Sunglasses provide protection against excessive exposure to light, including its visible and invisible components.
The most common protection is against ultraviolet rays, which can cause short and long-term eye problems such as photokeratitis, snow blindness, cataracts, pterygium, and various forms of eye cancer. Medical experts advise the public on the importance of wearing sunglasses to protect the eyes from UV rays; For adequate protection, experts recommend sunglasses that reflect or filter 99% or more of UVA and UVB light, with wavelengths up to 400nm. Sunglasses that meet this requirement are often labeled “UV400”. This is a bit more protection than the widely used European Union standard, which requires that 95% of radiation up to 380nm only be reflected or filtered.
Sunglasses are not enough to protect the eyes from permanent damage caused by looking directly at the sun, even during a solar eclipse. Special glasses known as solar viewers are needed for a direct view of the sun. This type of glasses can filter UV rays that are harmful to the eyes.
More recently, high energy visible light has been implicated as a cause of age-related macular degeneration; Previously, debates had already existed on whether “bluish” or tinted amber glasses could have a protective effect. Some manufacturers are already designing glasses to block blue light; insurance company Suva, which covers most Swiss employees, has asked eye specialists around Charlotte Remé to develop standards for blue blocking, leading to a recommended minimum of 95% blue light.
Sunglasses are especially important for children because their eye lenses are believed to transmit much more HEV light than adults.
There has been speculation that sunglasses promote skin cancer. This is because the eyes are made to produce less melanocyte-stimulating hormone in the body.