The requirements for<unk>  varies depending on the use. Some examples: * Cold weather: Most modern cold-weather<unk>  have two layers of lens to prevent the interior from becoming "foggy". With only a single lens, the interior water vapor condenses onto the lens because the lens is colder than the vapor, although anti-fog agents can be used. The reasoning behind the dual layer lens is that the inner lens will be warm while the outer lens will be cold. As long as the temperature of the inner lens is close to that of the interior water vapor, the vapor should not condense. However, if water vapor gets between the layers of the lens, condensation can occur between the lenses and is almost impossible to get rid of; thus, properly constructed and maintained dual layer lenses should be airtight to prevent water vapor from entering between the lenses. * Swimming: Must be watertight to prevent water, such as salt water when swimming in the ocean, or chlorinated water when swimming in a pool, from irritating the eyes or blurring vision. Allow swimmers to see clearly underwater. They will not be usable more than a few feet underwater, because the water pressure will press them tightly against the face. (Below this limit, a diving mask must be used, which allows the user to equalize pressure by exhaling air through the nose.) Examples of these include Swedish<unk> . * Power tools: Must be made of an unbreakable material that prevents chunks of metal, wood, plastic, concrete, and so on from hitting or piercing the eye, usually polycarbonate. Usually has some sort of ventilation to prevent sweat from building up inside the<unk>  and fogging the surface. * Blowtorch<unk> : These protect the eyes from glare and flying sparks and hot metal splashes while using or near a blowtorch. They are not the correct filters for arc welding. * Welding<unk> : Includes all<unk>  for eye protection during welding or cutting. They provide protection against debris, the heat from welding, and, with the proper filters, the optical radiation resulting from the welding, which can otherwise cause arc eye. * Motorcycle riding and other open-air activities: Prevents insects, dust, and so on from hitting the eyes. * Laboratory and research: Combines impact resistance with side shields to prevent chemical splashes reaching the eyes. May also include laser protection which would be covered by EN 207 (Europe) and ANSI Z 136 (United States). Examples of these include red adaptation<unk> . * Racquetball: Protect the eyes from racquets swinging in an enclosed area and from impact from hard rubber ball. * Winter sports: Protect the eyes from glare and from icy particles flying up from the ground. Double lens anti-fog ski<unk>  were invented and patented by Robert Earl "Bob" Smith. Visible Light Transmission (VLT) or S value describes the percentage of light allowed through the lens. * Astronomy and meteorology: dark adaptor<unk>  are used before going outside at night, in order to help the eyes adapt to the dark. * Basketball: Several NBA players have worn<unk>  during play, including Kareem Abdul-Jabbar, James Worthy, Horace Grant, Kurt Rambis and Amar'e Stoudemire; they prevent a fellow player from scratching or hitting the eyes when trying to grab the basketball. In most circumstances, a player starts wearing protective<unk>  to prevent further injury to the eyes. * Aviation: In open cockpit aircraft, such as old biplanes, aviators, such as Amelia Earhart and Charles Kingsford Smith, would wear<unk>  to help protect from the wind and are still in use today. Examples of these include the AN-6530<unk> . * Virtual reality: A virtual reality headset, sometimes called<unk> ", is a wrap-around visual interface to display computer output. Commonly the computer display information is presented as a three-dimensional representation of real-world environments. * Drunkenness:<unk>  designed to simulate the vision altering effects of psychoactive drugs, in particular alcohol. Examples include Fatal Vision<unk> . There are no studies that have found beneficial effects of use of fatal vision<unk>  on the likelihood that individuals will later engage in impaired driving.
Goggles
Eye dropper
Frenzel goggles
Windsor glasses
Contact lens
Browline glasses
Bionic contact lens
Pinhole glasses