Eye care
Lens Materials
There are many single vision lens materials, but the most commonly used polymer is a plastic material known as CR-39. Because of its light weight, it is very comfortable and can be tinted almost any color and density.
However, certain manufacturers of CR-39 lenses produce a low quality and inferior product. Often, the lenses will be warped, causing 'soft spots' of poor vision throughout the lenses.
Manufacturers that create exceptionally high optical quality lenses, all of which can be ordered with a very effective scratch protection coating, are SEIKO, SILOR and SOLA.
Thin-plastic (hi-index) and light lenses are also available. The refractive index of this material is higher than regular plastic lenses. This means that a thinner lens can do the same job that a thicker lens would normally do. These lenses are about 35% thinner and lighter than regular plastic lenses.
Be aware, however, there are different grades and qualities of these lenses. The higher the refractive index, the thinner the lens.
The best quality hi-index lenses have a refractive index of 1.60 or 1.66. Some opticals still use lenses with a 1.54 refractive index, but charge the price of a 1.60 lens, because John Q. Public doesn't know the difference. If your prescription requires hi-index lenses, insist on 1.60 or 1.66 refractive hi-index lenses for best quality and thinnest lenses.
We recommend the following hi-index lenses:
- Silor Thin & Lite 1.60 refractive index
- Pentax THC 1.60 refractive index
- Pentax 1.66 Ultrathin with anti-reflective
- Seiko Super 16 MX
- Seiko Super 16 diacoat
- Optima Aspheric 1.66
- Optima Aspheric 1.60
- Optima Hyper 1.60
- Any Sola product
Another material, called Polycarbonate, is often marketed as a thin and light lens. It is softer than CR-39, may scratch and can't be tinted as dark as plastic lenses. It definitely is lighter and thinner than regular plastic. Many opticals promote this material over hi-index because it costs less, yet they often charge the same price as hi-index lenses.
Polycarbonate is extremely resistant to shattering, so it is recommended for children or persons needing safety eye protection. However, the newerhi-index lenses sometimes have superior optics compared to polycarbonate which occassionally has some peripheral distortion. If you are being sold a thinner and lighter lens, ask if it is polycarbonate or hi-index plastic.
REMINDER: POLYCARBONATE AND HI-INDEX PLASTIC LENSES AUTOMATICALLY COME WITH SCRATCH PROTECTION AND ULTRAVIOLET PROTECTION. IF YOU PURCHASE EITHER ONE OF THESE TWO MATERIALS DO NOT BE SOLD THESE COATINGS AS 'ADD-ONS.'
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