There are two features that all BrightEyes' Sunglasses share in common. All the sunglasses we carry have optically correct lenses and provide 100% UV protection.
An optically correct lens prevents headaches after wearing for an extended period of time. When the eye has to look through a lens that is not optically correct, it has to continually refocus because of distortion. This places a large amount of strain on the eye and can eventually lead to headaches, nausea and dizziness.
Sunglass lenses are made of three different materials:
CR39 stands for Columbia Resin batch 39 manufactured by the Pittsburgh Plate Glass company, which had laboratories in Columbia, this is made up of hard cast resin (CR).
- Half the weight of glass lenses.
- Much more shatter-resistant (but not shatter-proof).
- Consistent colour no matter the thickness (preferable for prescription lenses).
- Can be ground and polished like glass.
- Must be dyed to achieve colour; dyes are not as permanent.
- Tint consistency is difficult to achieve.
- Scratch easier than glass, even with scratch-resistant coating.
- Susceptible to colour and coating fading (thermal bleaching) when exposed to heat.
- Can warp when exposed to excessive heat (>120ºC)
Polycarbonate materials are very similar to CR39 materials, although the molecular structure of the lens does differ and contributes to a much more impact resistant material. It is a remarkably strong plastic; in fact, aircraft windshields motorcycle windshields and sport safety glasses are made of polycarbonate.
A good choice for people who engage in outdoor activities and fast-action sports.
- The most shatter-resistant lenses available.
- Very lightweight. (approx 27% lighter than CR39)
- Preferred for oversized lenses to wrap around the face.
- Highest absorption of UV
- Naturally very soft material, it must be coated for scratch resistance.
- Least scratch-resistant material (even with coating).
- Can not be tinted.
The clearest of the three lenses ground and polished like a fine camera lens, so the surface is free of imperfections. These days’ glass lenses make up a very small percentage of the sunglass market.
- Provides the best scratch resistance.
- Permanent tint and UV protection can be added during manufacture.
- Can have an anti-reflection coating to help with glare reduction.
- Can be vacuum coated with tint (a more permanent method).
- Least shatter-resistant material.
- Tints can be darker in thicker areas or lighter in thinner areas (as in prescription lenses) due to tint being a coating on surface.
- Shapes are limited due to weight and size.
- Twice as heavy as plastic.
- You can not coat a finished glass lens.
- Fogs up more easily.
- Tints are limited in colour and depth.