Visual clarity and comfort
Sunglasses can improve visual comfort and visual clarity by protecting the eye from glare.Various types of disposable sunglasses are dispensed to patients after receiving mydriatic eye drops during eye examinations.
Protection
Sunglasses should pass the ANSI Z87.1 requirements and offer UV protection
Excessive exposure to ultraviolet radiation (UV) can cause short-term and long-term ocular problems such as photokeratitis, snow blindness, cataracts, pterygium, and various forms of eye cancer.Medical experts often advise the public on the importance of wearing sunglasses to protect the eyes from UV. In the European Union, a CE mark identifies glasses fulfilling quality regulations. In the preparation for solar eclipses, health authorities often warn against looking at the sun through sunglasses alone.
There is no demonstrated correlation between high prices and increased UV protection. A 1995 study reported that "Expensive brands and polarizing sunglasses do not guarantee optimal UVA protection." The Australian Competition and Consumer Commission has also reported that "[c]onsumers cannot rely on price as an indicator of quality".One survey cited below even found a $6.95 pair of generic glasses with slightly better protection than Salvatore Ferragamo shades.
More recently, high-energy visible light (HEV) has been implicated as a cause of age-related macular degeneration, and some manufacturers design to block it. Sunglasses may be especially important for children, as their ocular lenses are thought to transmit far more HEV light than adults (lenses "yellow" with age).
Some sunglasses also pass ANSI Z87.1 requirements for basic impact and high impact protection. These are voluntary standards, so not all sunglasses comply, nor are manufacturers required to comply. In the basic impact test, a 1 in (2.54 cm) steel ball is dropped on the lens from 50 in (127 cm). In the high velocity test, a 1/4 in (6.35mm) steel ball is shot at the lens at 150 ft/s (45.72 m/s). In both tests, no part of the lens can touch the eye.
Standards
There are three sunglass standards.
The Australian Standard is AS 1067. The five sunglass ratings under this standard are based on the amount of light they absorb, 0 to 4, with “0” providing some protection from UV radiation and sunglare, and “4” a high level of protection.
The US standard is ANSI Z80.3-1972. According to the ANSI Z80.3-2001 standard, the compliable lens should have a UVB (280 to 315nm) transmittance of no more than one per cent and a UVA (315 to 380nm) transmittance of no more than 0.5 times of the visual light transmittance
The European standard is EN 1836:2005. The four ratings are 0 for insufficient UV protection, 1 for sufficient UV protection, 2 for good UV protection and 3 for full UV protection.
Water sunglasses
Water sunglasses, also known as surfing sunglasses, surf goggles and water eyewear consist of eyewear specially adapted to be used in turbulent water, such as the surf. Features normally available includea) shatter proof & impact resistant lensesb) strap or other fixing to keep glasses in place during sporting activitiesc) buoyancy to stop them from sinking should they be displaced from the wearerd) nose cushione) vent or other method to eliminate fogging
Many sports utilize these sunglasses including surfing, windsurfing, kiteboarding, wakeboarding, kayaking, jet skiing, Bodyboarding, and water skiing.
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