Sunglasses are protective eyewear designed to shield the eyes from damaging or discomforting sunlight and high-energy light. They can also work as a visual aid. The ultraviolet radiation from the sun can cause several serious eye problems and many healthcare professionals recommend eye protection. However, since the 1940s sunglasses have been associated with celebrities more so than eye protection.

James Ayscough experimented with tinted lenses in the mid-18th century although they were not “sunglasses”. They were designed as vision correction since it was believed that blue or green tinted lenses could correct vision impairments. Since sensitivity was commonly a symptom of syphilis brown and amber tinted spectacles were commonly prescribed in the 19th century.

By the early 1900s sunglass became more widespread especially amongst stars of silent movies. Originally it was thought they did this to hide from fans, however, it was truly the powerful arc lamps causing them to have perennially red eyes. Sam Foster introduced inexpensive mass-produced sunglasses to America in 1929. Edwin H. Land introduced polarized sunglasses in 1936 by making lenses with his patented Polaroid filter. These types of sunglasses are popular amongst fishermen since the polarization protects the eyes from the glare.

The sunglasses offer widespread protection against ultraviolet radiation which is known to cause short and long-term ocular problems. It is recommended that a person wear sunglasses that reflect or filter out 99-100% of UVA and UVB light. Glasses that meet this requirement are often labeled as “UV 400.” Sunglasses are not sufficient to protect the eyes against permanent harm from looking directly at the sun.

There is some debate as to whether sunglasses actually promote skin cancer by tricking the eyes into producing less melanocyte-stimulating hormone in the body. The effectiveness of the glasses is based on the protection the lens provides and fall within various classifications of UV protection.

The glasses should fit close enough to the face that only very little “stray light” can reach the eye from the sides. Just because lenses are dark they do not necessarily offer more protection than light lenses. In fact they can cause more damage by causing the pupil to open wider allowing more unfiltered radiation to enter the eye.
Sunglasses are sometimes used to hide one’s eyes, which makes eye contact impossible and can be intimidating to those not wearing sunglasses. They are also used to hide abnormalities, visual impairment. Many of the blind where them not due to embarrassment but due to making others feel uncomfortable.

There are three major sunglass standards for reference to sunglass protection from UV radiation; however these standards also include further requirements. There is an attempt to make a worldwide ISO standard however these are not mandatory.

The Australian, European, and American standards all vary; however, in 2003 the Australian standard was updated and made to be relatively similar to the European standard.

For recreational use glasses and sunglasses have to meet special requirements and need to be shatterproof and impact-resistant. When mountain climbing or traveling across glaciers or snowfields sunglasses need to provide better protection due to the light reflecting off the snow. These goggles usually have dark, round lenses and leather blinders at the sides. Astronauts also need a higher level protection since the UV rays are not filtered through the atmosphere.

The first sunglasses used in a Moon landing were the original Pilot Sunglasses made by American Optical. James B. Stephens and Charles G. Miller created special lenses that protected against the light in space or the light during laser and welding work.