Sunglasses are a form of protective eyewear designed primarily to prevent bright sunlight from damaging or discomforting the eyes. Healthcare professionals recommend eye protection whenever the sun comes out to protect the eyes against damaging UV radiation. Experts recommend sunglasses that reflect or filter out 99% of UVA and UVB light with wavelengths of up to 400 nm. Sunglasses which meet this requirement are often labeled as "UV400" The U.S. standard is called ANSI Z80.3-2001, which includes three transmittance categories. According to the ANSI standard, the lens should have a UVB (280 to 315 nm) transmittance of no more than one per cent and a UVA (315 to 380 nm) transmittance of no more than 0.3 times the visual light transmittance. There is also an ANSI standard Z87.1-2003 which includes requirements for basic impact and high impact protection. In the basic impact test, a 1 inch steel ball is dropped on the lens from a height of 50 inches. In the high velocity test, a 1/4 inch steel ball is shot at the lens at 150 feet/second. To pass both tests, no part of the lens may touch the eye.
Militti Sales & Promotions uses only the best materials in the manufacture of their sunglasses lenses. All Militti Sales & Promotions meet the above requirements for UV400 lenses. Militti Sales & Promotions Sunglasses feature two types of lenses; polycarbonate (high impact lens) and polarized (basic impact lens).
Polycarbonate material was originally designed for canopies covering cockpits in fighter planes. Polycarbonate offered an impact-resistant, optically clear window. Polycarbonate lenses for sunglasses are up to 10 times more impact-resistant than plastic or glass lenses and they provide 100% protection from the sun's harmful rays. They are also lightweight, adding to the comfort of your eyeglasses and sports eyewear. Polycarbonate lenses are the most impact-resistant lenses on the market because of its manufacturing process. The majority of other plastic lenses utilize a cast molding process. This is when a liquid plastic material is baked for long periods, in lens form, until the plastic solidifies into a lens. Polycarbonate, on the other hand, is a thermoplastic material produced from small pellets. Therefore, the earliest phase of polycarbonate lenses begin from a solid source, eliminating the cast molding process and instead use a process called inject molding in which the pellets are heated to a melting point. Once in a liquid form, the polycarbonate is rapidly injected into lens molds. At this phase in the process, the lens molds are compressed under high pressure and cooled to form a final lens product in a matter of minutes.
Polarized sunglasses first became available in 1936, when Edwin Land began experimenting with making lenses with his patented Polaroid filter. Polarized lenses improve comfort and visibility by reducing glare reflected at angles off shiny non-metallic surfaces such as water. Light reflected from surfaces such as a flat road or smooth water generally is horizontally polarized. This means that, instead of light being scattered in all directions in a more usual way, reflected light generally travels in a more horizontally oriented direction. This creates an annoying and sometimes dangerous intensity of light that we experience as glare. Polarized lenses contain a special filter that blocks this type of intense reflected light, reducing glare. Polarized sunglasses also can be worn indoors by light-sensitive people such as post-cataract surgery patients. Polarized material is more expensive than glass, plastic, or polycarbonate.