Sunglasses

Sunglasses are a specialized form of protective eyewear. They are primarily designed to prevent bright sunlight from damaging or discomforting the eyes. Beyond mere protection, they can also function as visual aids. Some versions feature lenses that are colored, darkened, or polarized to improve how a person sees the world.

Because they manage light, they are essential for both health and comfort in bright environments.

The mechanism of protection involves filtering specific parts of light. The most critical function is blocking ultraviolet radiation, often called UV radiation. Experts recommend sunglasses that filter out 99% or more of UVA and UVB light. These are often labeled as "UV400" because they block wavelengths up to 400 nm.

Another important function is managing high-energy visible light, or HEV light. Some manufacturers now design lenses specifically to block this blue light. This is particularly important for children, as their ocular lenses may transmit more HEV light than those of adults.

Different types of lenses offer different benefits. Polarized sunglasses use a special filter to reduce glare. Glare is the bright light that reflects off non-metallic surfaces like water or roads.

By reducing this reflected light, polarized lenses allow a person to see more clearly into water or down a sunny road. Other sunglasses focus on shade and color. For example, some people use amber-tinted lenses to manage light sensitivity. However, it is vital that dark lenses also block UV radiation. If dark lenses do not block UV, they can be more harmful than wearing no protection at all. This happens because the darkness causes the pupil to open wider, allowing more unfiltered radiation into the eye.

Physical design also plays a role in how well sunglasses work. A good fit is a visible way to test quality. The lenses should sit close enough to the face to block "stray light." This is light that enters from the sides, above, or below the lenses.

To prevent this, sunglasses often feature broad temple arms or leather blinders. These components act as shields to ensure light only enters through the protected lens area.

The history of eye protection stretches back many centuries. As early as the 13th century, Inuit people crafted snow goggles. These were made from flattened walrus or caribou ivory and featured narrow slits. These slits blocked harmful reflected rays to prevent snowblindness. In China, 12th-century users wore Ai Tai, which means "dark clouds." These were made from flat panes of smoky quartz. Chinese judges used these crystal glasses to hide their facial expressions while questioning witnesses.

Later, in the 18th century, Venetian women wore "gondola glasses." These were tinted, mirror-like frames used to shield eyes from the glare of canal water.

Modern sunglasses emerged through various scientific and commercial milestones. In 1772, the scientist Antoine Lavoisier was depicted wearing tinted glasses while working with amplified sunlight.

By 1899, the company Rodenstock GmbH produced glasses intended specifically to shield eyes from UV light. In 1929, Sam Foster produced inexpensive mass-produced sunglasses made from celluloid. He sold them on the Atlantic City Boardwalk under the name Foster Grant.

By 1936, Edwin H. Land began experimenting with the patented Polaroid filter, leading to polarized sunglasses. In 1937, approximately 20 million sunglasses were sold in the United States alone.

Today, sunglasses are both a medical necessity and a global industry. They are mandatory for patients immediately following surgical procedures like LASIK. They are also recommended for use in dusty areas or when using computer monitors after LASEK. The industry is massive, with Xiamen, China, serving as the world's largest producer. As of 2008, its port exported 120 million pairs of sunglasses each year. From protecting pilots in the aviation sector to helping movie stars, sunglasses have become permanent cultural icons.