Polycarbonate material was originally made for use on canopies covering fighter planes and then made its way into space on astronaut visors and space shuttle windshields. Today it is easily available to the public. Its impact resistance makes the material extremely suitable for sports, industrial safety goggles, and children's eyewear.
The reason for polycarbonate lenses' impact resistance is because of their "softness". Softer materials will flex instead of fragment when met with great force. However, the property allows lenses to be scratched easily. Therefore, every single one of our polycarbonate lenses is multi-coated with hard coatings that form a protective layer around the lenses allowing the lenses to be free from scratches while retaining their impact-resistant qualities.
Polycarbonate lenses inherently carry full UV 400 protection.
Anti-Scratch coating on eyeglasses is a coating that is applied to lens surfaces. It helps to prevent minor scratches that can easily happen to regular lenses. These minor scratches can damage the surface of the lenses and impair vision. An anti-scratch coating acts as a protective layer thus making the lenses more durable and safer.
When light meets a lens, three things happen. Some light passes through a lens, which is called refraction, some are absorbed and converted into heat, and the rest is reflected off. Glare is produced when light bounces off the lens. Glare or reflections can be annoying and in some serious cases can reduce vision. To improve vision through the appearance of the lenses and glasses, an anti-reflective coating (also known as AR coating) is used.
UV Coating is a beneficial lens treatment. It is an invisible dye that blocks ultraviolet (UV) light. Just as sunscreen keeps the sun's UV rays from harming your skin, UV-protective treatments on eyeglasses lenses block those same rays from damaging your eyes.
PD is the distance between your two pupils in millimeters. Having a correct PD on your glasses ensures that you are looking through the ideal spot in your lenses. If there is no PD on your prescription, you can check it with your doctor or measure it yourself.
Sphere(SPH) refers to the refractive correction in the prescription. Minus(-) values are for nearsightedness, and Plus(+) values are for farsightedness. If "PL" or "Plano" is written for the either SPH on your prescription, then you should select "0.00".
CYL(Cylinder) & Axis
Cylinder(CYL) refers to astigmatism. It can be either positive(+) or negative(-). Axis is recorded as an angle in degrees, between 0°and 180°. Therefore, if there is a CYL value on your prescription, then there must be an Axis for it.
If "DS" or "SPH" is noted for the either CYL on your prescription, it means you have no astigmatism.
The number sometimes written as "NV" or "Reading Addition" refers to near vision and is used for multifocal lenses and readers.
Prism is power, measured in diopters, used to correct vision displacement, like double vision or an eye turn. Most eyeglass prescriptions do not have prism correction. A prescription with prism will have two values per eye: a Prism (power) and Base (direction).
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