The term safety glasses describes several types of eyewear. Industrial and work glasses, impact-resistant lenses for everyday use, and sports frames or glasses used for protection are all considered safety glasses.
Significance
Safety glasses help prevent eye injuries. According to the Occupational Safety and Health Administration, eye injuries cost people in the United States hundreds of millions of dollars annually. To be considered industrial safety glasses, the lenses and frames must conform to more stringent regulations of impact resistance than everyday or department store safety glasses.
Types
Prescription safety lenses are available in polycarbonate, glass or plastic material. Most safety lenses are polycarbonate, which is the most shatter-resistant type of lens, but no lens is completely shatter-proof. Safety frames are made from plastic or metal.
Considerations
To be approved as safety glasses in a manufacturing or work environment by OSHA, lenses must be a certain thickness and pass one of two tests. The first, basic test is called a "drop ball test." According to the Food and Drug Administration, this test is done with a 5/8 inch steel ball dropped from a height of 50 inches onto the center surface of a lens. To be considered safe, the lens must not fracture or chip during either test. The second test is a high-impact test done by shooting a 1/2 inch steel ball at the lens. Frames must have a specific type and size bevel, which is the part of the frame that holds the lens in place and keep the lens from fracturing toward the eye in case of impact. Safety frames also go through testing.
Identification
Safety glasses have marks to identify them as approved for safety. A lens that has passed the high velocity test is engraved with a "+" mark on the lens. Lenses with tint will have an "s" or a "v" for a tint that gets lighter and darker. Safety frames are marked "Z87-2" if they are prescription glasses and non-prescription frames are engraved "Z87" or "Z87+" if they are high impact.
Warning
Eyeglasses should not be worn if any type of chip or crack is in the lenses. Any damage, even just a tiny crack, can cause a lens to break and cause serious harm.
