sunlight can cause potential harm to the eyes. Special treatment is available for glass and plastic lenses that completely blocks hazardous UV light. Lenses such as polycarbonate, hi-index, and photochromic lenses include built-in UV protection at no extra cost.

What is scratch resistant coating (SRC)?
SRC minimizes hairline scratches on plastic lenses, but it does not prevent scratching. All polycarbonate and hi-index plastic lenses automatically have SRC applied to them.

What is anti-reflective coating (ARC)?
ARC is a coating on the lens surface designed to reduce surface reflections and to improve clarity, comfort and cosmesis. People will experience better vision with ARC due to its ability to reduce glare caused by intralens reflections. This is most evident while performing tasks such as night driving and computer use. ARC is also helpful in very near-sighted prescriptions because it reduces the edge reflections caused by the thicker outside edges of the lenses.

Should I apply both SRC and ARC to a lens?
No. ARC is the last coating applied to a lens, so it would cover any SRC already on the lens. This defeats the purpose of SRC, so it is not necessary to apply both coatings. ARC inherently has scratch-resistant properties.

Can you apply a tint to an ARC-coated lens?
No. This will destroy the ARC. In order to change the tint, you need to decoat the lens of the ARC, tint the lens to the desired color, and then recoat with ARC.

What are photochromic lenses?
These are lenses that darken automatically as you go from indoors to outdoors. This lens darkening is activated by UV light. They are available in plastic, glass, or polycarbonate.

What are the advantages of having a tint to my lenses?
Tints can enhance visual comfort and performance. They are also used widely for cosmetic and fashion purposes. Regular plastic and hi-index lenses can be tinted to any shade or color. Glass lenses are more difficult to tint and don?t always tint uniformly. For tintable polycarbonate lenses, the tint is absorbed into the back coating only. Therefore, polycarbonate lenses cannot be tinted to the same density as regular plastic lenses.

Can old prescription lenses be tinted for use as sunglasses?
For SRC-coated lenses greater than one year old, this procedure is not recommended because breaks may have developed in the SRC. This may give rise to streaky, uneven tinting. If the lenses are regular plastic and uncoated, then they can be tinted for use as sunglasses. However, it is important to also treat the lenses with UV protection if they are to be used outdoors, since the tint itself does not offer complete protection from UV rays. Only tints designed to specifically block UV light offer complete protection.

What are polarized lenses and what advantages do they have?
Polarization is a special filtering process, like a screen door, that filters out reflected light. It cuts down glare significantly, and it is recommended for anyone who participates in many high-glare activities such as skiing, swimming, fishing, sailing, etc. Polarized sunglasses provide the wearer with the best comfort and clarity possible under bright, high-glare conditions. Lenses that are polarized will be marked as such.

Tips for people with high prescriptions:
Because conventional high prescription lenses are thick, consider the following to reduce lens thickness:
1. Smaller frame size
2. Aspheric design
3. Hi-index lenses